# Me thods of A n a l y s is by the U.S. Ge ologic a l Surv e y Na tiona l Wa te r Qua lity La bora t ory

— De te rmina tion of Pesticides in Water by Gra phitized Carbon-Based SolidPh ase Extractio n an d Hig h

- Perfo rman ce L i q u i d

Ch ro mato g r ap h y /Mass Sp ectro metry

W a ter-Resources Investigations Report 01–4134

U.S. Department of the Interior U.S. Geological Surv ey

# Me thods of A n a l y s is by the U.S. Ge ologic a l Surv e y Na tiona l Wa te r Qua lity La bora t ory

— De te rmina tion of Pesticides in Water by Gra phitized Carbon-Based SolidPh ase Extractio n an d Hig h

- Perfo rman ce L i q u i d

Ch ro mato g r ap h y /Mass Sp ectro metry

By Edw a rd T. Furlong, Bruce D. Anderson, Stephen L. W e rner, Paul P. Soliv en, Laura J. Co ffey

, and Mark R. Burkhardt

U.S. Geological Surv ey

W a ter-Resources Inv e stigations Report 01–4134

Denver, Colorado

2001

## U. S. Depar t ment of the I n ter i or Gale A

. Norton, Secretary

U. S. Geol ogi cal Sur v ey Charles G. Gr oat, Di r ector

T he us e of tr ade, pr oduc t, or f i r m nam es in this r epor t is f o r des c r iptive pur pos es only and

does not im ply endor s e m ent by the U.S. G o ver n m ent.

F o r additional inf o r m ation w r ite to: Copies of this r epor t c an be pur c has ed f r om :

Chief

, National W a ter Q uality Labor ator y U.S. G eologic a l Sur v ey U.S. G eologic a l Sur v ey Br anc h of Inf o r m ation Ser v ic es Box 25046, Mail Stop 407 Box 25286

F eder al Center F eder al Center

Denver , CO 80225- 0046 Denver , CO 80225- 0286

## CONTENTS

Abst ract 1

I n troduction 1 Analy tical Method 3 1. Application 3

2. Summary of method 8

3. I n t e rferences 9

4. Apparatus and instrumentation 9

5. Reag ents and solutions 11

6. S a fet y precaut i ons 19

7. Procedure 20

8. Calculations 35

9. Reporting of results 37

10. Quality assurance/quality control 37

11. Method performance 39

Conclusions 71

R e ferences ci t e d 72

FIGU R ES

1. Chromatog r am of a positive ion standard used in this method 26

2-6. Graphs of recoveries showing : 2. Compounds fortified at three leve ls in org a nic-free water and determined under positive ioniz a tion conditions 59

3. Compounds fortified at three leve ls in g r ound-water samples and determined under positive ioniz a tion conditions 60

4. Compounds fortified at three leve ls in surface-water samples and determined under positive ioniz a tion conditions 61

5. Compounds determined under ne g a tive ioniz a tion conditions 62

6. Median recoveries of met hod compounds from 285 laboratory

reag ent spikes determined fro m October 1, 1999, to September 30, 2000 66

TA B L ES

1. Compound names, uses, pesticide class, Chemical Abstract Service reg i stry numbers, and codes 4

2. Calibration solution composition for compounds determined under

neg a tive ioniz a tion conditions 14

3. Calibration solution composition fo r compounds determined under positive

ioniz a tion conditions 15

4. Surrog a te solution composition for compounds determined under positive and neg a tive ioniz a tion conditions 17

5. Volume dilutions for method working standards 18

6. W o rking standard concentrations and equivalent sample concentrations

for this method 19

7. Hi g h -perform ance l i qui d chrom a t o g r aph mobile-phase g r adient

for this method 27

CONT E N T S I I I

### 8. Ma ss spe c t r o me te r ope r a ting c onditions dur ing positive a nd ne g a tive

ioniz a tion anal y s es used in this method 27

9a. Mass spectrometer time-p rog r ammed operating cond itions for individual compounds determined u nder positive ioniz a tion conditions 28

9b. Mass spectrometer time-prog r ammed ope rating conditions for individual compounds determined u nder ne g a tive ioniz a tion conditions 29

10. Quantitation and confirma tion ions used for the compounds determined

in this me thod 30

11. Autotune paramet e rs for acc eptable tuning criteri a used in this method 31

12. Ty pical minimum sample analy s is se quence for hig h -pe rformance liquid

chromato g r aph y /mass sp ectrometr y anal y s is in this method 34

13. Accuracy and precision data from 10 determinations of the method compounds fortified at 0.025 microg r am pe r liter in org a nic-free water, under positive ioniz a tion condit i ons 42

14. Accuracy and precision data from 10 determinations of the method compounds fortified at 0.025 microg r am pe r liter in org a nic-free water, under negative ioniz a tion conditions 43

15. Accuracy and precision data from se ven determinations of the method compounds fortified at 0.10 microg r am pe r liter in org a nic-free water, under positive ioniz a tion condit i ons 43

16. Accuracy and precision data from se ven determinations of the method compounds fortified at 0.10 microg r am pe r liter in org a nic-free water, under negative ioniz a tion conditions 44

17. Accuracy and precision data from ni ne determinations of the method compounds fortified at 0.50 microg r am pe r liter in org a nic-free water, under positive ioniz a tion condit i ons 45

18. Accuracy and precision data from ni ne determinations of the method compounds fortified at 0.50 microg r am pe r liter in org a nic-free water, under negative ioniz a tion conditions 46

19. Accuracy and precision data from 10 determinations of the method compounds fortified at 0.025 microg r am pe r liter in g r ound-water samples, under positive ioniz a tion condit i ons 46

20. Accuracy and precision data from ni ne determinations of the method compounds fortified at 0.025 microg r am per liter in g r ound-water samples,

under ne g a tive ioniz a tion conditions 47

21. Accuracy and precision data from si x determinations of the method compounds fortified at 0.10 microg r am per liter in g r ound-water samples, under positive ioniz a tion conditions 48

22. Accuracy and precision data from si x determinations of the method compounds fortified at 0.10 microg r am pe r liter in g r ound-water samples, under negative ioniz a tion conditions 49

23. Accuracy and precision data from 11 determinations of the method compounds fortified at 0.50 microg r am pe r liter in g r ound-water samples, under positive ioniz a tion condit i ons 49

24 Accuracy and precision data from 10 determinations of the method compounds fortified at 0.50 microg r am per liter in g r ound-water samples,

under ne g a tive ioniz a tion conditions 51

CONT E N T S I V

### 25. Ambient pesticide concentrations measured in South Platte River

sa mple s dur ing this stud y 52

26. Accuracy and precision data from ni ne determinations of the method compounds fortified at 0.05 microg r am per liter in surface-water samples, under positive ioniz a tion conditions 53

27. Accuracy and precision data from ni ne determinations of the method compounds fortified at 0.05 microg r am pe r liter in surface-water samples,

under ne g a tive ioniz a tion conditions 54

28. Accuracy and precision data from si x determinations of the method compounds fortified at 0.10 microg r am pe r liter in surface-water samples, under positive ioniz a tion conditions 54

29. Accuracy and precision data from si x determinations of the method compounds fortified at 0.10 microg r am pe r liter in surface-water samples,

under ne g a tive ioniz a tion conditions 55

30. Accuracy and precision data from ei g h t determinations of the method compounds fortified at 0.50 microg r am per liter in surface-water samples, under positive ioniz a tion conditions 56

31. Accuracy and precision data from ei g h t determinations of the method compounds fortified at 0.50 microg r am pe r liter in surface-water samples,

under ne g a tive ioniz a tion conditions 57

32. L ong -term accuracy and precision calculate d from multiple deter minations of the method compounds fortified in sample -set spikes, with the compounds

added to or g a nic -fr ee w a ter at 0.25 micro g r am per liter 64

33. Detections of compounds in 197 set blanks anal y z ed with this method 67

34. Method detection limits for the method described in this study and the predec essor method of W e rner and othe rs (1996 ) 69

CONT E N T S V

### CONV E R S ION FA CTORS A ND A BBRE V I A T E D W A TE R-QUA L ITY UNITS

M u ltiply B y T o o b t a i n



### centim eter (cm ) 3.94 x 10 -1 

### inch

g r am (g ) 3.53 x 10 -2 

### ounce, av oirdupois

k ilopascal (k Pa) 1.45 x 10 -1 

### pounds per square inch

liter (L ) 3.38 x 10 -1 

### ounce

m e ter (m ) 3.28 x 10 0 

### foot

mi c r o g r a m ( μ g ) 3.53 x 10 -8 

### ounce, av oirdupois

m i croliter (μL ) 3.38 x 10 -5 

### ounce

m i crom eter (μm ) 3.94 x 10 -5 

### inch

m illig ram (m g ) 3.53 x 10 -5 

### ounce, av oirdupois

m illiliter (m L ) 3.38 x 10 -2 

### ounce

m illim eter (m m ) 3.94 x 10 -2 

### inch

nanog ram (ng ) 3.53 x 10 -1 1 

### ounce, av oirdupois



### Deg r ees Celsius (°C) may be conve rted to deg r ees F a hrenheit (°F ) using the following equation:

°F = 9/5 (°C) + 32.

A BBRE V I A T E D W A TE R-QUA L ITY UNITS

g / L g r a m pe r lite r

g /mL g r a m pe r millilite r kg /m 2 kilog r am per square meter

μg /L mic r o g r a m pe r lite r

μg /μL mic r o g r a m pe r mic r o lite r

μg /mL mic r o g r a m pe r millilite r μL /L mic r o lite r pe r lite r μL /mL mic r o lite r pe r millilite r

mg /L millig r a m pe r lite r

mg /mL millig r a m pe r millilite r
mL /L millilite r pe r lite r
mL /min millilite r pe r minute

ng /L na nog r a m pe r lite r

ng /μg nanog ram per microg r am

ng /μL na nog r a m pe r mic r o lite r

ng /mL na nog r a m pe r millilite r

CONT E N T S V I

### A BBRE V I A T IONS A ND A CRONYMS

a m u a t omic ma ss unit

B D MC 4-bromo-3,5-dimethy l pheny l-n-methy l carbamate

cat. no. catalog number

CCB continuing calibration blank

CCV continuing calibration verification DAD photodiode-array detection

“E” second elution fraction

F E B field equipment blank

F M S f i e l d ma tr ix spike GC g a s c h r o ma tog r a phy

GC/MS g a s c h r o ma tog r a phy /ma ss spe c t r o me tr y
HP L C hi g h -perform ance liquid chromatog r aphy

HPL C /MS hig h

- p e r f o r

m a n c e liquid c h r o ma tog r a phy /ma ss spe c t r o me tr y kV kilovolt

L OQ limit of qua ntita tion

L R B laboratory reag ent blank

L R L laboratory reporting level

L R S l a borat ory reag ent spi k e “M” fi rst (m et hanol ) elution fraction

MDL method detection limit

M H z me g a h e r t z MS mass spectrometry
m/z ma ss- to- c ha r g e r a tio NAWQA Na tiona l Wa te r

- Q ua lity Asse ssme n t Pr og r a m NWI S Na tiona l Wa te r I n f o r

m a tion Sy ste m NWQL Na tiona l Wa te r Qua lity L a bor a t or y ODS oc ta de c y lsila ne POC polar org a nic compound QA/QC qua lity a ssur a nc e / qua lity c ontr o l QC qua lity c ontr o l

RF response factor

SPE solid- pha se e x tr a c tion

TF A tr if luor oa c e tic a c i d

USEPA U.S. Environmental Protection Ag ency US GS U.S

. Geolog ical S u rvey UV ultr a v iole t
v/v volume per volume

w/v weig ht per volume

≡ i d ent i cal wi t h, cong ruent

 equals approx imately

± plus or minus

CONT E N T S V II

# Methods of Analy s is by t he U.S. Geological Survey

National W a ter Quality Laboratory

— Determination of

Pesticides in W a ter byGraphitized Carbon-Based SolidPhase Extraction and High-Performance Liquid Chromatography /Mass Spectrometry

By Edw a rd T. Furlong, Bruce D. Anderson, Stephen L. W e rner, Paul P. Soliv en, Laura J. Co ffey

, and Mark R. Burkhardt

A b st ract

I n 1996, the U.S. Geolog ical Survey

Na tiona l Wa te r Qua lity L a bor a t or y

( N WQL )

de ve lope d a nd imple me nte d a

g r a phitize d carbon-based solid-phase ex traction and hig h

performance liquid chromatog r aphic analy tical method to de termine polar pesticide

concentrations in su rface- and g r ound-water samples. Subsequently , the NW QL developed a complementary analy s is that uses hig h -performance liquid chromatog r aphy /

ma ss spe c t r o me tr y

to de te c t , ide n tif y , a nd quantify polar pestic ide s a nd pe stic ide

me ta bolite s in f ilte r e d wa te r a t c onc e n tr a tions

a s low a s 10 na nog r a ms pe r lite r

. This ne w method was desig n ed to improve sensitivity and selectivity over th e prior method, and to

reduce known interferences from natural

or g a nic ma tte r

.

I n this new method, pesticides are

e x tr a c t e d f

r o m f ilte r e d wa te r sa mple s by using a 0.5-g r am g r aphitiz ed carbon-based solidphase ex t r act i on cart r i d g e , el ut ed from t h e

cart r i d g e , and concent r a tions determined by using hig h -performance liquid chromatog r aphy with electrospray ioniz a tion–mass spectrometry

. The upper concentration limit is 1.000

mic r o g r a m pe r lite r ( μ g / L ) f o r

most c o mpounds. Sing le-operato r method detection limits in org a nic-free wa ter samples fortified with pesticides at a concentration of 0.025

μg /L rang ed from 0.0019 to 0.022 μg /L for all compounds in the method. The g r and mean (m ean of m ean recove ries for individual compounds) recoveries in org a nic-free water

sa mple s r a ng e d f

r o m 72 to 89 pe r c e n t, f o r tif ie d with pe stic ide s a t thr e e c onc e n tr a tions be twe e n 0.025 and 0.5 μg /L . Grand mean recoveries in

g r ound- and surface-water samples rang ed from 46 to 119 percent, also fortified with

pest i c i d es at t h ree concent r at i ons bet w een 0.025 and 0.5 μg /L . L ong -term recoveries

f r o m r e a g e n t wa te r spike s we r e use d to demonstrate that 38 of 65 compounds can be reported without qua lification of the

qua ntita tive r e sult a c r oss the a n a l y tic a l r a ng e of the method. The remaining 27 are reported with qua lif ie d e s tima te s of c onc e n tr a tion because of g r eater variability of recovery

.

INTRODUCTION

I n 1996, the National Water Quality

L a boratory (NW Q L ) developed and implemented a g r a phitiz ed carbon-based solid-phase ex traction and hig h -performance liquid chromatog r aphic analy tical method to

de te r mine pe stic ide c onc e n tr a tions in sur f a c e

and g r ound-water samples (W erner and others, 1996). The Na tional W a ter-Quality

Asse ssme n t Pr og r a m ( NAWQA) use s this method for determining concentrations of 41 pola r pe stic ide s a nd pe stic ide me ta bolite s. NAW QA used the methods of W e rner and others (1996) and Z a ug g and others (1995) to develop a detailed and ex te nsive da ta se t f o r nationwide assessment of pesticide presence, concentrations, and distribution (L arson and others, 1999).

I N T R ODUCT I O N 1

### The method by W e rner and others (1996) initially was develope d because several pesticide classes that mig ht be found in g r oundwat e r and surface-wat e r sam p l e s are not readi l y

am enabl e t o anal y s i s by g a s chrom a t o g r aphy (GC) or g a s chromatog r aphy /mass

spe c t r o me tr y

( G C/MS)

. Ana l y s is by GC/MS is a long -established method for unequivocal

ide n tif ic a tion a nd qua ntita tion of or g a nic compounds, but these compound classes could not be analy z ed without derivitiz ation or other sample-modify ing steps. Ex amples of these

pe stic ide c l a sse s inc l ude pheny lurea herbicides, chlorophenox y acetic acid herbicides,

me thy l c a r ba ma te inse c tic ide s , sulf ony lur e a
, sulfonamide, and imidaz olinone herbicides,

and uraci l

- deri vat i v e pest i c i d es. Because t h ese pest i c i d es are used on a nat i onal scal e i n l a rg e

qua ntitie s, a br oa d- spe c t r u m, se nsitive analy tical method for monitoring selected

pest i c i d es i n t h ese cl asses was needed. The

method of W e rner and others (1996) initially

f u lf ille d this r e quir e me nt, but in r outine use
, shor tc oming s we r e ide n tif ied that were inherent to the available analy ti cal technolog ies used in the method. Several impor tant polar pesticides could not be adequately r e solve d a nd ide n tif ie d by hig h -performance liquid chromatog r aphy (HPL C) with photodiode-a rray detection. I n addition, detection, identification, and

qua ntita tion of pola r pe stic ide s in the pr e s e n c e of co-isolated and ubiquitous dissolved org a nic

m a t t e r requi red a m o re speci fi c m eans of

de te c tion a nd ide n tif ic a tion to r outine l y a c h ie ve the de te c tion limits ne e d e d f

o r

a m bie n t
environmental concentrations.

Concurrent with development of the method by W e rner and others (1996), improvements were made in hig h

performance liquid chromatog r aphy /mass

spect rom e t r y

(HP L C / MS ) i n t e rfaces so t h at

se nsitive a nd se le c tive de te c tion of pola r

pe stic ide s a nd pe stic ide me ta bolite s c a n be

ma de r outine l y in e x tr a c t s f r o m 1- L wa te r samples (F errer and B a rcelo, 1998). These newer atmospheric pr essure ioniz a tion

i n t e rfaces al l o w unat t e nded and nearl y continuous operation of HPL C /MS sy stems,
with de te c tion limits ( e x p r e sse d a s a f

ilte r e dwa te r c onc e n tr a tion in a nomina l 1- L wa te r sample) as low as the tens of nanog rams per liter (Crescenz i and others, 1997).

The use of HP L C / M S as a rout i n e analy tical tool under production conditions

was tested at the NW QL by F u rlong and others (2000) for determination of sulfony lurea, imidazolinone, and sulfonamide herbicides. This study demonstrated that with

suf f i c i e n t la bor a t or y

a nd f i e l d qua lity c ontr o l, hundreds of samples c ould be successfully analy z ed by HPL C /MS, at concentrations in

the na nog r a m- pe r

- lite r r a ng e

. The pr oble m s of anal y t e coel ut i on and i n t e rference from dissolved org a nic carbon are substantially

r e duc e d by c o mbining the instr u me nta l approach of F u rlong and others (2000) with the solid-phase ex traction procedure by

W e rner and others (1996). As noted by

W e rner and others (1996), the advantag es of

HPL C coupled with solid-phase ex traction

over other methods include use of less solvent, rapid ex traction, field-ex traction

c a p a b ilitie s, lowe r solve n t e x posur e to

te c hnic i a n s, a nd the a b ility to a u toma te the

e x tr a c tion pr oc e dur e a nd de te r mine the r ma lly sensitive compounds. Althoug h the addition

of m a ss spect rom e t r y

i n creases t h e anal y t i cal cost, this cost is outweig hed by improvements in spe c i f i c ity a nd de te c t a b ility . Colle c tive l y , sl i g ht l y i n creased anal y t i c al cost s are

outwe ig he d by impr ove me nts in da ta qua lity

.

The method described herein was developed by the U.S. Geolog ical Survey (USGS) for use at the NW QL . I t uses

g r aphitiz ed carbon-ba sed solid-phase

ex traction coupled with HPL C /MS. The method complements the method by W e rner and others (1996) by in creasing the number of compounds identified and quantified from 39

to 65. I t provides s imilar method detection

limits a nd e nha nc e d de te c tion of low

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 2

### concentrations of compounds in sample matrices with hig h dissolved org a nic carbon

concentrations and other ma tr ix inte r f e r e nc e s

. I t also supplements other methods of the USGS for determination of org a nic substances in water that are described by

W e rshaw and others (1987) and by F i shman (1993).

This report provi des a detailed description of all aspects of the method, including equipment, reag ents, sample

ex traction and elution techniques, sampling

pr otoc ol, ta bula t e d qua lity

- c ontr o l da ta

, calculations, and reporting of results. B i as and variability data and method detection

limits f o r

65 pe stic ide s a r e pr e s e n te d.

The scope of the report includes determination of method performance in

or g a nic

- f r e e wa te r sa mple s a nd in two natural-water ty pes— a g r ound-water sample

and a surface-wat e r sam p l e from t h e Denver, Colorado, reg i on. Method performance was

det e rm i n ed at t h ree pest i c i d e concent r ations—0.025, 0.10, and 0.50 μ g /L —in each

wat e r t y pe, wi t h t h e ex cept i on of surface

wat e r, where t h e l o west concent r at i on was 0.05 μg /L . Method detection limits (MDL s) were determined in org a nic-free water at a concentration of 0.025 μg /L by using the method outlined by the U.S. Environmental Protection Ag ency (1997).

The method described in this report was approved in J une 1999 as a custom analy tical method and implemented for routine sample analy s is as provisional l a borat ory anal y t i cal

schedule L C 9060. I t wa s intended primarily

for t h e anal y s i s of sam p l e s associ at ed wi t h t h e NAW QA prog ram. The method has remained in use until the present (2001) with only

minor modifications. AN AL Y T I C AL M E T H O D

Organic Compounds and Parameter

Codes: Pest icides, Dissolv e d, Graphitized Carbon-Based Extraction, High-Performance Liquid

C h romat ography /M ass Spect r omet ry , O- 2060- 01

1. A pplicat ion

This method is suitable for use with

f ilte r e d wa te r sa mple s f o r

the de te r mina tion of the pesticides and rela ted deg r adation products that are specified in table 1. Many parent compounds, such as 2,4-D, were included

because of t h ei r rel a t i v e i m port a nce i n

ag ri cul t u re i n t h e Uni t e d S t at es, as i ndi cat e d by the amount applied nationally (Gianessi and Anderson, 1996). Other compounds, such as aldicarb, have or can have substantial impact on human or ecosy stem health (Gustafson, 1993). Some compounds, such as caffeine, are ubiquitously detected and mig ht

indicate human wastew ater contamination (Guly a s, 1997). Several compounds, such as 2-hy drox y a traz ine, are important deg r adation products of commonly used pesticides (Kolpin and others, 1998). The method is applicable

f o r

de te r mining pe stic ide s a nd pe stic ide

me ta bolite s tha t a r e ( 1 ) e f f i c i e n tly isola t e d

f r o m the sa mple ma tr ix a nd a d sor b e d onto a

g r aphitiz ed carbon black sorbent-filled

c a r tr idg e , a nd ( 2 ) c h r o ma tog r a phic a lly

r e solve d a nd ide n tif ie d using a n HPL C coupled by an electrosp ray ioniz a tion source to a quadrupole mass spectrometer.

The method has been tested and

va lida t e d f

o r

f

ilte r e d sur f a c e wa te r a nd

g r ound water. Althoug h not specifically tested for other aqueous matrices, it could be applied to precipitation, wastewater, tile drain discharg e, and other sa mple ty pes as long as

AN AL Y T I C AL M E T H O D 34 Pesti cides in Water by Gra phitized Carbon-Based SPE and HPLC/MSTable 1.Compound names, uses, pesticide class, Chemical Abstract Service registry numbers, and codes[conc., concentration; Y/N, yes/no; CAS, Chemical Abstract Service; NWIS, National Water Information System; Use codes in alphabetical order; F, Fungicide;H, Herbicide; H-Degr., Herbicide degradant; I, Insecticide; I-Degr., Insecticide degradant. Class codes in alphabetical order:AA, Acylalanine; ACA, Acetamide;B., Biological agent; BI, Benzimidazole; BN, Benzonitrile; BTZ, Benzothiadiazole; BZ, Benzoic acid; C, Carbamate; CN, Chloro-Nicotinyl; CP, ChlorophenoxyAcid; DNA, Dinitroaniline; DNP, Dinitrophenol; DPE, Diphenyl ether; IMI, Imidazolinone; PH, Phthalimide; PU, Phenylurea; PY, Pyridine; PYA,Pyridyloxyacetic acid; PYD, Pyridazine; SA, Sulfonamide; SU, Sulfonylurea; T, Triazine; TC, Thiocarbamate; TDZ, Thiadiazole; TR, Triazole; U, Uracil; n/a,not applicable]CompoundnameAlternative orcommon nameReportedas anestimatedconc.1(Y/N)UseClassCAS registrynumberNWISparametercodeIonizationmode foridentificationandquantitation2,4,5-T (Negative Ion Surrogate)Trichlorophenoxyacetic acidNHCP93-76-599958Negative Ion2,4-DWeedone-2,4-DPNHCP94-75-739732Negative Ion2,4-D methyl ester2,4-Dichlorophenoxyaceticmethyl esterNHCP1928-38-750470Positive Ion2,4-DB4-(2,4-dichlorophenoxy)butanoic acidYHCP94-82-638746Negative Ion2,4-Dichlorophenylacetic acid(DCAA; negative ion internalstandard)n/a19719-28-9Negative Ion2-Hydroxyatrazine4-(ethylamino)-6-[(1-methylethyl)amino]-1,3,5-Triazin-2(1H)-oneYH-Degr.T2163-68-050355Positive Ion3(4-chlorophenyl)-1-methyl ureaN'-(4-chlorophenyl)-NmethylureaNH-Degr.PU5352-88-561692Positive Ion3-Hydroxycarbofuran2,3-dihydro-2,2-dimethyl-3,7-Benzofurandiol, 7-(methylcarbamate)NI-Degr.C16655-82-649308Positive Ion3-Ketocarbofuran3-oxocarbofuranYI-Degr.C16709-30-150295Positive IonAcifluorfenTackle; BlazerNHDPE50594-66-649315Negative IonAldicarbTemikYIC116-06-349312Positive IonAldicarb sulfoneAldoxycarbYI-Degr.C1646-88-449313Positive IonAldicarb sulfoxideTemik SulfoxideYI-Degr.C1646-87-349314Positive IonAtrazineAtrex; AtratolNHT1912-24-939632Positive IonTable 1.Compound names, uses, pesticide class,Chemical AbstractService registrynumbers,and codes—Continued

ANAL Y T I CAL M E T H OD 5CompoundnameAlternative orcommon nameReportedas anestimatedconc.1(Y/N)UseClassCAS registrynumberNWISparametercodeIonizationmodeforidentificationandquantitationBarban(positive ionsurrogate)Carbyne; Neoban;CaryneNHC101-27-990640Positive IonBendiocarbFicamNIC22781-23-350299PositiveIonBenomylBenlateNFBI17804-35-250300Positive IonBensulfuron-methylLondaxNHSU83055-99-661693Positive IonBentazonAdagio;Galaxy;StormYHBTZ25057-89-038711Negative IonBromacilBromax; Hyvar; UragonYHU314-40-904029Positive IonBromoxynilBromanil; Buctril; TorchYHBN1689-84-549311Negative IonCaffeine1,3,7-TrimethylxanthineN58-08-250305Positive IonCaffeine-C13 (positive ionsurrogate)N99959Positive IonCarbarylSevinNHC63-25-249310Positive IonCarbofuranCrisfuran;FuradanNHC1563-66-249309Positive IonChlorambenmethylesterAmiben, methylesterYHCP7286-84-261188Positive IonChlorimuron-ethylClassicNHSU90982-32-450306Positive IonChlorothalonilBravo;ForturfYHPH1897-45-649306Negative IonClopyralidStinger;LontrelNHPY1702-17-649305Negative IonCycloateRo-Neet; MarathonYHTC1134-23-204031Positive IonDacthal monoacidDCPAMonoacid; MonomethyltetrachloroterephtalateNH-Degr.CP887-54-749304NegativeIonDeethylatrazine2-Amino-4-isopropylamino-6-chloro-s-triazineYH-Degr.T6190-65-404040PositiveIonDeethyldeisopropylatrazine6-chloro-1,3,5-triazine-2,4-diamineYH-Degr.T3397-62-404039PositiveIonDeisopropylatrazineAmino-2-chloro-6-ethylamino-striazineYH-Degr.T1007-28-904038PositiveIonDicambaBanval;Marksman;ClarityNHBZ1918-00-938442Negative IonDichlorprop2,4-DP,Weedone DPNHCP120-36-549302Negative IonDinosebDNPB;Caldon:DynamiteNHDNP88-85-749301Negative Ion6 Pesti cides in Water by Gra phitized Carbon-Based SPE and HPLC/MSTable 1.Compound names, uses, pesticide class, Chemical Abstract Service registry numbers, and codes—ContinuedCompoundnameAlternative orcommon nameReportedas anestimatedconc.1(Y/N)UseClassCAS registrynumberNWISparametercodeIonizationmode foridentificationandquantitationDiphenamidDymid; Enide; Rideon; DyfenNHACA957-51-704033Positive IonDiuronDCMU; Diurex; AguronNHPU330-54-149300Positive IonFenuronBeet-KleanNHPU101-42-849297Positive IonFlumetsulamDE 498; XRD 498YHSA98967-40-961694Positive IonFluometuronCortoran; Lanex; CottonexNHPU2164-17-238811Positive IonImazaquinImage 1.5LC; Scepter 1.5LYHIMI81335-37-750356Positive IonImazethapyrPursuit; Pursuit DGYHIMI81335-77-550407Positive IonImidaclopridAdmire; Gaucho; MeritNICN138261-41-361695Positive IonLinuronLorox; Afalon; Linurex; LinexNHPU330-55-238478Positive IonMCPABordermaster; MetaxonNHCP94-74-638482Negative IonMCPBTropotox; Can-Trol; PDQYHCP94-81-538487Negative IonMetalaxylApron; Subdue; RidomilNFAA57837-19-150359Positive IonMethiocarbMercaptodimethur; Draza;MesurolYIC2032-65-738501Positive IonMethomylNudrin; Lannate; LanoxYIC16752-77-549296Positive IonMethomyl oxime1-(methylthio)-acetaldehydeoximeYI-Degr.C13749-94-561696Positive IonMetsulfuron-methylEscort;Gropper; AllyYHSU74223-64-661697Positive IonMonuron (positive ion internalstandard)Telvarn/aHPU150-68-5Positive IonNeburonGranurex; Herbalt; KlobenNHPU555-37-349294Positive IonNicosulfuronAccent; AccentDFNHSU111991-09-450364Positive IonNorflurazonZorial; Evital; Solicam; TelokYHPYD27314-13-249293Positive IonOryzalinRyzelan; Surflan; DirimalNHDNA19044-88-349292Positive IonOxamylVydate: ThioxamylNIC23135-22-038866Positive IonTable 1.Compound names, uses, pesticide class,Chemical AbstractService registrynumbers,and codes—Continued

A N A LYTIC A L METHCompoundnameAlternative orcommon nameReportedas anestimatedconc.1(Y/N)UseClassCAS registrynumberNWISparametercodeIonizationmodeforidentificationandquantitationOxamyloxime2-(Hydroxyimino)-N,N-dimethyl2-(methylmercapto)acetamideYI-Degr.C30558-43-150410PositiveIonPicloramTordon;Amdon;GrazonNHPY1918-02-149291Negative IonProphamIPC;Chem-Hoe; PremaloxNHC122-42-949236Positive IonPropiconazoleTilt; Orbit; Banner: Proconazole;WocosinNFTR60207-90-150471PositiveIonPropoxurBaygon; PHC;Suncide; UndenNIC114-26-138538Positive IonSiduronTupersan; TreyNHPH1982-49-638548Positive IonSulfometuron-methylOust; DPX-T5648NHSU74222-97-250337Positive IonTebuthiuronGraslan;Spike; PerflanNHTDZ34014-18-182670Positive IonTerbacilSinbar; DPX-D732; GeonterYHU5902-51-204032Positive IonTribenuron-methylExpress; tribenuronmethylester;DPX-L5300YHSU101200-48-061159PositiveIonTriclopyrGarlon; Curtail; Redeem;RemedyNHPYA55335-06-349235NegativeIon1The term"estimated concentration"isusedinthis electronic file. It was changedfrom"qualifiedestimate,"whichwas usedinthe original publishedreport.Tables13–24 and tables26–31 alsoreflectthischange. (Modified:February4, 2002, etf)

OD 7

### ( 1 ) the sa mple s ha ve be e n f ilte r e d using the method of Shelton (1994), and (2) the user

recog n i z es t h at perform ance charact eri s t i c s of

new m a t r i ces are not t e st ed and any resul t s would be provisional.

Two classes of de te r mina tions a r e reported for samples analy z ed by this method. Compounds for which the results of the

determination are reported without qualification make up the first class. Compounds for which the results of the

de te r mina tion a r e r e ported as qualified

e s tima te s, a nd the c onc e n tr a tion qua lif ie d with an “E”, are in the second class. The classification for each compound in the

method is listed in table 1.

These cl asses, and t h e cri t e ri a used t o

e s ta blish the m , a r e disc usse d in de ta il in section 11.6. Compounds that are reported without qualification are reproduciblywellrecovered using this method, as defined by

median recoveries of long -term laboratory

reag ent spikes (L RS) between 60 and 120 percent and with variation (as indicated by the nonparametric st atistic F

- pseudosig ma) less than ± 25 percent. Compounds that are

r e por te d a s qua lif ie d e s tima te s do not me e t these long -term method performance criteria, but are retained in the method because they

a r e use d in substa ntia l qua ntity a nd ha ve important environmental or tox i colog i cal effects. Althoug h quantitative method perform ance for t h i s cl ass l i e s out si de t h e criteria described above, the criteria for

qua lita tive ide n tif ic a tion of the de te c t e d compounds are the same as that used for compounds reported without quantitative

qua lif ic a tions. Gr e a t e r c e r ta inty e x ists in the

qua ntita tive de te r mina tion of c onc e n tr a tion for compounds reported without qualification—this is the only difference between the reported c oncentrations of the

two data classes. I t is important to note, however, that the

l ong -t erm perform ance cri t e ri a for t h e compounds in the method span a continuum of performance, rather than corresponding to

cat eg ori e s. As a consequence, t h e cri t e ri a

use d to disc r imina t e be twe e n the two c l a sse s of data, althoug h cons istent with common

anal y t i cal pract i ce, are i nherent l y arbi t r ary

. The qua lita tive ide n tif ic a tion of the compounds in both classes is equally reliable. Thus, data users should consider the estimated

concent r at i on as a cat eg ori cal warni n g t o pay

ex tra attention to potential use of numerical concentrations, but not as a distinct boundary between g ood and poor data.

2. Summary of Method

This method is desig n ed for the determination of 65 pes tic ide s a nd pe stic ide deg r adation products and caffeine (table 1) in

filtered natural-water sa mples. The method is

a

pplic a b le to pe stic ide s tha t a r e ( 1 ) e f f i c i e n tly

pa r titione d f r o m the wa te r onto a g r a phitize d carbon-based solid-phase ex traction (SPE)

ma te r i a l , ( 2 ) c a n be qua ntita tive l y e l ute d f

r o m

t h e S P E m a t e ri al , and (3) can be effi ci ent l y ioniz e d by HPL C /MS with electrospray

i n t e rface.

Pe stic ide s a r e e x tr a c t e d f

r o m pr e f ilte r e d water samples by using disposable poly p ropy lene sy ring e cartridg e s that contain 0.5 g of a g r aphitiz ed carbon sorbent. A

pr e f ilte r e d wa te r sa mple of 1 L is pumpe d throug h the SPE cartridg e at a flow rate of 20

mL /min. After ex traction, the adsorbed compounds are eluted from the SPE cartridg e using two sequential elutions of

(1) 1.5 mL methanol, followed by

(2) 13 mL of an 80-percent methy l ene chloride and 20-percent methanol

m i x t u re t h at has been aci di fi ed wi t h trifluoroacetic acid anhy dride (0.2

percent )

.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 8

### The two fractions are reduced under nitrog en to near dry n ess and then combined.

The final volume for the ex tract is 1,000 μL

. Anal y t es are chrom a t o g r aphi cal l y separat e d by HPL C using a reverse-phase

oc ta de c y lsila ne HPL C c o lumn, whic h is coupled to an electrosp ray ioniz a tion interface and quadrupole mass spectrometer for detection, identifica tion, and quantitation.

Each ex t r act i s anal y z ed t w i ce usi n g separat e ioniz a tion modes. The first analy s is is for those compounds that preferentially form positive ions under electrospray conditions, and the second is for those compounds that preferentially form neg a tive ions.

The terms " e x t raction" and " e lution" are used to define specific actions during sample processing . Ex traction is the transfer of the selected compounds from the sample onto the SPE cartridg e . Elution is the removal of the selected compounds from the SPE cartridg e

.

3. Int e rf erences

I n terferences mig ht be caused by compounds recovered fro m a sample matrix

that contains one or more of the same ions as the selected compound and that cannot be

c h r o ma tog r a phic a lly r e solve d f

r o m the selected compounds. Compared to optical detection methods ty pically used with HPL C

,

ma ss spe c t r o me tr y

is le ss a f f e c t e d by

inte r f e r e nc e s , but the pote n tia l f o r i n t e rferences rem a i n s and requi res speci al

a tte ntion to the r a tios of the c h a r a c t e r istic ions

of

inte r e st to a void f a lse positive de te c tions.

I n addition, for the sulfony lurea and

imidaz olinone compound classes, sample

matrix components have been shown

em pi ri cal l y t o resul t i n an apparent i n crease i n compound concentration (F urlong and others, 2000). 4. A pparatus and Instrumentation

N O TE: During the development and implementation of th is method, HewlettPackard Corporation, th e manufacturer of the

HPL C /MS instr u me nta tion use d in de te r mining method performance, form ed a new company

, Ag ilent Technolog ies, from the orig inal

Hewl et t

- P ackard C h em i cal Anal y s i s Di vi si on and other company components. The

HPL C /MS sy stems used in this study were

or ig ina lly ma de by He wl et t

- P ackard, and aft e r formation of the new company

, by Ag ilent Technolog ies. The phrase “HewlettPackard/Ag ilent Technolog ie s” is used in this report to describe this id entical instrumentation.

4.1 High-performance liquid chromatograph —Hewl e t t

- P ackard Model

1090M Series I I or Hewl ett-Packard/Ag ilent Technolog ies Model 1100 hig h -performance liquid chromatog r aphic sy stem equipped as follows: a binary (Model 1100) or direct-ratio (DR5; Model 1090M) ternary

- solvent delivery sy stem, a photodiode-array

ultr a v iole t- a b sor b a n c e de te c t or ( optiona l) , a 250-μL automatic sy ring e sampler, a 100- position random-access au tosampler equipped with a cooling module, and thermostated

c o lumn he a ting

. An I B M- c o mpa tible computer workstation also is required, with a

minimum c onf ig ur a tion of a n I n te l Pe ntium I I Processor operating at a minimum of 266

MHz

, 96 meg a by tes of Random Access Memory , and a minimum 20-g i g a by te hard

disk. Hewlett-Packar d/Ag ilent Technolog ies

L C /MSD ChemStation Revision A.06.03

soft ware, and Thru-P ut S y st em s Targ et Version 3.4 Software, or equivalent, are also required.

4.2 Mass spectrometer— HewlettPackard/Ag ilent Technolog ies Series 1100

L C /MSD ma ss spe c t r o me te r, or equivalent, equipped with an electrospray ioniz a tion

sour c e a nd c a p a b le of ope r a ting in positive and neg a tive ioniz a tion mode.

AN AL Y T I C AL M E T H O D 9

### 4.3 Analytical columns— Chromatographic columns, MetaChem Technolog ies, I n c. I n ertsil octadecy lsilane
(ODS -3), 5  m; 2.1-mm inside diameter by

15-cm st ai nl ess-st eel col u mn or equivalent. A

g u ard column (MetaChem Technolog ies, I n c., MetaGuard 2.0-mm I n erts il octadecy lsilane
(ODS-3) direct-connect, 3  m, or equivalent, also is required.

4.4 Manual sample ex traction

apparatus

4.4.1. Solid-phase extraction manifold —Supelco, I n c., Visiprep SolidPhase Ex traction Vacuum Manifold or equivalent.

4.4.2 C e rami c-pi st on val vel ess sample pumps —Capable of pumping 0 to

25 mL /min, F l uid Metering I n c. Model QSY2 CKC or equivalent.

4.4.3 Sample flow path —All Teflon-perfluoralkox y (PF A ) 1/8-inch tubing (3.18 mm) or equivalent.

4.4.4 Tefz el-tetrafluoroethy l ene
L u er connectors or equivalent.

4.4.5 Luer stopcock—flow control on-off valves —B urdick & J ackson

I n ert PTF E flow-control valves or equivalent.

4.4.6 Vacuum pump —Must be able to draw a vacuum equivalent to at least

102 kPa.

4.5 Automated sample ex traction

apparatus

4.5.1 Zymark AutoTrace 6-place

SPE workstation or equivalent —Equipped for processing 6-mL SPE tubes. 4.5.2 Laboratory-auto trace barrel adapters —Made from 6-mL poly p ropy lene sy ring e tube s ( s tr uc tur a lly identical to the SPE cartridg e without the SPE

pa c k ing ) , c u t to one

- h a l f the or ig ina l le ng th (various manufacturers).

4.5.3 SPE cartridge connectors

— Poly ethy lene (Restek #26007 or equivalent).

4.5.4 Evaporative concentrator

— Tem p erat ure cont rol l e d to 34°C and nitrog en

g a s pressure of 69 kPa Z y mark Turbo-Vap or equivalent.

4.6 L i quid-handling apparatus

4.6.1 Syringes —Ha milton Gastig ht 1750RN, 500 μL (cat. no. 81131); Gastig ht 1001L TN, 1,000 μL (cat. no. 81317); and Hamilton Microliter 701, 10 μL (cat. no. 80366) or equivalent.

4.6.2 Micropipets —Van W a ters and Rog e rs (VW R ) 10- to 100-μL variable volume dig ital microdispenser (cat. no. 53506201), VW R 100-μL fix e d-volume microdispenser (cat. no. 53506675), and

VW R 100-μ L replacement tubes (cat. no. 53508499) or equivalent.

4.6.3 Autosample r v i als

— Na tiona l Sc ie ntif ic Compa n y , 2- mL

, g r aduated amber g l ass fo r use with screw-top caps (cat. no. C4000-2W ) or equivalent.

4.6.4 Vial caps and septa

— Na tiona l Sc ie ntif ic Compa n y , sc r e w- top c a ps with 11-mm dual Teflon -faced silicone septa (cat. no. C4000-53B ) or equivalent.

4.6.5 20-mL solution storage

vi al s— Eag l e-Picher Technolog ies, L L C

, 20 mL , amber with Teflon-faced silicone rubber-lined screw caps (cat. no. 139-20A/CT) or equivalent.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 10

### 4.7 Consumables

4.7.1 Ambe r- glass bottle s

— 1,000 mL , baked at 450°C for 2 hours, fitted

with Te f l on- line d sc r e w caps or equivalent.

4.7.2 Solid-phase extraction cartridges —Supelco ENVI RO-Carb Graphitiz ed Carbon B l ack, g r aphitiz ed nonporous carbon, 500 mg , 120/400 mesh, in

6-mL sy ring e barre l or equivalent.

4.7.3 Nitrogen gas for sam p l e

ex tract concentration, ultrapure.

4.7.4 Test tubes , g r aduated 14-

mL poly p ropy lene round-bottom, 17- by 100-

mm sty l e or equivalent.

4.7.5 Disposable Pasteur pipets
cleaned by ashing at 440 C for 2 hours.

5. R eagent s and Solut i ons

N O TE: Ma te r i a l Sa f e ty Da ta She e t s f o r

a ll

materials described here in need to be read

pr ior to using a n y of the s e ma te r i a l s to e n sur e safe handling and prope r disposal. Unless otherwise specified, solutions should be stored at room temperature and should be used for no long er than 6 months.

5.1 Neat reag ents

5.1.1 Ac e t onitrile —B urdick and

J ackson, ultraviolet (UV) g r ade or equivalent.

5.1.2 L

– (+ )– A s c o r b i c a c i d —J .T.

B a ker, reag ent g r ade or equivalent.

5.1.3 Formic ac id solution —88

pe r c e n t, Ma llinc kr o f t AR or e quiva le nt.

5.1.4 Liquinox, liquid detergent —Alconox I n c. or equivalent.

5.1.5 Methanol —B urdick and

J ackson, HPL C g r ade or equivalent. 5.1.6 Met h yl ene chl o ri de

— B u rdick and J ackson, pesticide g r ade or equivalent.

5.1.7 Trifluoroacetic acid anhydride ( T

FA) —P i e rce C h em i cal , I n c.,

reag ent g r ade or equivalent.

5.1.8 W a ter, organic

- f

r ee— De ionize d a nd distille d wa te r tha t is f r e e f r o m interfering org a nic compounds and chlorine.

5.1.9 Ammonium acetate— J. T

. B a ker, reag ent g r ade or equivalent.

5.1.10 Sodium chloride —EM Science, reag ent g r ade or equivalent.

5.1.11 Sodium hydroxide

pe lle ts —Reag ent g r ade or equivalent.

5.1.12 Isopropyl alcohol

— B u rdick and J ackson, HPL C g r ade or equivalent.

5.2 Solutions

5.2.1 SPE cartridg e conditioning

solutions

5.2.1.1 Solution 1 —80-percent

me thy l e n e c h lor i de /20- pe r c e n t me tha nol. Mix

400 mL of methy l ene chloride with 100 mL

of

me tha nol. Stor e in a c a libr a te d a d justa b le

di spenser. R e pl ace sol u t i on at l east weekl y

.

5.2.1.2 Solution 2 —Ascorbic acid solution. Dissolve 10 g of ascorbic acid (5.1.2) in 1 L org a nic -free water and mix

. Refrig e rate at 4°C and replace solution at

l east weekl y

.

5.2.2 SPE cartridge elution

solution —80-percent methy l ene chloride/20- percent methanol/0.2-pe rcent trifluoroacetic acid anhy dride (TF A ). Mix 400 mL of methy l ene chloride, 100 mL methanol, and

AN AL Y T I C AL M E T H O D 1 1

### 1,000 μL of TF A (5.1.7). Prepare solution

dai l y and st ore i t i n Aut o Trace reservoi r.

5.2.3 Eluent neutralization

solution —10 percent w/v sodium hy drox ide

solution. W e ig h 10 g of sodium hy drox ide pellets (5.1.11). Dissolve sodium hy drox ide pellets in 100 mL org a nic-free water and mix

.

5.2.4 AutoTrace workstation cleaning solution ( Liquinox detergent solution) —Dilute four drops of L i quinox (5.1.4) with 4 L of org a nic-free water and

mix

.

5.2.5 C oncent r at ed ammonium acetate in organic-free water solution

— W e ig h 20 g ammonium acetate (cry stalline) (5.1.9) into a 1-L flask. Dissolve the

am m oni um acet at e wi t h org a ni c-free wat e r (5.1.8) and dilute to volume in the flask.

F ilter the solution throug h a 47-mm, 0.2-μm

ny lon f ilte r me mbr a ne into a c l e a n, bur ne d

f ilte r f

l a s k. Tr a n sf e r

solution into a c l e a n a nd

bur ne d 1- L bottle . The f i na l c onc e n tr a tion is 20 g / L (0.26 molar). Store at room

t e m p erat ure.

5.2.6 Concentrated ammonium

acetate in methanol and acetonitrile

solution —W ei g h 20 g am m oni um acet at e (cry stalline) (5.1.9) into a tared 1-L flask.

Di ssol v e t h e am m oni um acet at e i n t h e fl ask

with 500 mL of methanol, then add 500 mL

of acet oni t r i l e . Do not prem i x t h e m e t h anol

and acet oni t r i l e because am m oni um acet at e does not dissolve easily in the presence of

acet oni t r i l e . Use a st i rri ng m a g n et and m i x er with no heat to fully dissolve all ammonium

acet at e. Once i t i s di ssol v ed, t h e am m oni um acetate will stay in solution. The final concentration is 20 g / L (0.26 molar). Store at

room temperature. 5.3 HPL C mobile phase preparation

N O TE: The concentrations of formic acid inthe mobile phase are varied from instrumentto- i nstr ume n t a nd c o lumn- t o- c o lumn to optimiz e chromatog r aphic separation. The

fol l o wi ng concent r at i ons are for reference.

5.3.1 Organic solvent eluent ( a c e t onitrile modifie d with ammonium ac e t ate solution)

— Use a 7-mL class A pipet to

m easure 7 m L of t h e am m oni um acet at e i n acetonitrile:methanol solution (5.2.6), and

transfer to a 500-mL volumetric flask. Dilute

the solution in the flask to 500 mL with

HP L C -g rade acetonitrile (5.1.1) and mix

. F ilte r the solution thr oug h a 47-mm, 0.2-μm

ny lon f ilte r me mbr a ne into a c l e a n, bur ne d

f ilte r f

l a s k. Tr a n sf e r

to HPL C e l ue nt r e se r voir

B for use. The final concentration is 0.28 g / L (3.63 millimolar).

5.3.2 Aqueous eluent ( organicfre e wate r modifie d with ammonium ac e t ate solution and formic acid)

— Use a 7-m L cl ass A pipet to measure 14 mL (in two aliquots) of

t h e am m oni um acet at e i n org a ni c-free wat e r solution (5.2.5), and place in a 1-L volumetric flask. Use a g r aduated cy linder to add 40 mL

of acet oni t r i l e t o t h e 1-L vol um et ri c fl ask. Use a 500-μL sy ring e to add 200 μL of formic acid (5.1.3) to the solution in the flask.

Dilute the solution in the f l a s k to 1 L with

org a nic-free water (5.1.8) and mix . F ilter the solution throug h a 47-mm, 0.2-μm ny lon filter

me mbr a ne into a c l e a n, bur ne d f ilte r f

l a s k.

Transfer to HPL C eluent reservoi r A for use.

The fi nal concent r at i on of ammonium acetate in the solution is 0.28 g / L (3.63 millimolar).

The final concentration of formic acid in the solution is 0.24 g / L (5.22 millimolar).

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 12

### 5.4 Calibration and quality -control

standard solutions

I n this method, each sample is analy z ed

t w i ce, once for pest i c i d es t h at preferent i a l l y form neg a tive ions and once for pesticides

tha t pr e f e r e n tia lly f

o r

m positive ions. Althoug h the chromatog r aphic conditions are identical for both analy s es, it is important that

the stock solutions used for calibration and

qua lity

- c ontr o l sta nda r d s be pr e p a r e d separately rather than in combination. There

is a substa ntia l possibility tha t inte r f e r e nc e s from co-eluting compounds or crossreactivity among compounds will affect the identification and qua ntitation of method

anal y t es i f sol u t i ons are com b i n ed. Thi s probl em al so m i g ht be ex acerbat e d by t h e hig h concentrations of the stock solutions.

All c a libr a tion a nd qua lity c ontr o l ( Q C)

standard solutions are derived from three

c o mmon mix e d sta nda r d s, mix e d f

r o m the hig h -concentration, sing le-component solutions (see 5.4.1 and 5.4.2 below). These

solutions a r e r e f e r

r e d to a s positive mix 1, positive mix 2, a nd ne g a tive mix . The pur pose of using these solutions for all subsequent calibration and QC standard solutions is to

r e duc e pote n tia l disc r e pa nc ie s in inte r p r e ting QC results.

The overal l approach i s t o prepare t h ree 20,000- μ g / L multicomponent solutions that

tog e ther include all compounds in the method

ex cept for surrog a t e s and i n t e rnal st andards.

F r om these solutions, working standards are

ma de tha t c onta i n the a ppr opr ia te positive a nd

neg a tive surrog a te compounds. The

c a libr a tion solutions a r e the n de r i ve d f r o m the

worki n g st andards. The speci fi cat i ons for t h e solutions are contained in the following

sections and should be used if an ex ternal (commercial) source of standard solutions is

used for this method. I ndividual sing lecomponent stock solutions (at about 1 to 10

m g / m L ) are prepared from neat m a t e ri al or purchased at a known purity from a

commercial source. Af ter formulation, all solutions, e x c e p t the c a libr a tion sta nda r d s

m a de pri o r t o anal y s i s , are st ored i n a freez er in labeled, amber 20-mL g l ass vials with Teflon-faced, silicone rubber-lined screw

caps.

5.4.1 Calibration solutions for compounds determined under negative

ionization conditions —F or compound

mix tures determined under neg a tive

ioniz a tion conditions, sing le compound stock solutions and multicomponent stock and

cal i b rat i on sol u t i ons are prepared wi t h HP L C

g r ade methanol (5.1.5). Prepare individual stock solutions of 10 mg /mL by dissolving 50

mg of the se le c t e d pe stic ide s in a 5- mL amber-g lass volumetric flask and dilute to

vol um e usi n g m e t h anol t o di ssol v e each compound. F o r neg a tive ioniz a tion analy s is, prepare a multicomponent stock solution for each listed compound by calculating the aliquot of each individual stock solution

necessary to produce a final concentration of 20.0 ng /μL

, calculated as follows:



##  

   



ss f

ss 

## C V C V f (1)

w h ere V ss 

### = the stock solution v o lum e used, in m i croliters,

ty

pically  200 μ L;

C

f 

### = the final solution concentration (for this solution 20.0

ng /μL ≡ 20,000 μ g/ L ) ;

V

f 

### = the final solution v o lum e (for this solution, 100 m L

100,000 μL); and

C

ss 

### = the stocksolution concentration (for this solution, 10

m g / m L 10,000 ng /  L)

. 

### Use a variable-volume microdispenser (see 4.6.2) to add the calculated aliquot of each compound to a 100-mL amber-g lass volumetric flask. Dilute the combined compounds to volume with methanol. Prepare a new primary fortified standard solution every 6 months.

AN AL Y T I C AL M E T H O D 1 3

### Stor e a ll solutions in a r e f r i g e r a tor in c l e a n e d

a nd bur ne d a m be r g l a ss via l s or bottle s with Teflon-lined screw caps. F o r all compounds

e x c e p t tr ic lopy r a nd c h lor o tha l onil, sing le component stock solutions are usable for no

more than 12 months. F o r triclopy r and chlorothalonil, sing le component stock

solutions are usable for no more than 3 months. The components of the neg a tive ion

solution a r e liste d in ta ble 2.

5.4.2 Preparation of multicomponent standard solutions for compounds determined under positive

ionization conditions —Calibration, calibration verification, lab reag ent spike fortification, and field matrix spike

f o r tif ic a tion solutions a r e pr e p a r e d by diluting
hig h -concentration (20,000  g/ L )

, multicomponent standard solutions. These solutions are prepared from individual compound stock solutions, made up in one or

m o re sol v ent s , and are l i s t e d for each si ng l e compound in table 3. Prepare individual stock solutions of 10 mg /mL by dissolving 50

mg of the se le c t e d pe stic ide s in a 5- mL amber-g lass volumetric flask and dilute to volume by using methanol or appropriate solvent to dissolve the compound (listed in table 3).

Two multicomponent calibration solutions are prepared for compounds determined under positive ionization

conditions. The first solution contains all the positive ioniz a tion compounds ex cept for deethy ldeisopropy latraz ine and 2-hy drox y

atraz i ne. The second solution contains only deethy ldeisopropy latraz ine and 2-hy drox y

atraz i ne. Two separate sol u t i ons are prepared

because deet hy l d ei sopropy l a t r az i n e and 2- hy drox y a traz ine require acid to dissolve the compounds in the stock solutions, and, if combined into the primary solution, would have potential for de g r adation of other compounds in the primary solution. There

a l so is pote n tia l f o r

c r oss- r e a c tivity with othe r compounds in the primary mix ed standard

solution. F o r positive ioniz a tion analy s is, prepare two multicomponent stock solutions by calculating the aliquot of each individual stock solution necessary to produce a final concentration of 20.0 ng /μL

, calculated as indicated in equation (1 ) and repeated below:

Ta b l e 2 Calibr a tion s o lution c o m pos ition f o r c o m pounds deter m i ned under negative ioniz a tion c onditions

[C A S , C h em ical A b s t ract Serv ices ]

Compound na me CA S numbe r St o ck so lu t i o n

so lv en t
2,4- D 9 4

- 75- 7 Met h an ol
2,4- D B 9 4

- 82- 6 Met h an ol

A c i f l u orf e n 5 0 5 9 4

- 66- 6 Met h an ol

Ben t azon 2 5 0 5 7

- 89- 0 Met h an ol

Brom ox y n i l 1 6 8 9

- 84- 5 Met h an ol

C h l o rot h al on i l 1 8 9 7

- 45- 6 Met h an ol

C l opy ral i d 1 7 0 2

- 17- 6 Met h an ol

D act h a l m o n o aci d (Mon om et h y l t e t r ach l o rot e reph t h al at e) 887- 54- 7 Met h an ol

D i cam b a 1 9 1 8

- 00- 9 Met h an ol

D i ch l o p r o p 1 2 0

- 36- 5 Met h an ol

D i n o s e b 8 8

- 85- 7 Met h an ol

MC PA (4- C h l oro- o

- t ol y l ox y acet i c aci d) 94- 74- 6 Met h an ol

MC P B 9 4

- 81- 5 Met h an ol

Pi cl oram 1 9 1 8

- 02- 1 Met h an ol

T r i c l opy r 5 5 3 3 5

- 06- 3 Met h an ol

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 14Ta b l e 3 Calibr a tion s o lution c o m pos ition f o r c o m pounds deter m i ned under pos itive ioniz a tion c onditions

[C A S , C h em ical A b s t ract Serv ices ; %, percen t]

Compound na me CA S numbe r S t oc k s o lution s o lv e n t

Pos i tive S o lu tion M i x t u re 1 2,4- D m e t h y l es t e r 1928- 38- 7 Met h an ol 3(4- ch l o roph en y l )- 1- m e t h y l u r ea 1897- 46- 6 Met h an ol

3- H y drox y carbof u r an 1 6 6 5 5

- 82- 6 Met h an ol

3- K e t o carbof u r an 1 6 7 0 9

- 30- 1 A cet on e A l di c a r b 1 1 6

- 06- 3 Met h an ol

A l di carb s u l f on e 1646- 88- 4 Met h an ol

A l di carb s u l f ox i d e 1646- 87- 3 A cet on i t r i l e A t razi n e 1 9 1 2

- 24- 9 Met h an ol

Ben d i o c a r b 2 2 7 8 1

- 23- 3 Met h an ol

Ben o m y l 1 7 8 0 4

- 35- 2 A cet on e/ Met h an ol (75: 2 5 )

Ben s u l f u ron

- m e t h y l 8 3 0 5 5

- 99- 6 D i ch l o rom e t h an e Brom aci l 3 1 4

- 40- 9 Met h an ol

C a f f e i n e 5 8

- 08- 2 Met h an ol

C a rbary l 6 3

- 25- 2 Met h an ol

C a rbof u r an 1 5 6 3

- 66- 2 Met h an ol

C h l o ram b en m e t h y l es t e r 7286- 84- 2 Met h an ol

C h l o ri m u ron

- et h y l 9 0 9 8 2

- 32- 4 A cet on i t r i l e C y cl oat e 1 1 3 4

- 23- 2 Met h an ol

D eet h y l a t r azi n e 6 1 9 0

- 65- 4 Met h an ol

D e i s opropy l a t r azi n e 1 0 0 7

- 28- 9 D i ch l o rom e t h an e
D i ph en am i d 9 5 7

- 51- 7 Met h an ol

D i u r on 3 3 0

- 54- 1 Met h an ol

F e n u r on 1 0 1

- 42- 8 Met h an ol

F l u m et s u l a m 9 8 9 6 7

- 40- 9 Met h an ol / A cet on e (50: 5 0 )

F l u o m e t u ron 2 1 6 4

- 17- 2 Met h an ol

Im azaqu i n 8 1 3 3 5

- 37- 7 Dich lorom e th an e/Meth an o l ( 6 0 : 4 0 )

Im azeth a py r (P u r s u it) 81335- 77- 5 A ceton e
Im i d acl opri d 1 3 8 2 6 1

- 41- 3 Met h an ol

L i n u r on 3 3 0

- 55- 2 Met h an ol

Met a l a x y l 5 7 8 3 7

- 19- 1 Met h an ol

Met h i o c a r b 2 0 3 2

- 65- 7 Met h an ol

Met h om y l 1 6 7 5 2

- 77- 5 Met h an ol

Met h om y l ox i m e 13749- 94- 5 Met h an ol

Met s u l f u ron

- m e t h y l 7 4 2 2 3

- 64- 6 Met h an ol

N e bu ron 5 5 5

- 37- 3 Met h an ol

Nicos u lf u r on (A ccen t) 111991- 09- 4 A cet on itrile/Meth a n o l/A ceton e (50:25:25)

N o rf l u razon 2 7 3 1 4

- 13- 2 Met h an ol

O r y zal i n 1 9 0 4 4

- 88- 3 Met h an ol

O x am y l 2 3 1 3 5

- 22- 0 Met h an ol

O x am y l ox i m e 30558- 43- 1 D i ch l o rom e t h an e/ Met h an ol (60: 40) Proph am 1 2 2

- 42- 9 Met h an ol

P r opicon azole (T ilt) 60207- 90- 1 Meth an ol Propox u r (Bay g o n ) 114- 26- 1 Met h an ol

S i du ron 1 9 8 2

- 49- 6 Met h an ol

S u l f om et u r on

- m et h y l 7 4 2 2 2

- 97- 2 A cet on i t r i l e / D i c h l orom et h a n e (50: 5 0 )

T e bu t h i u ron 3 4 0 1 4

- 18- 1 A cet on e
T e rbaci l 5 9 0 2

- 51- 2 Met h an ol

T r i b en u r on

- m et h y l 1 0 1 2 0 0

- 48- 0 A cet on i t r i l e
Pos i ti ve S o l u ti on M i x t u re 2

2- H y drox y a t r azi n e 2163- 68- 0 Met h an ol / A cet on e / H y droch l ori c A c i d (aq) [36% ] (49.9: 49.9: 0.2)

D eet h y l d ei s opropy l a t r azi n e 3397- 62- 4 Met h an ol / A cet on e / H y droch l ori c A c i d (aq) [36% ] (49.9: 49.9: 0.2)

AN AL Y T I C AL M E T H O D 1 5

##  

   



ss f f ss 

## C V C V ( 2 )

w h ere V ss 

### = the stock solution v o lum e used, in m i croliters,

ty

pically  200 μ L;

C f 

### = the final solution concentration (for this solution, 20.0 ng /μL);

V f 

### = the final solution

v o lum e (for this solution, 100 m L

100,000 μL); and

C
ss 

### = the stock solution concentration (for this solution, 10 m g /m L

10,000 ng /  L)

.



### Prepare each positive and

neg a tive multicomponent standard solution separately by using a variable-volume microdispenser (4.6.2) to add the calculated aliquot of each compound to a 100-mL amber-g lass volumetric f l a s k. Dilute the combined compounds to volume with methanol. Prepare ne w pr ima r y

f

o r tif ie d

st andard sol u t i on for each m i x t u re every 6

months. Store the solutions in a cleaned and

bur ne d a m be r

- g la ss bottle with Te f l on- line d screw caps. F o r all compounds ex cept 3- hy drox y

- carbofuran, sing le component

stock solutions are usable for no more than

12 months. F o r 3-hy drox y carbofuran, sing le component stock solutions are usable for no more than 3 months. The components of the two multicomponent positive solutions and

the a ppr opr ia te solve n ts f o r

the sing le c o mponent stock solutions are listed in table 3.

5.4.3 Surrogate solution —A sing le surrog a te solution is used for both

ioniz a tion modes. The surrog a tes used for

each anal y s i s are l i s t e d i n t a bl e 4. I ndi vi dual surrog a te stock solutions are made up in

HPL C -g rade methanol to a concentration of 10 mg /mL . The multicomponent surrog a te solution is made up in HPL C -g rade

methanol at a final concentration of 20

ng /  L of each listed compound. All

solutions are transferred to and stored in a

c l e a n e d a nd bur ne d a m be r

- g la ss bottle with Teflon-lined screw caps. Stock solutions for the individual surrog a te compounds are

usable for no more than 12 months.

5.4.4 Laboratory reagent spike fortification and field matrix spike fortific ation solutions —The same solutions

are used for l a borat ory reag ent and m a t r i x spi k es. P r epare t h ree separat e l a borat ory

r e a g e n t spike f o r tif ic a tion solutions ( e x c luding positive a nd ne g a tive ioniza tion

surrog a tes) at a final concentration of 2.5

ng / μ L each. These sol u t i ons are prepared

with a 100-mL volumetric flask, with

me tha nol a s the dilution solve n t. The aliquot of each individual compound to be

use d is c a l c u la te d a s f o llows:



##    



ss t

ss 

## C V C V t (3)

w h ere V ss 

### = the aliquot v o lum e required,

in m i croliters;

C

t 

### = the targ et concentration (in this solution, 2.5 ng /μL);

V

t 

### = the v o lum e of targ et solution required, in m illiliters (100 m L for this solution); and

C

ss 

### = the com pound standard
solution concentration, in

m illig ram / m illiliter (1,000 ng /μL for this solution).

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 16T a b l e 4. Sur r ogate s o lution c o m pos ition f o r c o m pounds deter m i ned under pos itive and negative

ioniz a tion c onditions

[C A S , C h em ical A b s t ract Serv ices ; %, percen t]

Compound na me CA S numbe r S t oc k s o lution s o lv e n t
2,4,5- T (n eg at i v e i o n i zat i o n an al y s i s s u rrog a t e ) 93- 76- 5 Met h an ol

B a rban (pos itiv e ion i zation an aly s is s u rrog a te) 101- 27- 9 Meth an ol

13 C-Ca ffe i n e ( C a ffe i n e ( 2

- 13 C

, 99% : 1 ,3- 15 N 2 ,9 8 % +); p o s itiv e io n i zatio n an aly s is su rro g a te) M e t h an o l



### Use a vari abl e -vol um e m i c rodispenser (see 4.6.2) to add each compound to

the volumetric flask. B r ing the final solution

to volume with methanol. Make three solutions, two for compounds determined under positive ioniz a tion conditions and one for compounds determined under neg a tive

ioniz a tion conditions (5.4.1). Addition of 100

 L of each of these solutions to 1.000 L of

or g a nic

- f r e e wa te r will r e sult in a

concentration of 0.25  g / L of each compound

in the la bor a t or y

f

o r tif ic a tion sa mple

.

5.4.5 Internal standard

solution —Prepare an internal standard

solution of Monuron and dichloroacetic acid at concentrations of 0.1 and 1.0 mg /mL

, respect i v el y , accordi n g t o t h e fol l o wi ng form ul a:



##    



ss t

ss 

## C V C V t (4)

w h ere V ss 

### = the aliquot v o lum e required,

in m i croliters;

C

t 

### = targ et concentration,

ty

pically 100 ng / μ L;

V

t 

### = v o lum e of targ et solution required, in m illiliters (100 m L for this solution);

and

C

ss 

### = the com pound standard
solution concentration, in

m illig ram / m illiliter (1,000 ng /μL for this solution). 

### 5.4.6 C alibration solutions —A

se t of qua ntita tive c a libr a tion solutions is

anal y z ed and a cal i b rat i on curve i s g e nerat e d at the beg i nning of analy s is to determine the

c onc e n tr a tions of qua lita tive l y ide n tif ie d compounds. To do this, prepare a series of working standard solutions, rang ing in concentration from 100 to 100,000 ng /L , from the stock solutions prepared in sections 5.4.1

and 5.4.2. At least five concentrations of calibration standards and a compound-free blank solution (sy s tem or instrument blank)

are anal y z ed. Each concent r at i on i s prepared as needed by addition of a specified volume

of the stock multicom ponent standards to produce standards with concentrations equivalent to 0.010, 0.050, 0.10, 0.20, 0.50,

and 1.00  g / L in wa te r
, a ssuming a n inje c tion

volume of 50  L and a 1.00-L water sample. The preparation of these standard solutions is

described in detail in the following sections.

5.4.6.1 W o rking standard solutions for calibration standard formulation . Mix 25 mL of surrog a te solution (5.4.3) with 25 mL of positive mix 1 and

neg a tive mix (5.4.1) in separate 50-mL

volumetric flasks. The concentration of this intermediate solution is 10,000 μg /L

. P r epare the wor k ing sta nda r d s f o r

positive mix 1 a nd

neg a tive mix by using the 10,000-μg /L

inte r m e d ia te solutions a nd the dilutions liste d in table 5(A). Prepare working standards for positive mix 2 using the 10,000-μg /L

inte r m e d ia te solution a nd the dilutions liste d in table 5(B )

.

AN AL Y T I C AL M E T H O D 1 7

### 5.4.6.2 Calibration standards.

Calibration standards are prepared j u st pri o r to instrumental analy s is. Measure 900 μL of

org a nic-free water (5.1.8) into the number of vials required for the desired number of calibration standards. Add 100 μL of a

worki n g st andard sol u t i on t o each vi al . Add 5 μL of qua ntita tion inte r n a l sta nda r d solution (5.4.5), cap, and mix . Note that for ease of sample concen tration determination,

t h e cal i b rat i on st andard concent r at i ons are

ex pressed by an equiva lent concentration in a 1,000-mL water sample (sample equivalence). The concentration of the

c a libr a tion sta nda r d s is calculated by using

the f o llowing f o r

m ula e
, in whic h the dilution of a 5,000-μg /L working standard to a 0.5-μg /L (sample equi valence) calibration

standard is listed:

(A) 100 μL of working standard (5,000 μg/L) is added to 900 μL of organic-free water:

5,000 μg /L x 100 μL x L/10 6 

### μL = 0.5 μg 0.5 μg /m L x 1,000 m L /L = 500 μg /L in v i al



### (B) On-colum n m a ss of standard m ade in (A), when using a 50-μL injection:

500 μg /L x 50 μL x L/10 6 

### μL = 0.025 μg on colum n 0.025 μg on colum n x 1,000 ng /μg = 25 ng on colum n



### (

C

) Conc e n tration of c a libration standard (sam ple equ i val e n ce):

25 ng x 1,000- μL v i al/50 μL inj ected x 1/1,000 m L = 0.5 ng /m L 0.5 ng /m L x 1,000 m L /L x 1 μg /1,000 ng = 0.5 μg /L (calibration standard' s concentration equiv a lence in a 1- L water sam p le)

T a b l e 5. Volum e dilutions f o r m e thod w o r k ing s t andar ds

[m L

, m illiliter; μg /L , m i cro g ram p e r liter; μL , m i cro liter]

Vo lu met r ic f l ask u sed ( m L ) Vo lu me o f 10,000 μg /L

st an d a rd u sed ( μ L ) Fina l c onc e n tr a t ion of

w o r k ing s t a nda r d (μg/L)

(A) W o rk in g s t an dards f o r pos itiv e m i x 1 an d n e g a tiv e m i x u s in g th e 10,000- μg /L s o lu tion

1 0 5

, 0 0 0 5

, 0 0 0

2 5 5

, 0 0 0 2

, 0 0 0

5 0 5

, 0 0 0 1

, 0 0 0

1 0 0 5

, 0 0 0 5 0 0

2 0 0 2

, 0 0 0 1 0 0

(B) W o rk in g s t an dard dilu tion s f o r pos itiv e m i x 2 u s in g th e 20,000- μg /L s o lu tion

1 0 5

, 0 0 0 1 0

, 0 0 0

1 0 2

, 5 0 0 5

, 0 0 0

2 5 2

, 5 0 0 2

, 0 0 0

1 0 0 2

, 5 0 0 5 0 0

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 18

### 5.4.6.3 Concentration of

calibration standards. W o rki n g st andard

concentrations and thei r sample equivalence

a r e liste d in ta ble 6.

T a b l e 6. W o r k ing s t andar d c onc entr a tions and equivalent s a m p le c onc entr a tions f o r this m e thod

[μg / L

, m i cro g ram p e r liter]

Wor k ing s t a nda r d

co n cen t r at io n (μg/L) E quiv a le nt s a m ple

co n cen t r at io n (μg/L)

1 0

, 0 0 0 1

. 0 0

5

, 0 0 0

. 5 0

2

, 0 0 0

. 2 0

1

, 0 0 0

. 1 0

5 0 0

. 0 5

1 0 0

. 0 1

5 0

. 0 0 5



### 5.4.7 T h i r d-part y check

solution —An independently verified or

" t hird-party " standard solution, containing the same or a subset of the compounds in the

calibration standard solutions dissolved in methanol, can be used to determine

accept a bl e perform ance of t h e i n st rum e nt
calibration. This solution should not contain the method internal standards or surrog a tes. I f available, obtain this solution from a vendor that has prepared a solution and has independently validated it by instrumental

anal y s i s . S t ore t h i s sol u t i on i n a freez er at

 15°C, being sure to use the solution prior to

the manufacturer’s ex piration date. Select a concentration near the midpoint of the method
calibration rang e (0.1 to 0.5  g / L ) . Use this

concentration to determine the volume of

solution r e quir e d to f o r tif y

a

1- L wa te r sa mple

to the chosen concentration. F o r ex ample, theconcentration of the components in thirdparty check solution used in this study was

17.5  g / L

. Add 10  L of the third-party

standard to 990  L of water in a 1.5-mL

am ber-g l a ss screw-cap au tosampler vial and 5

 L of the inte r n a l sta nda r d solution to produce a per-component solution concentration of 0.175 μg /L . Then seal the vial with a Teflon-lined septum cap, and add to the sequence of sa mple, calibration, and

qua lity

- c ontr o l sa mple s. The c onc e n tr a tion of the third-party standard solution should be

suf f i c i e n tly hig h so tha t the solve n t in the aliquot that is diluted will not affect chromatog r aphic separation.

5.4.8 I n strume nt quality

- c ontrol

standards —The two instr u me nt qua lity

- c ontr o l

standards that monitor i n st rum e nt perform ance over the course of analy s is are continuing

calibration verification standards (CCVs) and continuing calibration blanks (CCB s). The

CCVs a r e inte r s pe r s e d within a se t of sa mple s and are used to verify that the instrument has

sta y e d within a n a l y tic a l c a libr a tion ove r the course of analy s is. The CCB s are monitored to

de te r mine if sa mple or sta nda r d inje c tions

caused cross-contamination.

5.4.8.1 Continuing calibration verification ( CCV) standards . Prepare a 0.2-

μg /L midc a libr a tion- le ve l- c h e c k sa mple by adding an appropriate amount of the

calibration standard for the ioniz a tion mode to be analy z ed into an appropriate amount of

or g a nic

- f r e e wa te r in a n a u tosa mple r via l

. Add 5  L of the internal standard (5.4.5), and seal with a Teflon-lined septum cap. Concentrations other than 0.2 μg /L may be used for CCVs if desired, as long as the concentration is near the midpoint of the calibration rang e.

5.4.8.2 Continuing calibration blank ( CCB) standards . P l ace 1,000 μ L of

or g a nic

- f r e e wa te r in a n a u tosa mple r via l

.

NOT E : Do not add internal standard solution

to the CCB . Seal with a Teflon-lined septum

cap.

6. Saf e t y Precaut i ons

6.1 Use a well-vented fume hood for all steps involving org a nic solvents and acids.

AN AL Y T I C AL M E T H O D 1 9

### 6.2 W ear ey e protection and the appropriate ty pe of g l oves when using any

reag ent s

.

6.3 Ensure that the electrospray waste

ex haust tube and the vacuum pump ex haust tube of the mass spectrometer are vented out

of the ambient laborator y

atmosphere throug h

ve ntila tion duc ting e x pr e ssly spe c i f i e d f

o r

tha t

purpose.

7. Procedure

7.1 Sample filtration

This method is applicable only to filtered water samples. All samples should be

f ilte r e d in the f i e l d, pr e f e r a b ly a t the time of

collection. F iltration will reduce the likelihood of compound deg r adation by

rem ovi ng part i c ul at e-associ at ed bact eri a

. Re mova l of pa r tic ula t e s a l so will pr e v e n t clog g i ng of the retain ing f r it a nd sta tiona r y phase of the solid-phase e x tr a c tion c a r tr idg e
, thus improving operation and ex traction efficiency . Sandstrom (1995) describes a USGS-approved filtrati on method appropriate for samples analy z ed by this method. Occasionally , samples ar e not filtered on site or become cloudy (particulate formation caused by chemical reactions or nanobacterial

g r owth) dur ing tr a n sit to the la bor a t or y

. F ilte r these cloudy samples at the laboratory according to the procedure outlined by Sandstrom (1995) by using a 14.2-cm filter

holde r a nd positive pr e ssur e pump. Use a 0.7-μm pore siz e , 14.2-cm diameter, g l assf i be r f

ilte r
, a s he d a t 440 C for 2 hours. F l ush the filtration appara tus with 100 mL of

L i quinox solution (5.2.4), 100 mL of org a nicfree water (5.1.8), 50 mL of methanol (5.1.5), and ag ain with 100 mL of org a nic-free water.

R e peat t h i s cl eani n g procedure bet w een samples. Use a separate filter for each sample to prevent sample cr oss-contamination.

7.2 Solid-phase ex traction cartridg e cleaning and conditioning N O TE: The ex traction and elution procedure used in this method was desig n ed to perform equally well by manua l operation or by

a

u toma te d SPE wor k sta tions. The sa me cleaning and conditioning procedure is used

for both.

7.2.1 Prepare, as needed, the 80-

percent m e t h y l ene chl o ri de/ 20-percent methanol (v/v) and 10-g / L aqueous ascorbic acid solutions for conditioning the SPE cartridg e s (5.2.1.1 and 5.2.1.2). These SPE cartridg e conditioning solutions are prepared once a week because evaporat i on m i g ht al t e r the solvent composition. Store the ascorbic

a c i d solution in the r e f r i g e r a tor a t a ll time s to
prevent prem at ure deg r adat i on of t h e aci d.

7.2.2 The performance of Supelco Graphitiz ed carbon-based SPE (6-

mL ) c a r tr idg e s ma y va r y

f

r o m lot to lot. B e

sur e to use c a r tr idg e s f r o m a sing le lot f o r

a n y set of environmental and QC sa mple s. I n sta ll the g r aphitiz ed carbon-based SPE cartridg es on the vacuum ex traction manifold. The vacuum pump is used to pull the first two conditioning solutions throug h the cartridg e

. Do not ex ceed 20 m m Hg vacuum pressure,

or

the e x tr a c tion c h a m be r will implode

.

7.2.3 Cartridg es are conditioned by

se que ntia lly e l uting the c a r tr idg e with two

5-mL aliquots of 80-percent methy l ene chloride/20-percent me thanol (v/v) (5.2.1.1) with the vacuum pump to facilitate elution. This step is followed by elution with 5 mL of methanol (5.1.5) throug h each cartridg e using the vacuum pump. Eluting three 5-mL aliquots of the ascorbic acid solution (5.2.1.2) under

g r avity flow completes conditioning . The ascorbic acid conditioning step should take pl ace sl owl y t o ensure act i v at i on of bi ndi ng site s in the c a r tr idg e be d. Keep the flow rate of

ascorbic acid solution at no more than 3

mL /min. Cove r c onditione d c a r tr idg e s with f o il

a nd se t a s ide until r e a d y f

o r

use

. Ca r t r i dg e s c a n be used up to 8 hours after conditioning

. Cartridg es that have not been used within 8

hours need to be reconditioned. Collect the

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 20

### conditioning solvents in the vacuum manifold; pl ace t h ese sol v ent s i n a chl o ri nat e d wast e container for proper disposal.

N O TE: To avoid deactivation of the SPE sorbent surface, cartridg e s should never be allowed to dry after conditioning

.

7.3 Solid- pha se e x tr a c tion

N O TE: The following description is for the

automated SPE workstation method. This method can be carried out manually throug h the elution step by using the same conditions

outline d in the f o llowing pr oc e dur e

.

7.3.1 Prior to ex traction, the

a

ppr ox ima te pH of the sa mple is de te r mine d by removing a small (0.05 mL ) aliquot with a disposable Pasteur pipe t (4.7.5) and apply i ng the volume to pH paper with a rang e of 0 to 14, and recording the pH. Do not adjust the

sa mple pH. Re c o r d the c o mbine d sa mple a nd bottle weig ht. Note any unusual appearance of the sample and record it. Add 100 μL of

surrog a te solution (5.4.3) and 1 g of sodium

chl o ri de (NaC l ) t o each sam p l e . S h ake

sa mple s we ll to dissolve the Na Cl a nd uniformly disperse and mix the surrog a te.

7.3.2 Prepare laboratory reag ent blank (L RB ) and laboratory reag ent spike ( L RS) sa mple s. Obta in two c l e a n e d a nd

bur ne d 1- L a m be r bottle s. F ill the m with 1,000 mL org a nic-free water and add 1 g of

NaCl to each bottle. Shake well to dissolve

the Na Cl. I n pr e p a r ing the f o r tif ic a tion sample, add 100 μ L each of the three multicomponent matrix fo rtification solutions to one bottle containing 1,000 mL of reag ent

wa te r

. Re c o r d the solution c ode a nd bottle preparation date of the f o r tif ic a tion solutions (section 5.4.4). Add 100 μL of surrog a te solution to each bottle (5.4.3). This step will

r e sult in a f

i na l c onc e n tr a tion in the se t

fortification of 0.25  g / L

. S h ake t h e fortification and blank vig o rously to mix the

surrog a te and NaCl in the water. L a boratory

reag ent bl ank and reag ent spi k e sam p l e s m u st be prepared wi t h each set of envi ronm ent a l

sa mple s. A se t of sa mple s in this pr oc e dur e consi s t s of t h e reag ent spi k e and reag ent blank samples and up to 10 environmental

sa mple s. The e nvir onme n ta l sa mple tota l

may include duplicate fi eld samples or field

sa mple s tha t a r e to be f o r tif ie d in the

la

bor a t or y

( l a bor a t or y

ma tr ix spike sa mple s)

. Most analy t es are st able under refrig e ration for up to 4 day s prior to ex traction on the

ba sis of r e sults f r o m on- g o ing holding

- time

studies.

7.3.3 Clean the AutoTrace pumps and tubing prior to use by flushing each AutoTrace position with sequential aliquots of 50 mL of L i quinox deterg ent solution (5.2.4), 50 mL of water (5.1.8), and

50 mL of methanol ( 5.1.5). Pass nitrog en throug h the lines at about 103.4 kPa (15 pounds per square inch) for about 5 minutes

t o ensure t h at al l t r aces of m e t h anol are removed.

7.3.4 I n stall six conditioned, 6-

mL g r aphitiz ed carbon- based SPE cartridg e s (4.7.2) on the AutoTrace S P E workstation.

Attach one SPE cartrid g e connector and one

of the 6-mL poly p ropy lene sy ring e barrel adapt e rs t o each cart r i d g e . L o wer t h e pl ung er/ cart r i d g e cl am p i n t o t h e adapt e r, t hus

e n sur i ng tha t the e n tir e a sse mbly f

its snug ly in the apparatus. I t is critical that the plung er is lowe r e d f u lly a nd snug ly into the a d a p te r because t h i s snug fi t

, and t h e pl ung er O-ri ng
, are t h e pri m a ry m eans for seal i n g t h e S P E

c a r tr idg e into the f l ow str e a m f o r

SPE loa d ing

and elution. L e aks caused by poor sealing will adversely and i rreproducibly affect method performance.

7.3.5 Pump water samples throug h the conditioned cartridg e s by using a flow rate of 20 mL /min. Approx imate

e x tr a c tion time f o r

1 L of sa mple is 50

minutes. The AutoTrace workstation will emit an audible sig n al and suspend operation when

e x tr a c tion is c o mple te

.

AN AL Y T I C AL M E T H O D 2 1

### 7.3.6 Upon completion of

ex traction, the SPE cartridg e s require dry i ng

. Two methods have been used with equal success. The first is to pass nitrog en g a s thr oug h the c a r tr idg e , f o llowe d by c h e mic a l dry i ng of the cartridg e with me tha nol. Af te r

some ex perimentation, it was found that the

nitr og e n g a s ste p c ould be omitte d. This optional nitrog en g a s-dry i ng step is described in the following section. The methanol dry i ng procedure is ex plained in section 7.3.8.

7.3.6.1 Optional nitrogen gas drying. P l ace em pt y pl ast i c t e st t ubes i n t h e Aut o Trace el uent col l ect i on rack. C ont i nue AutoTrace operation, and the prog rammed

ste p f o r

nitr og e n f l ow will be g i n. Nitr og e n will flow at a pressure of 103 kPa for 1 minute. Remove the empty poly e thy l ene test tubes and dispose of the r e sidua l wa te r

. R e m ove cart r i d g e s from t h e Aut o Trace and attach to nitrog en manifold. Dry for at least

15 minutes at 550 to 620 kPa. Return to appropri a t e posi t i ons on t h e Aut o Trace.

7.3.7 W e ig h the empty sample

bottle a nd r e c o r d the we ig ht. The dif f e r e nc e be twe e n this we ig ht a nd the initia l bottle weig ht (7.3.1) provides the sample mass in

g r a m s, whic h is a ssume d to be equal to the

sa mple volume in millilite r s . Note tha t this procedure assumes that the volumetric density

of

a

ty pic a l f r e shwa te r sa mple is 1 g /mL . F o r

sam p l e s col l ect ed from sal i n e envi ronm ent s , a salinity or density de termination should be made and a volume correction applied.

Occasionally a cartridg e will clog

,

e v e n if a

sa mple ha s be e n f ilte r e d. This is

l i k el y t h e resul t of adsorpt i on of coex t r act ed

na tur a l or g a nic ma tte r ont o the cartridg e bed.

I n this e v e n t, the e n tir e sa mple ma ss ma y not
ha ve be e n e x tr a c t e d. We ig h the bottle a nd

r e ma ining sa mple , disc a r d the r e ma ining

sa mple a nd r e

- w e i g h the e m pty bottle

. Record these results and this condition. This

i n form at i on i s requi red t o accurat e l y determine sample concentration. 7.3.8 SPE c a r tr idg e e l ution

7.3.8.1 After sample loading and the optional nitrog en g a s dry i ng step, cartridg e s retain a small amount (  0.1 mL ) of

r e sidua l wa te r

. Che mic a lly dr y

the c a r tr idg e by eluting the analy t es with 1.5 mL of methanol. Some compounds are eluted in this

fraction. This 1.5-mL fraction is collected separately in unused pol y p ropy lene test tubes by placing six tubes positioned in the

Aut o Trace rack and l a bel e d wi t h t h e

a

ppr opr ia te sa mple ide n tif ic a tions. I n addition, this label should also include the

le tte r “ M ” to indic a t e tha t this is the me tha nol fraction. Start the first step of the AutoTrace elution prog ram to beg i n collection of the

“M” fract i on for al l si x t ubes. W h en t h e Aut o Trace has com p l e t e d t h i s fi rst part of t h e elution, it will emit an audible sig n al. The last drops of methanol in the cartridg e bed are removed by passing nitrog en g a s throug h the cartridg e at 103 kPa for 30 seconds. W h en

t h e Aut o Trace has com p l e t e d t h i s m e t h anol

dr

y i ng ste p, it will e mit a n a udible sig n a l

. R e m ove t h e “M” fract i ons from t h e Aut o Trace rack and bri n g t h e fract i on t o a volume of 1 mL with org a nic-free water.

Re f r i g e r a te the e x tr a c t until c o mple tion of

elution.

7.3.8.2 Most of the analy t es are collected in the second elution fraction of the

S P E cartridg e . P l ace unused poly p ropy lene

test tubes in the elution rack of the AutoTrace

workstation to collect the second elution

fraction. L a bel these tubes with the

a

ppr opr ia te sa mple ide n tifications. I ndicate

that these tubes hold the second elution

fract i on by l a bel i n g each t ube wi t h an “E”. Make sure the tubes are arrang ed in the correct order so that they will receive the eluent from appropriate S P E cart r i d g e s. El ut e each S P E cartridg e with three aliquots of 80-

percent m e t h y l ene chl o ri de/ 20-percent methanol (v/v) with 0.2 percent trifluoroacetic acid anhy dride (TF A ) solution (5.2.2).

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 22

### The three aliquot volumes are, in sequence, 5, 5, and 3 mL . This elution sequence is prog rammed for automated operation by the AutoTrace workstation. Eluting with three aliquots improves analy t e recoveries compared to continuous elution with a sing le 13-mL aliquot. Start the “E”

el ut i on port i on of t h e Aut o Trace sequence.

Note: I f performing this method manually , do not let the cartridg e beds dry

. W h en the elutions of the three aliquots for each sample are completed, the AutoTrace will emit an

audi bl e si g n al . R e m ove t h e “E” ex t r act t ubes

from t h e Aut o Trace rack, cover wi t h foi l

, and

se t a s ide in a r e f r i g e r a tor until it is time f o r the concentration step.

7.3.8.3 The fluid-flow paths of the

Aut o Trace workst at i on consi s t of poly t etrafluoroethy l ene tubing , which may adsorb nonpolar analy t es. A postex t raction

cl eani n g of t h e Aut o Trace workst at i on (or

ma nua l SPE e x tr a c tion a ppa r a tus) is the r e f or e required and should be performed immediately after elution. Discard the SPE

sam p l e cart r i d g e s, and seal t h e em pt y adapt e r

c a r tr idg e s into the e l ution sta tions. Wa sh

each of t h e si x Aut o Trace concent r at i on and

elution stations with 50 mL of L i quinox deterg ent solution, 50 mL of water, and 50

mL of methanol, at a flow rate of 20 mL /min.

7.3.9 Concentration

7.3.9.1 B e fore concentration, add

10  L of a 10-percent w/v sodium hy drox ide solution (5.2.3) to the “E” fractions of the

sa mple s. This is a dde d to ne utr a lize the TF A

i n t h e el uent and reduce pot ent i a l anal y t e deg r adation during volume reduction.

7.3.9.2 The two fractions are reduced in volume under a nitrog en g a s

vort e x st ream . To reduce vol um e, pl ace t h e “M” and “E” fract i on t ubes i n t o t h e TurboVap

sa mple c onc e n tr a tion a ppa r a tus. Sa mple s a r e concentrated under a nitrog en g a s stream of
69 kPa (10 lb/in 2 

### ) while kept at 34 C in a water bath. The volume of the “E” fraction is

about 13 mL , which nearly fills the 15-mL volume of the test tube. The nitrog en g a s pressure i s t h erefore i n creased sl owl y from 0 to 69 kPa, while monitoring the behavior of the fractions in the TurboVap. This prevents ej ect i n g a port i on of t h e “E” ex t r act from t h e tube into the TurboVap water bath or into other samples, which mig ht cause crosscontamination. W h en tubes are initially pl aced i n t h e TurboVap, t h ey are spaced apart

a s muc h a s possible to minimize pote n tia l cross-contamination. TurboVap noz z l es should be cleaned between samples. Note

tha t the se tting s f o r

ba th te mpe r a t ur e a nd

nitr og e n pr e ssur e a r e optimize d f

o r

a n a l y t e

r e c ove r y

within a r e a s ona ble tota l time f o r

ex tract volume reduction. Ex ceeding the

spe c i f i e d te mpe r a t ur e or pr e ssur e se tting s will adversely affect compound recoveries.

7.3.9.3 The “M” fraction will take

30 minutes to concentrate to about

400 μ L because of t h e vol um e of wat e r i n t h e fraction. Carefully monitor the fraction

reduction and do not allow the ex tracts to dry

,

or

a n a l y t e r e c ove r i e s will be a dve r s e l y affected. Take the “M” fraction out of the TurboVap after 30 minut es of concentration

time a nd c ove r with f o il. Se t the “ M ” f r a c tion

a s ide in the r e f r i g e r a tor until the via ling process is to beg i n.

7.3.9.4 The “E” fraction will normally take 45 to 60 minutes to

concent r at e. Al l o w t h e “E” fract i on t o concentrate for 30 minutes along with the

“M” ex t r act . Aft e r t h e “M” ex t r act has been

concentrated and removed from the TurboVap, continue to concentrate the “E”

fraction for an additional 15 minutes. Concentrate the sample to about 400 μ L.

Ca r e f u lly monitor the fraction reduction and

do not allow ex tract volume to decrease to

less than 400 μ L

, or a n a l y t e r e c ove r i e s will be

adversel y affect ed. I f t h e ex t r act has been

concent r at ed for 60 m i nut es and t h e ex t r act s

AN AL Y T I C AL M E T H O D 2 3

### are g r eater than 400 μ L

, however, t h ere m a y be r e sidua l me thy l e n e c h lor i de in the “ E ”

ex tract. I f this occurs, g o to step 7.3.9.5. I f

the r e is no r e sidua l me thy l e n e c h lor i de in the

“E” ex t r act , t h en t h e concent r at ed sam p l e i s ready t o be com b i n ed wi t h t h e “M” ex t r act
and t o be pl aced i n a sam p l e vi al for

i n st rum e nt al anal y s i s

.

7.3.9.5 I f the “E” fraction contains methy l ene chloride, it must be removed to avoid altering the chromatog r aphi c separat i on of anal y t es and decreased

anal y t e recoveri es. Ty pi cal l y , m e t h y l ene

c h lor i de is pr e s e n t a s a n immisc i ble la y e r underneath the aqueous phase or as small bubbles at the bottom of the test tube, or as a cloudy or “milky ” appearance. As this description indicates , t h e presence of

me thy l e n e c h lor i de in a sa mple ma y be ba r e ly

percept i b l e , so each sam p l e m u st be careful l y

ex am i n ed for t h e presence of m e t h y l ene chloride. I f a test tube is determined to

cont ai n m e t h y l ene chl o ri de, evaporat e t h e volume in the test tube to about 400 μ L

. Then

add about 200 to 300 μ L of org a nic-free water

and mix with a vortex i ng mix er. Evaporate the liquid in the test tube down to 400 μ L

a g a i n. Re pe a t this pr oc e ss until the r e is no

mor e me thy l e n e c h lor i de in the te st tube

. Not e for each sam p l e where t r eat m e nt t o

r e move r e sidua l me thy l e n e c h lor i de is required.

7.3.10 Sa mple tr a n sf e r

into via l s and preparation prior to analy s is

7.3.10.1 Use clean and preashed 1.5-mL amber sc rew-top autosampler

vials.

7.3.10.2 L a bel each vial with

a

ppr opr ia te la b ide n tif i cation and set number.

This inf o r

m a tion is impor ta nt f o r

e v a l ua ting

individua l sa mple r e sults by c o mpa r ison to se t quality -control sample s (duplicates, set blanks, set reag ent fortifications). 7.3.10.3 Pair the “M” and “E”

ex t r act s for each sam p l e . Bri e fl y swi r l t h e “M” fractions with a vortex i ng mix er to wash

the te st tube wa lls. Tr ansfer the contents of

t h e “M” ex t r act t ube i n t o t h e “E” ex t r act t ube by using a silicone-rubbe r bulb and a separate cleaned and burned disposable Pasteur pipet (4.7.5) for each sample. I f the sample appears “cloudy ,” methy l ene chloride may be present

a nd the sa mple will ne e d f

u r t he r concentration to rem ove it (section 7.3.9.5).

Mi x t h e com b i n ed “M” and “E” fract i ons wi t h

a vort e x i ng m i x er and t r ansfer t h e ex t r act i n t o the a ppr opr ia te sa mple vi al by using the same pipe t tha t wa s use d f

o r

c o mbining the two fractions. Repeat this procedure for the entire

sa mple se t.

7.3.10.4 Ensure that the final

combined ex tract volume is about 1,000 μ L by comparison to a vial with a known volume of liquid. An ex act volume is not required because quantitation is by internal standard.

I f

the final sample volume is less than 900 μ L,

di l u t e t o vol um e wi t h org a ni c-free wat e r. S eal vials with screw cap by ensuring a tig ht seal but not so tig ht that the Teflon-lined septum is puckered or wrinkled, whic h c a n r e sult in

evaporat i on of t h e sam p l e . P l ace t h e vi al s i n a vial tray , org a niz e d by set. Store sample

ex tracts in a freez er at –14oC until analy z ed.

7.3.10.5 J u st prior to analy s is, inject 5 μL of the internal standard solution (5.4.5) into each vial throug h the septa, using a dedicated 10-μL sy ring e (4.6.1). The

inte r n a l sta nda r d is a dde d to a ll sa mple s, including the L R S and the L R B

. The internal

standard solution contains the internal

sta nda r d s f o r

both positive a nd ne g a tive analy s is, and is only added once. The same

volume of internal standard is added to the

instr u me nt c a libr a tion solutions a nd continuing calibration verification solutions

a n a l y z e d with the e nvir onme n ta l sa mple s. These sam p l e s and t h e sequence t h ey are analy z ed in are discussed in section 7.4.2.5.2.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 24

### 7.4 I n strumental analy s is

7.4.1 I n st rum e nt al anal y s i s overview—The analy t es contained in sample

ex t r act s are separat e d by HP L C wi t h a reverse-phase octadecy lsila ne c o lumn a nd water:acetonitrile g r adient elution. The separated components ar e transported in a

fl owi n g st ream t o t h e el ect rospray i oni z a t i on interface. I n the interface, compounds, solvent, and any coeluting components of the

sa mple ma tr ix a r e ne bulize d into sma ll droplets and desolvated. During desolvation, compounds are ioniz e d by charg e adduction, ion evaporation, or a combination of protonating processes (Kebarle and Ho, 1997). The ioniz e d compounds are separated from the neutral compounds by means of a  3 kV potential difference between the

nebul i z i n g el ect rospray needl e and t h e apert u re l eadi n g t o t h e m a ss anal y z er. The

nebuliz ed neutral compounds do not enter the mass spectrometer, but rather they condense

with the solve n t a nd dr a i n to a wa ste
reservoir.

The ions tr a n sit thr oug h the capillary aperture, and, as they ex it the capillary to a redu ced (1 to 2 millitorr)

pressure reg i on, are subject to an accelerating

volta g e ( c a lle d a f

r a g m e n tor volta g e or

c a p illa r y

e x it volta g e by some ma nuf a c

t u rers). Thi s accel erat i n g vol t a g e provi des

the ions with suf f i c i e n t mome ntum to induc e f r a g m e n ta tion by c o llision with ne utr a l nitrog en g a s molecules. The ioniz e d

f r a g m e n ts a r e swe p t f r o m this low- pr e ssur e

r e g i on to the ma ss spe c t r o me te r by momentum from a pressure difference between the low-pressure reg i on and the analy z er reg i on. Electrostatic lenses collimate the ions, and a quadrupole mass

anal y z er i s used sel ect i v el y t o t r ansport i ons of a speci fi c m a ss-t o -charg e rat i o t o a continuous electron multiplier. The current induced by the impact of the ion on the multiplie r sur f a c e is a m plif ie d a nd tr a n smitte d as a voltag e sig n al, with the number of ions proportional to the total voltag e of the sig n al.

Time

- p r o g r a mme d, se le c t e d

- i on monitor i ng is

use d to ma x imize de te c t a b ility of spe c i f i c ions and reduce chemical noise from

c o e l uting inte r f e r e nc e s

.

Coordinated, automated

c o mpute r ize d pr og r a mming is use d to c ontr o l most aspects of chromatog r aphic separation,

ioniz a tion, frag m entation, ion focusing , mass analy s is, detection, and data handling

. A

ty

pical separation of a st andard mix ture of the compounds determined under positive

ioniz a tion conditions is shown in fig u re 1.

Not e t h at coel ut i n g peaks are not

di st i n g u i s hed because t h i s i s a reconst r uct e d ion chromatog r am of selected-ion monitoring results. These coeluting peaks would be

se pa r a te d a nd ide n tif ie d by using Targ et Software or equivale nt automated g r aphic

da ta

- h a ndling sof t wa r e . A simila r chromatog r am can be produced for compounds eluting under neg a tive ioniz a tion

conditions.

7.4.2 Hig h -performance liquid chromatog r aphic separation

7.4.2.1 S a mple vials are placed in

t h e aut o sam p l e r of ei t h er a Hewl et t

- P ackard

1090 Series I I HPL C or a HewlettPackard/Ag ilent Technolog ies Series 1100

HPL C . The a u tosa mple r te mpe r a t ur e is ke pt

a t 4oC e ithe r by r e c i r c ula ting f l uid c h ille r ( f o r the HP 1090 Series I I HPL C ; Neslab

Coolflow CF T-33 or equivalent) or by a Pe ltie r c ooling unit ( H e w le tt- Pa c k a r d/Ag ile nt Technolog ies 1100 Series HPL C autosampler). A 50-μL aliquot of the sample

e x tr a c t is inje c t e d into the HPL C e l ue nt stream to start separation.

AN AL Y T I C AL M E T H O D 2 526 Pest i c i d es i n Wat e r by Gra phi ti z e d C a rbonB ased SPE and H P LC / M SFigure1.Chromatogramofa positive ion standard used in thismethod.

### 7.4.2.2 The analy tical separation for the method is carried out by using a reverse-phase octad e c y lsila ne c o lumn (MetaChem Technolog ies I n ertsil ODS-3, particle siz e of 5 μm, column dimensions of 2 mm inside diameter by 150 mm long or equivalent). An integ r al g u ard column (MetaChem Technolog ies Metag u ard

I n e r tsil ODS- 3, pa r tic le siz e of 5 μm, 2 mm inside diameter or equiva lent) also is used.

7.4.2.3 The separation is carried out using a binary eluent sy stem of (1)

org a nic-free water modified with ammonium acetate and formic acid (3.6 millimolar ammonium acetate; 5.22

millimola r f

o r

mic a c i d; Mobile Pha s e A; se e section 5.3.2 for preparation), and (2)

acet oni t r i l e m odi fi ed wi t h am m oni um acetate (3.6 millimolar; Mobile Phase B ; see section 5.3.1 for preparation). I n itial HPL C conditions follow: Autosampler, 4°C; column oven, 40°C; binary mobile phases (Mobile Phases A and B ; sections 5.3.1 and 5.3.2). The combined mobile-phase flow

rate is constant at 0.20 mL /min. The

mobile

- pha se g r a d ie nt use d f

o r

both positive and neg a tive ioniz a tion analy s es is listed in

table 7. Each HPL C analy s is requires 85 minutes to complete, including a posta n a l y s is c o lumn r e

- e quilibr a tion pe r i od of

11 minutes. HPL C separation and mass

spect rom e t r i c (MS ) anal y s i s are synchroniz e d by computer control at the start of

each anal y s i s . For each HP L C / M S sy st em
, spe c i f i c e l ution c o mpositions a nd time s a r e te ste d ite r a tive l y to a c h ie ve optima lseparation, so the specific times and mobilephase compositions listed in table 7 should be used as a starting poi nt for developing an acceptable separation.

T a b l e 7. High- per f o r m anc e liquid c h r o m a togr aph

m obile- phas e gr adient f o r this m e thod

T i me, in

minute s Percen t a g e of mobile

p h ase A Percen t a g e of mobile

p h ase B

0

. 0 0 9 6

. 0 4

. 0

0

. 5 0 9 6

. 0 4

. 0

2 0

. 5 0 7 9

. 0 2 1

. 0

6 3

. 5 0 3 2

. 4 6 7

. 6

6 8

. 0 0 0

. 0 1 0 0

. 0

7 2

. 0 0 0

. 0 1 0 0

. 0

7 4

. 0 0 9 6

. 0 4

. 0



### 7.4.2.4 Mass spectral analy s is

pa r a me te r s

7.4.2.4.1 Ionization source operating conditions —The mass spectrometer ioniz a tion source conditions

f o r

both positive a nd ne g a tive ioniza tion

anal y s es are l i s t e d i n t a bl e 8. These conditions are held constant during the

anal y s i s

.

7.4.2.4.2 Programmable conditions during positive ion analysis— The com put ercontrolled aspects of mass spectrometer

ope r a tion dur ing positive ion a n a l y s is a r e liste d in table 9a. These time-prog r amming conditions

a r e sy nc hr onize d with the HPL C pr og r a mming

at t h e st art of each anal y s i s

.

T a b l e 8. Mas s s pec tr om eter oper ating c onditions dur ing pos itive and negative i oniz a tion analy s es us ed

in this m e thod

N i t r og en dry g a s t e m p erat u r e 350 deg r ees C e l s i u s Dry i n g g a s f l o w rate 1 0

. 0 liters p e r m i n u t e N e bu l i zer g a s pres s u r e 212 t o 414 k i l opas cal s [30 t o 60 pou n d s per s q u a re in ch (g as ); optim ized f o r each in s t ru m e n t ]

P o ten tial dif f e ren ce betw een n e bu lizer an d capillary

- 3 ,500 v o lts (polarity of v o ltag e rev e rs es f o r n e g a tiv e ion s )

AN AL Y T I C AL M E T H O D 2 7T a b l e 9a. Mas s s pec tr om eter tim e

- p r ogr am m ed oper ating c onditions f o r individual c o m pounds

deter m i ned under pos itive ioniz a tion c onditions

[m /z, m a s s

- to- c h a rg e ratio]

Ti m e ,

in

minute s Select ed

- i o n

gr oup 1 Select ed

- i o n monitor i ng ion

mass, in m/z T y p i cal

elect ro met e r

ga in Fr a g me ntor

v o lt ag e, in v o lts Indiv i dua l

ion dw e ll time, in

milliseconds

1

. 0 0 1 1 4 2 2 7 0 4 0 0

7.00 2 106, 108, 132, 133 163, 164, 185,207 2 5 0 4 8

16.11 3 106, 163, 174, 175 176, 195, 196, 198 199, 220, 223, 237 238, 240 2 4 0 2 7

22.70 4 146, 160, 161, 163 165, 166, 175, 181 188, 190, 192, 198 199, 209, 220, 256 312, 313, 326, 348 2 8 0 1 8

33.71 5 100, 116, 128, 151 167, 168, 172, 179 185, 187, 205, 213 229, 230, 236, 290 291, 312, 313, 411 412, 413 2 7 0 1 6

38.80 6 144, 161, 163, 199 201, 205, 207, 290 291, 312 2 9 0 4 3

41.92 7 111, 145, 146, 153 165, 167, 168, 202 216, 217, 218, 220 222, 223, 224, 233 234, 248, 280, 290 291, 365, 366 2 6 0 1 5

49.79 8 120, 134, 138, 149 155, 182, 220, 222 240, 241, 290, 291 304, 305, 306, 396

411 2 8 0 2 2

53.63 9 121, 122, 137, 160 169, 186, 213, 233 234, 249, 251, 415 2 7 5 3 1

57.79 10 160, 249, 251, 252 253, 254 2 3 5 6 5

60.56 11 114, 143, 160, 178, 249, 251, 275 277, 305, 342, 343 344, 347 2 8 5 2 9

67.03 12 134, 154, 216 2 80 132

1 Selected- i on g r ou p n u m ber ref e rs to s p ecif i c- m a s s ch arg e ratios m o n itored in a tim e in terv al.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 28

### 7.4.2.4.3 Programmable conditions during negative ion analysis

— The computer-controlled aspects of mass spectrometer operation during neg a tive ion analy s is are listed in table 9b. These timeprog ramming conditions are sy nchroniz e d

with the HPL C pr og r a mming a t the sta r t of

each anal y s i s

.

7.4.2.5 Mass spectrometer tuning and calibration

7.4.2.5.1 Mass spectrometer autotuning —Prior to any analy s is, the mass spectrometer is broug ht to temperature and

g a s pr e ssur e e quilibr i um, the n tune d to

ensure accurat e m a ss assi g n m e nt and a minimum detector response. An automated tuning (autotuning ) procedure is used, with proprietary tuning solutions (provided by the

instr u me nt ma nuf a c t ur e r ) f o r

positive a nd

neg a tive ion analy s is. The autotune procedure uses a proprietary alg o rithm that

c o mbine s the g a in a nd volta g e a pplie d to the instrument electron multiplier to produce the

m i n i m a l accept a bl e i on current across t h e

ma ss r a ng e of the ma ss spe c t r o me te r

.

The ions that must be present are listed in table 10, and the targ et peak width for acceptable tuning in positive and

neg a tive ion modes is listed in table 11.

Note tha t f o r

both positive a nd ne g a tive ion

mode s, the a u totune ma ss a x is c a libr a tion

must be within 0.13 atomic mass units (amu). I n addition, note that althoug h a

ty

pic a l e l e c t r o me te r g a in is liste d in ta ble s 9a and 9b, the appropria te electrometer g a in varies with the condition and ag e of the

e l e c t r on multiplie r in the ma ss spe c t r o me te r
, and the electrometer g a in listed should be used as a starting point.

T a b l e 9b

. Mas s s pec tr om eter tim e

- p r ogr am m ed oper ating c onditions f o r individual c o m pounds

deter m i ned under negative ioniz a tion c onditions

[m /z, m a s s

- to- c h a rg e ratio]

Ti m e ,

in

minute s Select ed

ion

gr oup 1 Select ed

- i o n monitor i ng ion

mass, in m/z T y p i cal

elect ro met e r

ga in Fr a g me ntor

v o lt ag e, in v o lts Indiv i dua l ion

dw ell time, in

milliseconds

7.00 1 146, 190, 192 2 45 192

13.00 2 195, 239, 241 2 45 192

1 8

. 0 0 3 1 7 5

, 1 7 7 2 4 5 2 8 9

30.00 4 239, 240, 241 2 45 192

37.00 5 141, 161, 195, 196 198, 199, 201, 203 218, 219, 221, 233 235, 253, 255, 271 273, 274, 275, 276

278 2 4 5 2 6

49.00 6 141, 143, 161, 163 217, 219, 227, 239

240 245, 247, 316, 318

360 2 4 5 4 3

1 Selected- i on g r ou p n u m ber ref e rs to s p ecif i c- m a s s ch arg e ratios m o n itored in a tim e in terv al.

AN AL Y T I C AL M E T H O D 2 9T a b l e 10. Q uantitation and c onf ir m a tion ions us ed f o r the c o m pounds deter m i ned

in this m e thod

[No t e th at th e ab sen ce o f an io n in d i cates th at f e w e r th an th ree io n s are u s ed f o r q u an titatio n an d

co n f irm a tio n

. ]

Compound Re te ntion time, in

minute s Qua n tita tion

ion Prim ary

c onfir ma tion

ion S e c onda r y

c onfir ma tion

ion

Co m p o unds a n a l y zed under po sit i v e io n co ndit i o n s 2,4- D m e t h y l es t e r 57.47 252 254

2- H y drox y a t r azi n e 2 0

. 8 9 1 9 8 1 9 9 3(4- ch l o roph en y l )- 1- m e t h y l u r e a 3 5

. 8 5 1 8 5 1 2 8 1 8 7

3- H y drox y carbof u r an 2 7

. 8 8 1 6 3 1 8 1 2 2 0

3- K e t o carbof u r an 3 6

. 6 6 1 7 9 2 3 6 1 5 1

A l di c a r b 3 5

. 5 1 1 1 6 2 1 3

A l di carb s u l f on e 17.35 240 223

A l di carb s u l f ox i d e 13.71 132 207

A t razi n e 4 5

. 6 7 2 1 6 2 1 8 2 1 7

Barban (In t e rn al S t d) 60.09 178 143

Ben d i o c a r b 4 2

. 8 2 1 6 7 2 2 4

Ben o m y l 2 4

. 5 7 1 9 2 1 6 0 1 6 1

Ben s u l f u ron

- m e t h l y 5 0

. 7 5 4 1 1 1 4 9 1 8 2

Brom aci l 3 7

. 9 2 2 0 5 2 0 7

C a f f e i n e 1 8

. 6 7 1 9 5 1 9 6

C a f f e i n e C 13 (i n t ern a l s t an dard) 18.66 198

C a rbary l 4 5

. 1 4 1 4 5 2 0 2 1 4 6

C a rbof u r an 4 2

. 8 0 2 2 2 1 6 5 2 2 3

C h l o ram b en m e t h y l es t e r 50.19 220 222

C h l o ri m u ron

- et h y l 5 5

. 0 5 4 1 5 1 8 6

C y cl oat e 6 7

. 9 4 2 1 6 1 3 4 1 5 4

D eet h y l a t r azi n e 2 8

. 4 3 1 8 8 1 9 0 1 4 6

D eet h y l d ei s opropy l a t r azi n e 5

. 1 1 1 4 2

D e i s opropy l a t r azi n e 2 0

. 7 9 1 7 4 1 7 6 1 7 5

D i ph en am i d 5 0

. 9 4 2 4 0 2 4 1 1 3 4

D i u r on 4 7

. 3 5 2 3 3 2 3 4

F e n u r on 2 6

. 5 9 1 6 5 1 6 6

F l u m et s u l a m 3 2

. 6 7 3 2 6 3 4 8

F l u o m e t u ron 4 5

. 5 6 2 3 3 2 3 4

Im azaqu i n 3 5

. 0 2 3 1 2 3 1 3

Im azeth a py r 3 1

. 9 6 2 9 0 2 9 1

Im i d i c l opri d 2 8

. 6 5 2 5 6 1 7 5 2 0 9

L i n u r on 5 4

. 5 9 2 4 9 2 5 1 1 6 0

Met a l a x y l 4 6

. 6 2 2 8 0 2 4 8 2 2 0

Met h i o c a r b 5 3

. 5 4 1 6 9 1 2 1 1 2 2

Met h om y l 1 8

. 9 4 1 6 3 1 0 6

Met h om y l ox i m e 10.51 106 108

Met s u l f u ron

- m e t h y l 3 8

. 8 3 1 6 7 1 6 8

Mon u r on (s u rrog a t e ) 38.68 199 201

N e bu ron 6 2

. 4 7 2 7 5 2 7 7 1 1 4

N i cos u l f u r on 3 6

. 6 1 4 1 1 2 1 3

N o rf l u razon 4 8

. 9 8 3 0 4 3 0 6 3 0 5

O r y zal i n 6 0

. 8 3 3 4 7 3 0 5

O x am y l 1 7

. 9 7 2 3 7 2 2 0 2 3 8

O x am y l ox i m e 1 2

. 0 6 1 6 3 1 8 5 1 6 4

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 30T a b l e 10. Q uantitation and c onf ir m a tion ions us ed f o r the c o m pounds deter m i ned

in this m e thod—Continued

Compound Re te ntion time, in

minute s Qua n tita tion

ion Prim ary

c onfir ma tion

ion S e c onda r y

c onfir ma tion

ion

Co m p o unds a n a l y zed under po sit i v e io n co ndit i o n s—Co nt inued
Proph am 4 9

. 8 8 1 3 8 1 2 0 Propi con azol e 6 1

. 3 3 3 4 2 3 4 4 3 4 3
Propox u r 4 2

. 1 0 1 6 8 1 1 1 1 5 3

S i du ron 5 3

. 0 6 2 3 3 2 3 4 1 3 7

S u l f om et u r on

- m et h y l 4 3

. 4 5 3 6 5 3 6 6

T e bu t h i u ron 3 6

. 4 7 2 2 9 1 7 2 2 3 0

T e rbaci l 3 8

. 9 1 1 6 1 1 6 3 1 4 4

T r i b en u r on

- m et h y l 5 0

. 5 3 1 5 5 3 9 6

Co m p o unds a n a l y zed under neg a t iv e io n co ndit i o n s 2,4,5- T 4 7

. 3 8 2 5 3 2 5 5 1 9 5
2,4- D 4 2

. 0 7 2 1 9 2 2 1 1 6 1

2,4- D B 5 5

. 5 3 1 6 1 1 6 3

A c i f l u orf e n 5 6

. 9 7 3 1 6 3 6 0 3 1 8

Ben t azon 3 7

. 0 2 2 3 9 2 4 0 2 4 1

Brom ox y n i l 4 5

. 9 5 2 7 6 2 7 8 2 7 4

C h l o rot h al on i l 6 2

. 6 5 2 4 5 2 4 7

C l opy ral i d 1 3

. 6 6 1 9 0 1 4 6 1 9 2

D act h a l

, m o n o aci d 4 2

. 0 8 2 7 3 2 7 1 2 7 5

D C A A 6 0

. 7 0 2 1 7 2 1 9

D i cam b a 2 8

. 5 9 1 7 5 1 7 7

D i ch l o r p r o p 4 5

. 8 9 2 3 3 2 3 5 1 6 1

D i n o s e b 6 2

. 1 7 2 3 9 2 4 0

MC PA 4 2

. 5 0 1 9 9 1 4 1 2 0 1

MC P B 5 5

. 8 9 1 4 1 1 4 3

Pi cl oram 1 9

. 7 3 2 4 1 2 3 9 1 9 5

T r i c l opy r 4 4

. 1 3 1 9 6 1 9 8 2 1 8

T a b l e 11. Autotune par am eter s f o r ac c eptable tuning c r iter ia us ed in this m e thod

[m /z, m a ss- to

- c h a rg e ratio ; am u , ato m ic m a ss u n it]

T u n e io n mass, m/z T a rg et p eak w i d t h

, amu (A) T u n i n g p a ram a ters f o r p o s itiv e io n m o d e 1 1 8

. 0 8 0

. 6 5

6 2 2

. 0 3

. 6 5

9 2 2

. 0 5

. 6 5

1

, 5 2 1

. 9 5

. 6 5

2

, 1 2 1

. 9 5

. 7 1 (B) T uni ng p a r a m e t e r s fo r ne ga t i v e i o n m o d e 1 1 2

. 9 9 0

. 6 5

6 0 1

. 9 8

. 6 5

1

, 0 3 3

. 9 9

. 6 5

1

, 6 3 3

. 9 5

. 6 5

2

, 2 3 3

. 9 1

. 7 4 

### The sig n a l inte nsity of the sy ste m is

f u r t he r optimize d by using the ion a t a ma ssto-charg e ratio of 622.03 as part of the autotune process. A compensated g a involtag e calibration curve is produced, and the

a

ppr opr ia te g a in a nd e l e c t r on multiplie r voltag e s produce a manufacturer-defined

minimum ion abundance of 5 x 10 4 

### to 1 x 10 6


### (m anufact urer’s arbi t r ary units). This process

is a u toma tic a nd is wr itte n to the a u totune f ile

. The autotune file also contains all the

pe r tine n t instr u me nt se tting s f o r

ma ss a x is calibration and peak width. F o r other

m a nufact urers’ HP L C / M S sy st em s, t h e

AN AL Y T I C AL M E T H O D 3 1

### appropriate ma nual or automated tuning procedure is used to meet instrument

spe c i f i c a tions f o r

c a libr a tion a nd minima l ion sig n al. Reg a rdless of the HPL C /MS sy stem used, electronic and pape r copies of tuning conditions should be stored chronolog ically to
monitor long

- t e r m HPL C /MS sy ste m

pe r f o r

m a n c e
, a ssist in de te r mining if maintenance or repairs are required, and allow

com p ari s on of sam p l e s anal y z ed over

ex tended (g reater than 6 months) periods.

The ma ss spe c t r o me te r perform ance needs t o m eet m a nufact urers' specifications for peak width, mass ax is, calibration, and minimum acceptable ion

si g n al i n t e nsi t y . I f i t does, proceed t o

c a libr a te qua ntita tive l y

. I f the pe r f o r

m a n c e is

not accept a bl e, however, t h en di ag nost i c
, prevent a t i v e or correct i v e procedures m i g ht be required. Manufacturer-supplied diag nostic procedures are used to identify and

correct any autotune-identified problems.

Fol l o wi ng any correct i ons, repeat t h e autotune procedure to verify that the

correct i ons resul t i n accept a bl e i n st rum e nt perform ance. W h en accept a bl e m a ss

spe c t r o me te r ma ss a x is a nd sig n a l inte nsity have been achieved, as indicated by a successful autotune, the instrument can be

c a libr a te d f o r

qua ntita tive a n a l y s is.

7.4.2.5.2 Quantitativ e

c a libration —A multiple c onc e n tr a tion

c a libr a tion f o r

qua ntita tive a n a l y s is is c a r r i e d out for all compounds after acceptable mass spectrometer tuning is completed. The seven

c onc e n tr a tions f o r

this c a libr a tion a r e liste d in

table 6 of section 5.4.6.3 and are the same for positive a nd ne g a tive ion a n a l y s is. The se ve n cal i b rat i on concent r at i ons are anal y z ed sequentially , and calib rat i on curves are

pr oduc e d. A minimum of f

our qua ntita tion

le ve ls must be use d to de te r mine the calibration curve, and the curve should have a

correl a t i on coeffi ci ent (r 2 

### ) g r eater than 0.995. Most compounds will ex hibit linear

cal i b rat i on curves wi t h accept a bl e r 2 

### values, but some analy t es (ty p ically atraz i ne, deethy latraz i ne, deisopropy latraz ine, deethy ldeisopropy latraz ine, a nd 2-hy drox y a traz ine)

r e quir e qua dr a tic c u r v e f itting to a c h ie ve accept a bl e r 2 

### values. I f one or two of the

cal i b rat i on curve st andard levels are not used, there must be a leg itimate reason for dropping

t h e poi nt from t h e curve, such as an

i n com p l e t e or i n accurat e i n j e ct i on or som e

e v ide n c e tha t sta nda r d solution qua lity ha s fal l e n bel o w accept a bl e l e vel s . C o rrect i v e actions, such as preparing new standards, also would be required. Note that two analy t es, 2- hy drox y a traz ine and deethy ldsisopropy latraz i ne, require separa te c a libr a tion c u r v e s

. A limite d se t of thr e e to f our c a libr a tion points is used because both compounds are alway s reported as es timates. This second

c a libr a tion is c a l c u la te d f o r

positive ion analy s is only

.

I f

the initial calibration is acceptable,

the se t( s) of e nvir onme n ta l sa mple s, se t qua lity

c ontr o l ( Q C) sa mple s, and instrument QC

sa mple s a r e c o mbine d into a ba tc h a nd analy z ed. A batch ty pically consists of up to six

e nvir onme n ta l sa mple se ts of 10 samples each,

the a ssoc i a t e d se t QC sa mple s, a nd instr u me nta l QC sa mple s to monitor pe r f o r

m a n c e

. Note tha t
anal y s i s of t h e ent i r e anal y t i cal bat c h can require up to a week or more of continuous instrument operation. As a result, QC data need to be reviewed during the analy s is of the

bat c h t o ensure accept a bl e i n st rum e nt operat i on throug hout the analy s is.

I n str u me nta l QC sa mple s a r e inte r s pe r s e d be twe e n environmental and set QC sam p l e s. The presence of i n t e rspersed

instr u me nta l QC sa mple s allows use of part of

the da ta c o lle c t e d in the ba tc h a n a l y s is in c a se of calibration problems or instr u me nt f a ilur e during the batch sequence. The first

instr u me nt QC sa mple ty pe use d to monitor batch performance is the continuing

c a libr a tion ve r i f i c a tion ( CCV) sa mple . The CCVs ensure ong oing acceptable calibration performance during analy s is of the batch.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 32

### W h en CCV results vary by more than 30

pe r c e n t, da ta a r e r e por te d a s e s tima te s; if the CCV results vary by more than 40 percent for five analy t es, a new calibration is required. A continuing calibration blank (CCB ) follows

each C C V , and i s used t o m oni t o r possi bl e cross-contamination betw een i n j ect i ons as a

r e sult of inc o mple te inje c tion or insuf f i c i e n t injection-needle washing

. Ty pical batch

a n a l y tic a l se que nc e s f o r

positive a nd ne g a tive ion analy s es are listed in table 12. Note that this sequence includes analy s es for producing a calibration curve. The sequence would be adj u st ed i f a cal i b rat i on curve was not required. Note also that the position of the

reag ent bl ank i n t h e preparat i on set i s vari ed

to monitor f

o r

position- spe c i f i c contamination. As a result, the position of the

se t r e a g e n t bla nk c a n va r y

within the

i n st rum e nt anal y t i cal sequence.

7.4.2.6 Evaluation of instrument

a n a l y s is r e sults

7.4.2.6.1 The QC and environmental sample da t a are revi ewed t o ensure that they m eet acceptance criteria upon

c o mple tion or pa r tia l c o mple tion of the

a n a l y s is of a

ba tc h ( p a r tia l c o mple tion in the

case of a CCV or CCB failure). These data

a r e r e vie w e d qua lita tive l y a nd qua ntita tive l y to ensure that (1) detected compounds are

c o r r e c tly ide n tif ie d, a nd ( 2 ) the qua ntif ie d

concent r at i ons are correct l y cal cul a t e d.

7.4.3 Qualitativ e determination— S e veral cri t e ri a are used t o determine that a compound identification is

qua lita tive l y c o r r e c t . Cor r e c t ide n tif ic a tion is

ba se d on ( 1 ) the time a t whic h the a p e x of the

chrom a t o g r aphi c peak el ut es from t h e HP L C

i n t o t h e MS , (2) t h e presence of up t o t h ree compound-specific ions in the selected-ion monitoring mass spectrum (table 10), and (3)

the relative abundances of these ions in the selected-ion monitoring sig n al and mass

spect ra. These cri t e ri a are det e rm i n ed from

anal y s i s of aut h ent i c st andards, and are

veri fi ed by anal y s i s of st andards i n each ba tc h, to c o mpe n sa te f o r

long

- t e r m c h a n g e s in

the HPL C /MS sy stem. Compounds are

qua lita tive l y de te c t e d whe n the f o llowing

cri t e ri a are m e t :

R e t e nt ion t i m e

— The inte nsitie s of

t h e charact eri s t i c i ons of a compound are at a max imum that

should coincide within ± 0.1

minute of the r e te ntion time of the selected compound. I n addition, the max ima of the primary (quantifi cation) ion and secondary and tertiary (qualification) ions should be

within 0.05 minute of each other.

Ma tr ix e f f e c t s a nd sa mple

- t osample pH variations can have a substantial influence on liquid

c h r o ma tog r a phic r e te ntion time s, the r e b y r e sulting in substa ntia l

variations of absolute retention time reproducibility , which also can be compound-dependent. An

a

b solute r e te ntion- time c r ite r i on i s t h erefore eval uat e d i n comparison to previously analy z ed standards and samples, and with cog n iz ance of known problems that can result in

r e te ntion- time va r i a tions.

Spe c t r a —The identity of each compound is verified by

com p ari n g t h e sel ect ed-i on monitoring spectrum of the suspected compound with a

reference sel ect ed-i on m oni t o ri ng spectrum obtained from a standard for that compound analy z ed in the same batch. Two

c r ite r i a a

pply

. F i r s t, the sa me two or three ions must be present in

t h e reference and sam p l e spect ra, althoug h there may be additional ions present if ions for additional compounds are collected

AN AL Y T I C AL M E T H O D 3 3T a b l e 12. T y pic a l m i nim u m s a m p le analy s is s equenc e f o r high- per f o r m anc e liquid c h r o m a togr aphy /m as s

s pec tr om etr y analy s is in this m e thod

[* , in d i cates q u ality

- c o n tro l sam p les an aly zed in p o s itiv e io n an aly s is o n ly ; μ g / L

, m i cro g ram p e r liter]

Inje c t ion numbe r Qua lity

- c ontr o l or e n v i r onme n ta l-s a m ple ty pe

1 Co n tin u i n g calib ratio n b l an k (u ltrap u r e so lv en t)

2 0.005 μg / L con cen t r at i o n s t an dard

3 0.01 μg / L con cen t r at i o n s t an dard

4 0.05 μg / L con cen t r at i o n s t an dard

5 0.10 μg / L con cen t r at i o n s t an dard

6 0.20 μg / L con cen t r at i o n s t an dard

7 0.50 μg / L con cen t r at i o n s t an dard

8 1.00 μg / L con cen t r at i o n s t an dard

9 0.05 μg /L con cen tration atrazin e

- d eg radate s t an dard*

10 0.20 μg /L con cen tration atrazin e

- d eg radate s t an dard*

11 0.50 μg /L con cen tration atrazin e

- d eg radate s t an dard*

12 1.00 μg /L con cen tration atrazin e

- d eg radate s t an dard*

1 3 Co n tin u i n g calib ratio n b l an k (u ltrap u r e so lv en t)

14 0.175 μg / L con cen t r at i o n t h i r d- part y ch eck s t an dard

1 5 En v i ro n m en tal sam p le- # 1

16 En v i ron m en t a l s a m p l e

- # 2

1 7 En v i ro n m en tal sam p le- # 3

1 8 En v i ro n m en tal sam p le- # 4

19 En v i ron m en t a l s a m p l e

- # 5

2 0 En v i ro n m en tal sam p le- # 6

2 1 En v i ro n m en tal sam p le- # 7

2 2 En v i ro n m en tal sam p le- # 8

2 3 En v i ro n m en tal sam p le- # 9

24 En v i ron m en t a l s a m p l e

- #10

25 Set qu ality con t rol s a m p le- #11 (ty p ically s e t reag en t blan k

, bu t can v a ry in s e qu en ce pos ition )

26 Set qu ality con t rol s a m p le- #12 (ty p ically s e t reag en t s p ik e)

2 7 0

. 2 0 μ g /L co n tin u i n g calib ratio n v e rif i catio n stan d a rd

28–39 T w elv e s e qu en ce en tries f o r en v i ro n m en tal/qu a lity con t rol s a m p les ( #13–#24)

4 0 0

. 2 0 μ g /L co n tin u i n g calib ratio n v e rif i catio n stan d a rd

4 1 Co n tin u i n g calib ratio n b l an k (u ltrap u r e so lv en t)

42–53 T w elv e s e qu en ce en tries f o r en v i ro n m en tal/qu a lity con t rol s a m p les (#25–#36)

5 4 0

. 2 0 μ g /L co n tin u i n g calib ratio n v e rif i catio n stan d a rd

55–66 T w elv e s e qu en ce en tries f o r en v i ro n m en tal/qu a lity con t rol s a m p les (#37–#48)

6 7 0

. 2 0 μ g /L co n tin u i n g calib ratio n v e rif i catio n stan d a rd

6 8 Co n tin u i n g calib ratio n b l an k (u ltrap u r e so lv en t)

69- 80 T w elv e s e qu en ce en tries f o r en v i ro n m en tal/qu a lity con t rol s a m p les (#49–#60)

8 1 0

. 2 0 μ g /L co n tin u i n g calib ratio n v e rif i catio n stan d a rd

82–93 T w elv e s e qu en ce en tries f o r en v i ro n m en tal/qu a lity con t rol s a m p les (#61–#72)

9 4 0

. 2 0 μ g /L co n tin u i n g calib ratio n v e rif i catio n stan d a rd

95 0.20 μg /L con cen tration atrazin e

- d eg radate s t an dard*

9 6 0

. 0 5 μ g /L lim it o f q u an titatio n stan d a rd

9 7 0

. 0 5 μ g /L lim it o f q u an titatio n atrazin e

- d eg rad a te stan d a rd *

9 8 Co n tin u i n g calib ratio n b l an k (u ltrap u r e so lv en t)

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 34

### concurrently . Second, the areas of

the s e ions, de te r mine d f

r o m i n t e g r at ed peak areas of m a ss

c h r o ma tog r a m s, must be within 20

pe r c e n t of the a b solute r a tios obtained on injection of a standard solution g e ne r a te d using the conditions of this method. Meeting

the s e c r ite r i a f

o r

qua lita tive

i d ent i f i cat i on requi res careful

consideration. One must determine

whether the abundances in the selected-ion profile s are appropriate and if the profile s have relative

inte nsitie s tha t a r e c onsiste nt with

t h e reference m a ss spect rum
, or i f

the r e a r e c ontr i butions to the r e la tive abundances resulting from

i n t e rference. Ex peri ence and

t r ai ni ng are necessary t o recog n i z e the salient features of individual mass spectra and potential

i n t e rferences. Ex erci se careful judg me nt in ma king a qua lita tive identification, g i ven the variability inherent in identify i ng compounds at

low concentrations in environmental

sa mple s.

7.4.4 Quantitativ e determinations

— W h en a compound is

qua lita tive l y de te r mine d to be pr e s e n t, a quantitative determina tion of the compound

concentration can then be made. The

concentration of that compound will be based

on t h e i n t e g r at ed area from t h e pri m a ry quantitation ion of that compound, the

r e g r e ssion line f itte d to the initia l c a libr a tion

curve, t h e area of t h e i n t e rnal st andard i n t h e sample, and the intern al standard response

f a c t or s r e la tive to the inte r n a l sta nda r d response factor from the calibration standards. This method ty pically uses linear-fitted

curves. F o r atraz i ne and the atraz i ne deg r adates measured in this method, a

qua dr a tic f itte d c u r v e is use d f

o r

mor e accurat e concent r at i on det e rm i n at i on across the method calibration rang e. I n practice, quadratic and linear cu rves provide equally

accept a bl e resul t s , and a quadrat i c curve can be used for all compounds if found to be more

pract i cal

.

7.4.5 Analysis of dilutions

— Sa mple s must be a n a l y z e d within the r a ng e of

the calibration curve. I n environmental samples, compound responses that ex ceed the response of the hig h est standard in the calibration curve, 1.0 μ g / L

, should be broug ht

within the r a ng e of the c a libr a tion c u r v e by diluting the e x tr a c t , using the initia l c a l c u la te d

c onc e n tr a tion a s a g u ide f o r

de te r mining the appropriate dilution volume, and then

reanal y z i n g

. For ex am pl e, an undi l u t e d

sa mple with a n initia l c a l c u la te d

concentration of 5.0  g / L could be diluted to 10 percent of its orig in al concentration, so a

pr e d ic te d c onc e n tr a tion of the dilute d e x tr a c t should be within the calibration rang e of the

method.

8. Calculations

I n this method, the calculation of a final concentration of a polar org a nic compound ( P OC) in a f

ilte r e d wa te r sa mple r e quir e s multiple c a l c u la tions, a s f o llows.

8.1 Calculate the relative response

fact ors for each P O C from t h e cal i b rat i on analy s es conducted in 7.4.2.5.2 by using a be st- f it line a r r e g r e ssi on or quadratic fit model. Rearrang e the equation of the linear

form y = mx + b to m = (y

- b )/

x a s f o llows:

RRF c 

### =

    



    

 

     

is c is c

amt amt b

area area



### (5)

AN AL Y T I C AL M E T H O D 3 5

### w h ere RRF c 

### = the relativ e response factor for the polar

org a nic com pound (P O C ) of interest;

area c 

### = the integ r ated peak area
of the P O C of interest;

area is 

### = the integ r ated peak area of the positiv e or

neg a tiv e ioniz a tion

internal standard used

for the P O C of interest;

amt c 

### = the m a ss of the POC of
interest, in nanog ram s ;

amt is 

### = the m a ss in nanog ram s
of the P O C internal standard (see section 5.4.5) used for the POC of interest; and

b = the y

- i ntercept of the

best- f it linear reg r ession

line.



### N O TE: A simila r c a l c u la tion c a n be ma de

f o r

f

itte d qua dr a tic c u r v e c a libr a tions by

rearrang ing the equation y = ax 2 

### + bx + c , where

a , b , and c are ex perimental constants

de te r mine d f

r o m the f itte d c u r v e by ite r a tive

ma the m a tic a l e x tr a c tion with c u r v e

- f itting

soft ware.

8.2 Calculate the volume of water

e x tr a c t e d, in lite r s ( V s ):

V

s = ( V i 

### – V f



### ) / 1,000 (6)

w h ere V i = initial w e ig ht of sam p le

and sam p le bottle, in

gr a m s (  m L ; 7.3.7);

V f = final weig ht of sam p le and

sam p le bottle, in g r am s (  m L ; 7.3.7); and

1,000 = conv ersion factor for

m illiliters to liters.



### N O TE: This procedure assumes that the volumetric density of a t y pi cal freshwat e r

sa mple is 1 g /mL . F o r sa mple s c o lle c t e d f

r o m saline environments, a salinity or density

determination should be made and a volume correction applied (see 7.3.7).

8.3 Calculate sample polar org a nic compound concentrations

I f

the compound of interest has met the

qua lita tive ide n tif ic a tion c r ite r i a liste d in 7.4.3, calculate the compound concentration

in the sa mple a s f o llows:

C

=      

s is c c is

V

A RRF A amt



### x x x (7)

w h ere C = the concentration of the

com pound of interest in

the sam p le, in m i crog ram s per liter;

amt is = the m a ss of internal standard

added to the sam p le, in

mi c r o g r a ms ;

A c = the area of the quantitation

ion for the com pound of interest;

RRF c = the relativ e response factor

for the com pound of interest,

calculated abov e in 8.1;

A is = the area of the quantitation

ion for the internal standard; and

V

s 

### = the v o lum e of sam p le extracted,

in liters, calculated in 8.2 (equation 6).



### 8.4 Calculate the percentag e recovery of the surrog a te compounds in each sample by using

R a =    

s V a V a C C s / ) ( x 

### x 100 (8)

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 36

### w h ere R a = recov e ry of surrog a te in

sam p le, in percent;

C

s = concentration of surrog a te

in sam p le, in m i crog ram s per liter, calculated by using equation 7;

C

a = concentration of com pound
in the surrog ate solution

added to the sam p le, in

m i crog ram s per m i croliter (5.4.3);

V

a = v o lum e of POC surrog ate

solution added to the sam p le,

ty

pically 100 μ L (7.3.1); and

V

s = v o lum e of sam p le, in liters
(calculated in 8.2).



### 8.5 Calculate the percentag e recovery of compounds in set reag ent spike sample by using

R 

### b =  

   

s b b s
V V C C

/ ) ( 

### x x 100 (9)

w h ere R b = recov e ry of fortified com pound

in the set P O C fortification

sam p le, in percent;

C

s = concentration of com pound in

set reag ent spik e sam p le, in

m i crog ram s per liter, calculated using equation 7;

C b = concentration of com pound in

reag ent spik e fortification

solution added to sam p le, in

m i crog ram s per m i croliter (5.4.4);

V

b = v o lum e of reag ent spik e

fortification solution added

to the sam p le, ty pically

100 μ L (7.3.2); and

V

s = S e t reag ent spik e sam p le v o lum e
, in liters (calculated in 8.2). 

### 9. Reporting of Results

9.1 Reporting units— Report compound concentrations for field samples in microg r ams per liter. Report compound

c onc e n tr a tions f o r

f

i e l d sa mple s to 4 de c ima l pl aces, but no m o re t h an 3 si g n i f i cant fi g u res. Report data for compounds reported as qualified estimates to 4 decimal places, but no

mor e tha n 2 sig n if ic a n t f i g u r e s. Re por t

surrog a t e dat a for each sam p l e t y pe as percent recovered, and report t o 1 deci m a l pl ace (tenths of a percent), but no more than 3 sig n if ic a n t f i g u r e s. Re por t da ta f

o r

the se t
f o r tif ic a tion sa mple a s percent recovered, and

report t o 1 deci m a l pl ace (t ent h s of a percent )

, but no more than 3 sig n ificant fig u res. Compounds quantified in the set blank sample

a r e r e por te d in mic r o g r a m s pe r lite r
, a nd a r e report e d t o 4 deci m a l pl aces, but no m o re t h an 3 sig n if ic a n t f i g u r e s.

9.2 Reporting limits and levels

— Method detection limits (MDL s) that use the

pr oc e dur e s outline d by the U.S. Environmental Protection Ag ency (1997)

have been calculated for this method and are

discussed further in section 11.8. The interim

l a

borat ory report i n g l e vel (L R L ) for each compound determined using this method is

cal cul a t e d accordi n g t o C h i l d ress and ot hers (1999) and is twice the method detection

limit. Re por t qua lita tive l y ide n tif ie d compound concentrations (those POCs that

a r e ide n tif ie d f r o m r e la tive r e te ntion time a nd MS spe c t r a l f it) tha t a r e le ss tha n the MDL or le ss tha n the lowe st c a libr a tion sta nda r d a s estimated concentrations. Compounds that

are not det ect ed are report e d as l e ss t h an t h e inte r im L R L

.

10. Qualit y A ssurance/Qualit y Cont rol

L a borat ory ex t r act i on sam p l e s are form ed i n t o set s , each consi s t i n g of 10

e nvir onme n ta l sa mple s, a se t r e a g e n t spike and set reag ent blank, for a total of 12

AN AL Y T I C AL M E T H O D 3 7

### samples. F i eld equipment blanks and

la

bor a t or y

ma tr ix spik es, whose frequency is determined by the method user, provide

a dditiona l qua lity a ssur a nc e / qua lity c ontr o l (QA/QC). The frequency of anal y s i s of t h ese QA/ QC sam p l e s and t h e aspect s of t h e anal y t i cal process t h ey m oni t o r are descri bed.

10.1 Surrogate . Surrog a tes are org a nic compounds that are placed into all filtered

wa te r sa mple s pr ior to e x tr a c tion on the SPE

cart r i d g e . S u rrog a t e s are ex pect ed t o behave similarly to selected compounds for SPE

recovery and are not ex pected to be present in

t h e envi ronm ent

. Three surrog a t e s are used i n this method, two ( 13 

### C

- caffei n e and Barban) for compounds determined under positive

ioniz a tion conditions, and one (2,4,5-T), for compounds determined under neg a tive

ioniz a tion conditions. The herbicide 2,4,5-T had been previously used as a pesticide, althoug h reg i strations for all uses in the

Uni t e d S t at es have been cancel ed si nce 2

J a nuary 1985 (U.S. Environmental Protection Ag ency , 2000). I n 12,064 surface- and

g r ound-water samples, 2,4,5-T was detected 68 times using a similar analy tical method (W erner and others, 1996) Given the limited number of appropriate neg a tive ioniz a tion

surrog a tes, 2,4,5-T was used as a surrog a te
because t h e frequency of envi ronm ent a l

presence was very low, and the frequency of

de te c tions in the f u tur e is like l y to de c r e a s e furt her.

Ex amination of surrog a te recovery for individual samples pr ovide s insig h t into overall method performance for that particular

sa mple . Contr o l limits, de te r mine d by using

st at i s t i cal process cont rol techniques and an

ex tended sequence of laboratory reag ent spike and reag ent bl ank surrog a t e recoveri es, are used to evaluate surrog a te recoveries of individual samples.

10.2 Laboratory reagent spike ( L RS)

. A 1- L or g a nic

- f r e e wa te r sa mple is f o r tif ie d a t

0.25 μ g / L for all compounds determined in this method. This sample then is included wi t h each sam p l e set and i s carri ed t h roug h

the entire ex traction, el ution, and analy tical procedure. The L R S recoveries reflect method performance in the absence of any

e nvir onme n ta l sa mple ma tr ix . The s e r e sults

a r e use d to de te r mine if ove r a ll se t r e c ove r i e s are accept a bl e, or i f t h ere was a g r oss chang e in method performance in the set. Acceptability is defined from analy s is of a

series of L R S samples, ty pically 30 or more,

pr oc e sse d by multiple ope r a tor s , who use d

different instruments. S t at i s t i cal process

c ontr o l a n a l y s is is use d with the s e da ta to
devel op accept a nce cri t e ri a.

10.3 Laboratory reagent blank ( L RB)

. A 1- L or g a nic

- f r e e wa te r sa mple is f o r tif ie d with method surrog a tes only

. One L R B is

i n cl uded wi t h each sam p l e set and i s carri ed throug h the entire ex traction, elution, and analy s is procedure. The L R B is used to monitor for impurities and contamination, and, because it follows the L R S in the sample instrumental analy s is sequence, it also

m oni t o rs for carry over bet w een sam p l e inje c tions.

10.4 Continuing c a libration v e r ific ation ( CCV)

. F o r each analy s is ty pe (positive

ioniz a tion or neg a tive ioniz a tion), a 0.25- μ g/ L

calibration standard that contains all of the selected compounds, including surrog a tes and

inte r n a l sta nda r d s, is inse r t e d in a n

aut o sam p l e r vi al and pl aced bet w een every 12

environmental and se t QA/QC sa mple s throug hout the HPL C /MS analy s is. These

C C V sam p l e s are used t o ensure t h at t h e

c a libr a tion of the HPL C /MS sy ste m is within
acceptable limits, ty pically  30 percent. I f

the c ontr o l limits a r e e x c e e d e d, e nvir onme n ta l

sam p l e s t h at fol l o w t h e l a st accept a bl e C C V

a r e r e a n a l y z e d. Contr o l limits f o r

the CCV

rarel y were ex ceeded duri n g t h e course of t h i s study

.

10.5 Continuing calibration blank ( CCB) . A sample of org a nic-free water is

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 38

### pl aced i n an aut o sam p l e r vi al behi nd a C C V

, with a ty pical frequency of one every third set of samples. The CCB follows the CCV, and

thus monitor s f o r

pote n tia l inje c tion- toinje c tion c a r r y ove r
, a s we ll a s instr u me nta l

contamination.

10.6 Limit-of-quantitation ( L OQ)

standard . The L OQ standard is an aliquot of

the lowe st c onc e n tr a tion c a libr a tion solution used to develop the calibration curve (ty p ically 0.005 μg /L ; see section 5.4.6.3).

The L OQ i s anal y z ed at t h e end of a sam p l e anal y t i cal sequence t o veri fy t h at suffi ci ent
instr u me nt se nsitivity ha s be e n ma inta ine d throug hout the sequence.

10.7 Field equipment blank ( FEB) . A volume of org a nic-free water is processed

e x a c tly a s e nvir onme n ta l sa mple s by using a ll appropriate on-site sa mpling equipment and

te c hnique s. This pr oc e ss inc l ude s bottle s,

c o mpositing

, splitting

, a nd f ilte r i ng . The F E B

i s processed at t h e st ar t of sa mpling a nd the n about every 15 to 20 samples. The F E B monitors for contamination or carry over, or both, r e sulting f r o m f i e l d sa mpling a nd equipment cleaning techniques that could cause equipment contamination of

e nvir onme n ta l sa mple s.

10.8 Fie l d matrix spik e ( F

M S

) . The

F M S is a duplic a t e e nvir onme n ta l sa mple tha t
is fortified at 0.25 μ g / L for all compounds

determined in this method. The unfortified duplic a t e is use d to de te r mine na tur a lly present concentrations of any compounds measured in the sample. I f concentrations of method compounds are determined, they are subt ract ed from t h e m easured concent r at i ons in the f o r tif ie d sa mple . The c o r r e c t e d recoveries of method compounds are determined from the backg r ound

concentration-subtracted results. The F M S

me a s ur e s the e f f e c t s of the sa mple ma tr ix on the recovery of met hod compounds. Several

effect s are possi bl e, i n cl udi ng m a t r i x

enhanced compound deg r adation, matrix

introduced coeluting interferences, and matrix enhancement of compound concentration. The frequency of F M S

a n a l y s e s is de te r mine d by da ta

- qua lity objectives.

11. Method Performance

This method was orig inally developed as a custom analy tical method by the USGS and was put into routine use in J une 1999 at

the NWQL . As pa r t of the initia l c u stom method testing

, compound recovery was determined in J une 1999 in three water ty pes
at a fortified concentration of 0.100  g/ L

. The three matrices we re laboratory

- produced, pesticide-free, org a nic-free water; a g r oundwa te r sa mple f r o m a pr iva t e dome s tic we ll;

and a surface-wat er sam p l e col l ect ed from t h e South Platte River in Denver, Colorado. The surface- and g r ound-wa ter samples were

col l e ct ed fol l o wi ng t h e precaut i ons sug g e st ed in Shelton (1994) for avoiding sample

contamination.

Upon acceptance of these results, the method was applied to surface- and g r oundwa te r sa mple s c o lle c t e d a c r oss the Unite d

States from March 1999 to J u ly 2000.

Additional method valid ation samples were analy z ed in F e bruary 2000 using the same

wa te r ty pe s a nd f o r tif ie d a t nomina l

concentrations of 0.025 and 0.50  g/ L d u r i n g this period when the method was being used

rout i n el y for cust om anal y s i s . One compound, dichlorprop, which was not present in the initial 0.100 fortifications, was

a dde d to the spiking solutions a f te r a

suita ble

standard was obtained. The combined performance studies at fortifications of 0.025,
0.100, and 0.50  g / L are used t o eval uat e method performance. Provisional MDL s were determined using the initial org a nic-free
water data, fortified at 0.100  g / L. La t e r
MDL de te r mina tions we r e ma de using the

resul t s from org a ni c-free wat e r fort i f i e d at

0.025  g / L for org a nic-free water and g r ound
water, and at 0.050  g / L for surface wat e r.

AN AL Y T I C AL M E T H O D 3 9

### As of J u ly2000, about 3,300 surfaceand g r ound-water samples were analy z ed with this method. The results for set quality

control samples (197 laboratory reag ent blanks and 285 laboratory reag ent spikes)

were anal y z ed concurrent l y wi t h t h ese

e nvir onme n ta l sa mple s, ag g r eg at ed, and t h e da ta e v a l ua te d f o r

long

- t e r m ( m ultiple instrument, multiple operator) method perform ance.

11.1 Recoveries from fortified water

sa mple s

11.1.1 The performance of this

method for the ex traction and analy s is of POCs was evaluated by adding aliquots of

sta nda r d solutions to a minimum of six wa te r

sa mple s a nd pr oc e ssing the f o r tif ie d sa mple s throug h the entire method. Two unfortified

wat e r sam p l e s were processed wi t h each set

of

f

o r tif ie d sa mple s to de te r mine the concentrations of any POCs present in the

wa te r pr ior to spiking

. Re a g e n t spike s a nd unfortified laboratory r eag ent bl ank sam p l e s al so were processed wi t h each set

. Three

water ty pes were used for evaluating method performance and are described below.

11.1.2 The g r ound-water sample

wa s c o lle c t e d f

r o m a sing le

- f a mily dome s tic supply well near Everg r een, Colorado. W a ter
was col l ect ed from t h e wel l aft e r a sust ai ned

pe r i od of dome s tic use to minimize c ontr i

butions of water that had been stored in a lined pressuriz a tion tank. The well penetrates 85 m into a fractured rock aquifer with

minima l ove r l y i ng soil. This we ll wa s pa r t of a cooperative U.S. Geolog ical Survey

J e fferson County

, Colorado, g r ound-water monitoring prog ram near Everg r een, Colorado (Schwartz

, 1997). W a ter was
col l ect ed i n t o a precl eaned, 40-L st ai nl essste e l c onta i ne r a nd f ilte r e d in the la bor a t or y using the procedure de scribed in Sandstrom (1995). Samples were collected sequentially

into individua l, pr e

- a s he d 1- L a m be r bottle s for anal y s i s . W a t e r was col l ect ed several

time s f r o m this site ove r the c our se of the study . Dissolved org a nic carbon (DOC) was

not measured each time a water sample was

c o lle c t e d a t this site ; inste a d, DOC

concent r at i ons were m eas ured as part of the

g r ound-water monitoring prog ram described by Schwartz (1997).

11.1.3 The surface-water samples

were collected from the South Platte River as it pa sse s thr oug h me tr opolita n De nve r
, Colorado. The water quality of the South

Platte River has been ex tensively studied;

L itke and Kimbroug h (1998) provide an overview. Grab samp les of South Platte

R i ver wat e r were col l ect ed i n st ai nl ess-st eel

containers of either 10- or 40-L capacity that had been washed with soap and water and

se que ntia lly r i nse d with wa te r a nd solve n t.
The wa te r sa mple s we r e f ilte r e d using the procedure described in Sandstrom (1995), and split into individual 1-L aliquots in pre-ashed

1- L a m be r bottle s f o r

a n a l y s is. Ove r the course of the study , water was collected

se ve r a l time s f r o m two site s, one upstr e a m and one downstream of Denver. The DOC

concentrations were not measured on the individual samples used in this study . Median

DOC concentrations for the South Platte River from 1993–1995 were 5.2 mg /L at Denver and 7.0 mg /L at Henderson, Colorado, on the basis of measurements made as part of

the Sur v e y ' s Na tiona l Wa te r

- Q ua lity Assessment (NAW QA) prog ram. These data

a r e summa r i ze d in L itke a nd Kimbr oug h (1998).

11.1.4 The pesticide-free, org a nicfree wat e r was produced at t h e NW QL usi n g a Solution 2000 water purification sy stem (Model 2002AL

, Solution Consultants, I n c., J a sper, Ga.). The following method was used.

L a boratory

- distilled wa ter was introduced

into a 1- μ m activated carbon prefilter, passed throug h a series of ion ex chang e resin beds to

r e move dissolve d inor g a nic c onstitue n ts, followed by hig h -intensity UV radiation

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 40

### ox idation to remove dissolved org a nic carbon, and then filtered throug h a 0.22- μ m ste r ile filter. The org a nic-fr ee water was dispensed into pr e

- a s he d 1- L a m be r bottle s f o r

a n a l y s is.

This wa te r a l so wa s use d f

o r

e x tr a c tion se t QC sam p l e s (l aborat ory reag ent spi k es and blanks). I n these water samples, DOC was not determined, but routine monitoring of DOC in the water produced by this sy stem did

not detect DOC concentr ations at the long

term method detecti on level of 0.016 mg /L

.

11.2 Org a nic-free water fortification

recovery resul t s

11.2.1 Sets of 10 samples of

org a ni c-free wat e r were fort i f i e d wi t h a laboratory reag ent spike solution (5.4.4) at concentrations of 0.025, 0.100, and 0.500

 g / L

. The results are listed in tables 13 to 18. The mean, median, and th e standard deviation of recovery for all compounds in the tables

we r e c a l c u la te d f r o m the da ta f

o r

me a n recoveries of individual compounds. No method compounds were detected in unspiked

reag ent wat e r.

11.2.2 The mean positive

ioniz a tion recovery results for compounds reported without qualif ication (tables 13, 15,
and 17) were 103.5  11.5, 92  10.4, and

93.1  9.0 percent at fortifications of 0.025,
0.100, and 0.500  g / L

, respect i v el y

. The

me dia n r e c ove r i e s we r e simila r to the me a n s, 99.5, 88.0, and 93.0 percent, respectively

. The

me a n positive ioniza tion r e c ove r y

r e sults f o r compounds reported as qualified estimates were 87.9 ± 31.6, 89.3 ± 42.3, and 82.0 ± 26.1 percent at fortifications of 0.025, 0.100, and

0.500  g / L

, respect i v el y

. The m e di an

r e c ove r i e s f o r

qua lif ie d e s tima te s a l so we r e similar, at 94.0, 88.0, and 88.5 percent,

respect i v el y

.

11.2.3 Mean recoveries for compounds determined by neg a tive ioniz a tion and reported without qua lification (tables 14, 16, and 18) averag ed slig htly less than the positive ioniz a tion results, and were 76.9  5.4,

84.7  6.4, and 75.8  17.4 percent, at
fortifications of 0.025, 0.100, and 0.500  g/ L

, respectively

. The corresponding median recoveries were similar to the means, at 78.0, 85.0, and 78.0 percent, respectively

. F o r

neg a tive ioniz a tion compounds reported as

qua lif ie d e s tima te s, me a n r e c ove r i e s de c r e a s e d
and were more variable, at 64.6  10.7, 59.2  27.5, and 64.4  39.8 percent, respectively

, with corresponding median recoveries of 65.0, 69.0, and 62 percent.

11.2.4 Averag e recoveries of all compounds reported wit hout qualification at

all three fortification levels varied about  10.3 percent for compounds determined by positive

ioniz a tion and  9.7 percent for compounds determined by neg a tive ioniz a tion. This

resul t

, however, does not refl ect t h e anal y t i cal precision, which is better reflected by the

relative standard devi ation of individual compound recoveries in org a nic-free water, particularly those that are reported without quantitation qualifica tion. Under positive

ioniz a tion conditions, the mean relative

standard deviations for compounds reported without qualification in org a nic-free water

were 8.9  4.8, 11  3.4, and 6.3  3.6 percent for 0.025-, 0.100-, and 0.500- μ g / L f o r tif ic a

tions, respectively

. The corresponding

relative standard devi ations for neg a tive

ioniz a tion results reported without qualification were 10.4  3.7, 13.1  3.6, and 13.5  10.5 percent for 0.025-, 0.100-, and 0.500-

μ g / L f o r tif ic a tions, r e spe c tive l y

.

11.3 Ground-water fo rtification

recovery resul t s

11.3.1 Sets of 10 individual

g r ound-water samples we re fortified at
concentrations of 0.025, 0.100, and 0.500  g/ L (tables 19 throug h 24). The mean, median, and

the standard deviation of recovery for all compounds in the tables were calculated

AN AL Y T I C AL M E T H O D 4 1T a b l e 13. Ac c u r a c y and pr ec is ion data f r om 10 deter m i nations of the m e thod c o m pounds f o r t if ied

at 0.025 m i c r ogr am per liter in or ganic

- f r ee w a ter

, under pos itive ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit (μg/L)

2,4- D m e t h y l es t e r N 0.0279 0.00136 5 111 0.0043

2- H y drox y a t r azi n e Y

. 0 2 4 1

. 0 0 1 2 6 5 9 6

. 0 0 4 0 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .0283 .00382 14 113 .0121

3- H y drox y carbof u

r an N

. 0 2 3 6

. 0 0 0 9 2 4 9 4

. 0 0 2 9

3- K e t o carbof u

r an Y

. 0 1 5 6

. 0 0 2 2 4 1 4 6 2

. 0 0 7 1

A l di c a r b Y

. 0 2 3 3

. 0 0 6 2 5 2 7 9 3

. 0 1 9 8

A l di carb s u l f on e Y .0227 .00309 14 91 .0098

A l di carb s u l f ox i d e Y .0231 .00130 6 92 .0041

A t razi n e N

. 0 2 4 3

. 0 0 1 4 3 6 9 7

. 0 0 4 5

Ben d i o c a r b N

. 0 2 3 5

. 0 0 3 9 8 1 7 9 4

. 0 1 2 6

Ben o m y l N

. 0 2 4 0

. 0 0 0 6 0 2 9 6

. 0 0 1 9

Ben s u l f u

ron

- m e t h y l N

. 0 3 2 4

. 0 0 2 5 1 8 1 3 0

. 0 0 7 9

Brom aci l Y

. 0 2 6 5

. 0 0 5 1 4 1 9 1 0 6

. 0 1 6 3

C a f f e i n e N

. 0 2 3 6

. 0 0 1 5 0 6 9 5

. 0 0 4 8

C a rbary l N

. 0 2 7 4

. 0 0 4 4 7 1 6 1 1 0

. 0 1 4 2

C a rbof u

r an N

. 0 2 3 5

. 0 0 0 9 0 4 9 4

. 0 0 2 8

C h l o ram b en m e t h y l es t e r Y .0130 .00282 22 52 .0089

C h l o ri m u

ron

- et h y l N

. 0 2 9 3

. 0 0 1 5 3 5 1 1 7

. 0 0 4 8

C y cl oat e Y

. 0 2 2 0

. 0 0 2 0 6 9 8 8

. 0 0 6 5

D eet h y l a t r azi n e Y

. 0 2 8 8

. 0 0 4 4 4 1 5 1 1 5

. 0 1 4 1

D eet h y l d ei s opropy l a t r azi n e Y

. 0 4 3 6

. 0 0 7 0 2 1 6 1 7 5

. 0 2 2 2

D e i s opropy l a t r azi n e Y

. 0 2 4 1

. 0 0 1 6 4 7 9 6

. 0 0 5 2

D i ph en am i d N

. 0 2 2 0

. 0 0 4 1 8 1 9 8 8

. 0 1 3 2

D i u r on N

. 0 2 5 3

. 0 0 2 3 5 9 1 0 1

. 0 0 7 5

F e n u

r on N

. 0 2 7 5

. 0 0 4 9 8 1 8 1 1 0

. 0 1 5 8

F l u m et s u l a m Y

. 0 2 4 2

. 0 0 1 8 0 7 9 7

. 0 0 5 7

F l u o m e t u

ron N

. 0 2 8 2

. 0 0 4 8 8 1 7 1 1 3

. 0 1 5 5

Im azaqu i n Y

. 0 2 3 6

. 0 0 2 4 7 1 0 9 4

. 0 0 7 8

Im azeth a py

r Y

. 0 2 4 4

. 0 0 2 6 5 1 1 9 8

. 0 0 8 4

Im i d i c l opri d N

. 0 2 4 2

. 0 0 1 0 7 4 9 7

. 0 0 3 4

L i n u

r on N

. 0 2 7 7

. 0 0 2 2 8 8 1 1 1

. 0 0 7 2

M e t a l a x y l N

. 0 2 4 1

. 0 0 3 1 5 1 3 9 6

. 0 1 0 0

M e t h i o c a r b Y

. 0 2 4 2

. 0 0 1 2 7 5 9 7

. 0 0 4 0

M e t h om y l Y

. 0 2 3 4

. 0 0 0 7 1 3 9 4

. 0 0 2 2

M e t h om y l ox i m e Y .0088 .00166 19 35 .0053

M e t s u l f u

ron

- m e t h y l Y

. 0 2 3 7

. 0 0 3 8 7 1 6 9 5

. 0 1 2 3

N e bu ron N

. 0 2 5 1

. 0 0 1 8 9 8 1 0 1

. 0 0 6 0

N i cos u l f u

r on N

. 0 2 4 4

. 0 0 2 0 5 8 9 8

. 0 0 6 5

N o rf l u

razon Y

. 0 2 6 3

. 0 0 2 5 9 1 0 1 0 5

. 0 0 8 2

O r y zal i n N

. 0 2 9 9

. 0 0 2 7 7 9 1 2 0

. 0 0 8 8

O x am y l N

. 0 2 2 2

. 0 0 1 9 4 9 8 9

. 0 0 6 1

O x am y l ox i m e Y .0070 .00211 30 28 .0067 Proph am N

. 0 2 6 0

. 0 0 1 5 3 6 1 0 4

. 0 0 4 8 Propi con azol e N

. 0 3 1 8

. 0 0 3 3 2 1 0 1 2 7

. 0 1 0 5 Propox u r N

. 0 2 2 3

. 0 0 1 2 7 6 8 9

. 0 0 4 0

S i du ron N

. 0 2 8 3

. 0 0 2 6 6 9 1 1 3

. 0 0 8 4

S u l f om et u

r on

- m et h y l N

. 0 2 3 3

. 0 0 1 4 0 6 9 3

. 0 0 4 4

T e bu t h i u ron N

. 0 2 4 1

. 0 0 0 9 8 4 9 7

. 0 0 3 1

T e rbaci l Y

. 0 2 3 1

. 0 0 1 5 6 7 9 2

. 0 0 4 9

T r i b en u

r on

- m et h y l Y

. 0 0 7 9

. 0 0 1 4 0 1 8 3 2

. 0 0 4 4

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 42Ta b l e 14 . Ac c u r a c y and pr ec is ion data f r om 10 deter m i nations of the m e thod c o m pounds f o r t if ied

at 0.025 m i c r ogr am per liter in or ganic

- f r ee w a ter

, under negative ioniz a tion

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit (μg/L)

2,4- D N 0

. 0 2 3 9 0

. 0 0 3 3 4 1 4 9 6 0

. 0 1 0 9 2,4- D B Y

. 0 2 0 7

. 0 0 2 4 5 1 2 8 3

. 0 0 8 0

A c i f l u orf e n N

. 0 2 3 2

. 0 0 1 0 1 4 9 3

. 0 0 3 3

Ben t azon Y

. 0 1 5 3

. 0 0 1 7 0 1 1 6 1

. 0 0 5 5

Brom ox y n i l Y

. 0 1 5 1

. 0 0 2 6 0 1 7 6 0

. 0 0 8 5

C h l o rot h al on i l Y

. 0 1 4 7

. 0 0 5 3 1 3 6 5 9

. 0 1 7 3

C l opy ral i d N

. 0 2 5 8

. 0 0 2 1 3 8 1 0 3

. 0 0 6 9

D act h a l m o n o aci d N .0257 .00179 7 103 .0058

D i cam b a N

. 0 2 4 4

. 0 0 1 9 7 8 9 7

. 0 0 6 4

D i ch l o r p r o p N

. 0 2 5 8

. 0 0 2 1 3 8 1 0 3

. 0 0 6 9

D i n o s e b N

. 0 0 6 4

. 0 0 1 8 4 2 9 2 6

. 0 0 6 0

M C PA N

. 0 2 3 0

. 0 0 2 5 0 1 1 9 2

. 0 0 8 1

M C P B Y

. 0 1 9 4

. 0 0 2 3 6 1 2 7 8

. 0 0 7 7

Pi cl oram N

. 0 2 3 0

. 0 0 3 0 3 1 3 9 2

. 0 0 9 9

T r i c l opy r N

. 0 2 4 9

. 0 0 3 4 4 1 4 1 0 0

. 0 1 1 2

T a b l e 15. Ac c u r a c y and pr ec is ion data f r om s e ven deter m i nations of the m e thod c o m pounds f o r t if ied at

0.10 m i c r ogr am per liter in or ganic

- f r ee w a ter

, under pos itive ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D m e t h y l es t e r N 0.0800 0.01376 17 80

2- H y drox y a t r azi n e Y

. 1 1 3 1

. 0 3 0 6 5 2 7 1 1 3 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .1003 .01455 15 100

3- H y drox y carbof u

r an N

. 0 9 2 4

. 0 0 9 9 1 1 1 9 2

3- K e t o carbof u

r an Y

. 0 8 2 2

. 0 1 1 5 0 1 4 8 2

A l di c a r b Y

. 0 6 1 9

. 0 1 2 9 7 2 1 6 2

A l di carb s u l f on e Y .0672 .02544 38 67

A l di carb s u l f ox i d e Y .0765 .00431 6 77

A t razi n e N

. 0 9 4 0

. 0 1 1 7 2 1 2 9 4

Ben d i o c a r b N

. 0 8 6 0

. 0 0 9 7 3 1 1 8 6

Ben o m y l N

. 0 8 2 0

. 0 0 3 4 9 4 8 2

Ben s u l f u

ron

- m e t h y l N

. 0 9 3 9

. 0 0 7 6 7 8 9 4

Brom aci l Y

. 0 9 4 4

. 0 1 2 8 3 1 4 9 4

C a f f e i n e N

. 1 0 9 4

. 0 1 2 8 0 1 2 1 0 9

C a rbary l N

. 0 8 8 5

. 0 0 9 9 9 1 1 8 9

C a rbof u

r an N

. 0 8 5 0

. 0 0 9 0 1 1 1 8 5

C h l o ram b en m e t h y l es t e r Y .0939 .01812 19 94

C h l o ri m u

ron

- et h y l N

. 0 8 6 4

. 0 0 5 8 4 7 8 6

C y cl oat e Y

. 0 7 2 0

. 0 0 8 6 4 1 2 7 2

D eet h y l a t r azi n e Y

. 1 0 8 9

. 0 1 3 8 1 1 3 1 0 9

D eet h y l d ei opropy l a t r azi n e Y

. 0 8 8 2

. 0 0 9 5 3 1 1 8 8

D e i s opropy l a t r azi n e Y

. 1 0 6 3

. 0 1 1 7 3 1 1 1 0 6

D i ph en am i d N

. 0 8 4 7

. 0 0 9 2 5 1 1 8 5

D i u r on N

. 0 9 1 8

. 0 1 2 6 2 1 4 9 2

F e n u

r on N

. 0 8 6 3

. 0 1 1 6 9 1 4 8 6

F l u m et s u l a m Y

. 1 3 4 1

. 0 1 3 7 7 1 0 1 3 4

AN AL Y T I C AL M E T H O D 4 3T a b l e 15. Ac c u r a c y and pr ec is ion data f r om s e ven deter m i nations of the m e thod c o m pounds f o r t if ied at

0.10 m i c r ogr am per liter in or ganic

- f r ee w a te r

, under pos itive ioniz a tion c onditions —Continued

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

F l u o m e t u ron N 0

. 0 8 7 3 0

. 0 0 9 8 2 1 1 8 7

Im azaqu i n Y

. 1 6 6 4

. 0 1 6 3 9 1 0 1 6 6

Im azeth a py r Y

. 2 0 0 7

. 0 1 3 9 9 7 2 0 1

Im i d i c l opri d N

. 0 9 8 7

. 0 1 6 8 8 1 7 9 9

L i n u r on N

. 0 8 7 2

. 0 1 1 0 5 1 3 8 7

Met a l a x y l N

. 0 8 4 0

. 0 0 9 0 9 1 1 8 4

Met h i o c a r b Y

. 0 8 8 4

. 0 1 2 6 5 1 4 8 8

Met h om y l Y

. 0 8 1 0

. 0 1 2 2 2 1 5 8 1

Met h om y l ox i m e Y .0121 .00162 13 12

Met s u l f u ron

- m e t h y l Y

. 0 7 5 9

. 0 1 8 1 0 2 4 7 6

N e bu ron N

. 0 9 0 1

. 0 1 1 8 8 1 3 9 0

N i cos u l f u r on N

. 1 2 9 5

. 0 1 0 3 9 8 1 3 0

N o rf l u razon Y

. 0 9 2 5

. 0 1 2 3 2 1 3 9 3

O r y zal i n N

. 0 8 7 4

. 0 1 1 3 1 1 3 8 7

O x am y l N

. 0 8 3 6

. 0 0 2 5 5 3 8 4

O x am y l ox i m e Y .0259 .01025 40 26 Proph am N

. 0 8 4 3

. 0 1 1 4 1 1 4 8 4 Propi con azol e N

. 1 0 0 0

. 0 1 0 2 4 1 0 1 0 0 Propox u r N

. 0 8 5 4

. 0 0 9 4 5 1 1 8 5

S i du ron N

. 0 9 6 0

. 0 1 4 8 4 1 5 9 6

S u l f om et u r on

- m et h y l N

. 0 9 8 2

. 0 0 6 1 8 6 9 8

T e bu t h i u ron N

. 1 0 6 2

. 0 1 2 2 0 1 1 1 0 6

T e rbaci l Y

. 0 9 6 6

. 0 1 5 1 7 1 6 9 7

T r i b en u r on

- m et h y l Y

. 0 2 6 8

. 0 1 0 7 8 4 0 2 7

T a b l e 16. Ac c u r a c y and pr ec is ion data f r om s e ven deter m i nations of the m e thod c o m pounds f o r t if ied at

0.10 m i c r ogr am per liter in or ganic

- f r ee w a ter

, under negative ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter; n d , n o t d e term in ed ]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D N 0

. 0 7 2 2 0

. 0 1 2 3 1 1 7 7 2 2,4- D B Y

. 0 7 0 5

. 0 0 8 5 6 1 2 7 1

A c i f l u orf e n N

. 0 8 4 7

. 0 0 9 9 0 1 2 8 5

Ben t azon Y

. 0 6 1 2

. 0 0 3 0 7 5 6 1

Brom ox y n i l Y

. 0 8 2 7

. 0 0 9 0 9 1 1 8 3

C h l o rot h al on i l Y

. 0 1 2 3

. 0 1 1 8 2 9 6 1 2

C l opy ral i d N

. 0 8 6 2

. 0 0 6 5 4 8 8 6

D act h a l m o n o aci d N .0851 .01148 13 85

D i cam b a N

. 0 9 1 8

. 0 1 5 2 7 1 7 9 2

D i c h l o r p r o p N nd nd nd nd

D i n o s e b N

. 0 8 2 3

. 0 0 6 8 3 8 8 2

MC PA N

. 0 7 8 6

. 0 0 9 3 1 1 2 7 9

MC P B Y

. 0 6 9 0

. 0 0 9 9 4 1 4 6 9

Pi cl oram N

. 0 9 0 4

. 0 1 1 3 3 1 3 9 0

T r i c l opy r N

. 0 9 0 7

. 0 1 6 0 4 1 8 9 1

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 44ANALYTICAL METHOD 45 Table 17. Accuracy and precision data from nine determinations of the method compounds fortified at 0.50 microgram per liter in organic-free water, under positive ionization conditions

[conc., concentration; Y/N, yes/no;  g/L, microgram per liter]

Compound Reported

as an estimated

conc. (Y/N) Mean

observed

conc. ( μ g/L) Standard

deviation

( μ g/L) Relative

standard

deviation (percent) Mean

accuracy (percent of true conc.)

2,4-D methyl ester N 0.6060 0.04205 7 121 2-Hydroxyatrazine Y .5415 .09270 17 108 3(4-chlorophenyl)-1-methyl urea N .5098 .02956 6 102 3-Hydroxycarbofuran N .4725 .04037 9 95

3-Ketocarbofuran Y .2774 .1582 57 55

Aldicarb Y .3883 .05049 13 78

Aldicarb sulfone Y .3783 .04853 13 76

Aldicarb sulfoxide Y .3747 .04017 11 75

Atrazine N .5250 .01725 3 105

Bendiocarb N .4330 .02770 6 87 Benomyl N .4329 .04982 12 87 Bensulfuron-methyl N .4756 .02557 5 95

Bromacil Y .4304 .05635 13 86

Caffeine N .4857 .04800 10 97 Carbaryl N .4523 .05996 13 90

Carbofuran N .4954 .02407 5 99 Chloramben methyl ester Y .4370 .05847 13 87 Chlorimuron-ethyl N .4794 .04320 9 96 Cycloate Y .3198 .05180 16 64 Deethylatrazine Y .4836 .02359 5 97 Deethyldeiopropylatrazine Y .4199 .03419 8 84 Deisopropylatrazine Y .4416 .05683 13 88 Diphenamid N .4554 .02355 5 91

Diuron N .4639 .00897 2 93

Fenuron N .4364 .05450 12 87

Flumetsulam Y .4383 .02062 5 88

Fluometuron N .4581 .01034 2 92 Imazaquin Y .5825 .02403 4 117 Imazethapyr Y .5589 .02199 4 112 Imidicloprid N .3844 .05725 15 77

Linuron N .4911 .01474 3 98 Metalaxyl N .4808 .01269 3 96

Methiocarb Y .4505 .03728 8 90 Methomyl Y .3890 .03807 10 78 Methomyl oxime Y .0757 .02830 37 15 Metsulfuron-methyl Y .6061 .08198 14 121

Neburon N .4703 .01215 3 94

Nicosulfuron N .4886 .01786 4 98

Norflurazon Y .4721 .02388 5 94 Oryzalin N .4175 .01890 5 84 Oxamyl N .3890 .03985 10 78 Oxamyl oxime Y .1049 .05437 52 21 Propham N .4630 .01057 2 93 Propiconazole N .4655 .03045 7 93 Propoxur N .4466 .02265 5 89

Siduron N .4446 .02779 6 89 Sulfometuron-methyl N .3896 .01961 5 78

Tebuthiuron N .5213 .01444 3 104

Terbacil Y .4191 .05142 12 84 Tribenuron-methyl Y .4235 .07477 18 85T a b l e 18. Ac c u r a c y and pr ec is ion data f r om nine deter m i nations of the m e thod c o m pounds f o r t if ied at

0.50 m i c r ogr am per liter in or ganic

- f r ee w a ter

, under negative ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D N 0

. 4 4 3 1 0

. 0 5 1 3 4 8 9 2,4- D B Y

. 3 0 7 8

. 0 2 7 2 0 6 2

A c i f l u orf e n N

. 3 9 1 8

. 0 3 3 9 2 7 8

Ben t azon Y

. 2 8 9 1

. 0 4 7 6 2 5 8

Brom ox y n i l Y

. 3 7 3 4

. 0 3 3 2 8 7 5

C h l o rot h al on i l Y

. 0 3 8 4

. 0 2 4 9 4 8

C l opy ral i d N

. 3 1 4 7

. 0 4 9 2 5 6 3

D act h a l m o n o aci d N .1600 .06604 32

D i cam b a N

. 3 8 9 4

. 0 2 9 4 4 7 8

D i ch l o r p r o p N

. 4 2 3 9

. 0 2 7 8 2 8 5

D i n o s e b N

. 3 9 2 2

. 0 4 5 6 4 7 8

M C PA N

. 4 6 6 2

. 0 3 2 6 3 9 3

M C P B Y

. 5 9 7 1

. 0 5 2 4 7 Relativ e st an d a rd

de v i a t ion ( p ercen t )

1 2

9

9

1 6

9

6 5

1 6

41

8

7

1 2

7

9 1 1 9

Pi cl oram N

. 3 8 2 8

. 0 7 6 2 5 2 0 7 7

N

. 4 2 5 6

. 0 3 1 3 2 7 8 5

T a b l e 19. Ac c u r a c y and pr ec is ion data f r om 10 deter m i nations of the m e thod c o m pounds f o r t if ied at

0.025 m i c r ogr am per liter in gr ound- w a ter s a m p les

, under pos itive ioniz a tion c onditions

[con c., con cen tration ; Y/N, y e s / n o ;  g / L

, m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) S t a nda r d

de v i a t ion

( μ g/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit ( μ g/L)

2,4- D m e t h y l es t e r 0.0228 0.00153 7 91 0.0049

Y T r i c l opy r

M ean obs e r v e d

c onc

. ( μ g/L)

N

2- H y drox y a t r azi n e

. 0 2 3 0

. 0 0 1 4 2 6 9 2

. 0 0 4 5 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .0226 .00106 5 90 .0034

3- H y drox y carbof u

r an N

. 0 2 9 4

. 0 0 2 3 3 8 1 1 8

. 0 0 7 4

3- K e t o carbof u

r an Y

. 0 0 9 9

. 0 0 0 3 5 4 4 0

. 0 0 1 1

A l di c a r b Y

. 0 2 1 8

. 0 0 1 1 2 5 8 7

. 0 0 3 6

A l di carb s u l f on e Y .0229 .00088 4 92 .0028

A l di carb s u l f ox i d e Y .0232 .00072 3 93 .0023

A t razi n e N

. 0 2 4 5

. 0 0 0 8 8 4 9 8

. 0 0 2 8

Ben d i o c a r b N

. 0 2 3 8

. 0 0 1 1 1 5 9 5

. 0 0 3 5

Ben o m y l N

. 0 2 3 1

. 0 0 1 4 9 6 9 3

. 0 0 4 7

Ben s u l f u

ron

- m e t h y l N

. 0 3 8 6

. 0 0 3 4 0 9 1 5 4

. 0 1 0 8

Brom aci l Y

. 0 2 2 5

. 0 0 1 0 5 5 9 0

. 0 0 3 3

C a f f e i n e N

. 0 2 3 8

. 0 0 0 6 1 3 9 5

. 0 0 1 9

C a rbary l N

. 0 2 3 7

. 0 0 0 6 2 3 9 5

. 0 0 2 0

C a rbof u

r an N

. 0 2 3 8

. 0 0 0 8 0 3 9 5

. 0 0 2 5

C h l o ram b en m e t h y l es t e r Y .0210 .00101 5 84 .0032

C h l o ri m u

ron

- et h y l N

. 0 2 3 9

. 0 0 1 5 0 6 9 5

. 0 0 4 8

C y cl oat e Y

. 0 2 4 0

. 0 0 3 0 7 1 3 9 6

. 0 0 9 7

D eet h y l a t r azi n e Y

. 0 2 2 9

. 0 0 0 9 2 4 9 2

. 0 0 2 9

D eet h y l d ei opropy l a t r azi n e Y

. 0 2 4 3

. 0 0 0 6 1 3 9 7

. 0 0 1 9

D e i s opropy l a t r azi n e Y

. 0 2 2 9

. 0 0 0 9 1 4 9 2

. 0 0 2 9

D i ph en am i d N

. 0 2 5 5

. 0 0 1 3 2 5 1 0 2

. 0 0 4 2

D i u r on N

. 0 2 4 4

. 0 0 0 5 6 2 9 8

. 0 0 1 8

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 46T a b l e 19. Ac c u r a c y and pr ec is ion data f r om 10 deter m i nations of the m e thod c o m pounds f o r t if ied at

0.025 m i c r ogr am per liter in gr ound- w a ter s a m p les

, under pos itive ioniz a tion c onditions —Continued

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. ( μ g/L) S t a nda r d

de v i a t ion

( μ g/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit ( μ g/L)

F e n u

r on N 0

. 0 2 2 3 0

. 0 0 1 0 1 5 8 9 0

. 0 0 3 2

F l u m et s u l a m Y

. 0 3 8 3

. 0 0 3 0 4 8 1 5 3

. 0 0 9 6

F l u o m e t u

ron N

. 0 2 4 4

. 0 0 0 6 5 3 9 7

. 0 0 2 1

Im azaqu i n Y

. 0 5 2 7

. 0 0 9 6 5 1 8 2 1 1

. 0 3 0 6

Im azeth a py

r Y

. 0 3 5 0

. 0 0 1 9 1 5 1 4 0

. 0 0 6 0

Im i d i c l opri d N

. 0 3 8 2

. 0 0 3 2 0 8 1 5 3

. 0 1 0 1

L i n u

r on N

. 0 2 4 0

. 0 0 1 0 6 4 9 6

. 0 0 3 4

M e t a l a x y l N

. 0 2 3 9

. 0 0 0 9 3 4 9 5

. 0 0 2 9

M e t h i o c a r b Y

. 0 2 3 9

. 0 0 0 9 7 4 9 6

. 0 0 3 1

M e t h om y l Y

. 0 2 3 5

. 0 0 1 1 3 5 9 4

. 0 0 3 6

M e t h om y l ox i m e Y .0091 .00097 11 37 .0031

M e t s u l f u

ron

- m e t h y l Y

. 0 3 9 6

. 0 0 5 4 3 1 4 1 5 9

. 0 1 7 2

N e bu ron N

. 0 2 3 7

. 0 0 1 0 0 4 9 5

. 0 0 3 2

N i cos u l f u

r on N

. 0 4 2 9

. 0 0 3 2 7 8 1 7 1

. 0 1 0 4

N o rf l u

razon Y

. 0 2 4 2

. 0 0 0 6 5 3 9 7

. 0 0 2 1

O r y zal i n N

. 0 2 2 5

. 0 0 1 7 2 8 9 0

. 0 0 5 4

O x am y l N

. 0 2 3 8

. 0 0 1 3 9 6 9 5

. 0 0 4 4

O x am y l ox i m e Y .0071 .00498 70 29 .0158 Proph am N

. 0 2 3 8

. 0 0 0 6 5 3 9 5

. 0 0 2 1 Propi con azol e N

. 0 2 2 1

. 0 0 1 5 8 7 8 8

. 0 0 5 0 Propox u r N

. 0 2 3 7

. 0 0 0 7 2 3 9 5

. 0 0 2 3

S i du ron N

. 0 2 3 6

. 0 0 0 9 0 4 9 4

. 0 0 2 9

S u l f om et u

r on

- m et h y l N

. 0 3 8 8

. 0 0 2 9 2 8 1 5 5

. 0 0 9 2

T e bu t h i u ron N

. 0 2 6 8

. 0 0 2 7 2 1 0 1 0 7

. 0 0 8 6

T e rbaci l Y

. 0 2 2 9

. 0 0 0 6 2 3 9 2

. 0 0 2 0

T r i b en u

r on

- m et h y l Y

. 0 1 5 7

. 0 0 2 0 3 1 3 6 3

. 0 0 6 4

Ta b l e 20 . Ac c u r a c y and pr ec is ion data f r om nine deter m i nations of the m e thod c o m pounds f o r t if ied at

0.025 m i c r ogr am per liter in gr ound- w a ter s a m p les

, under negative ioniz a tion c onditions

[con c., con cen tration ; Y/N, y e s / n o ;  g / L

, m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. ( μ g/L) S t a nda r d

de v i a t ion

( μ g/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit ( μ g/L)

2,4- D N 0

. 0 2 3 9 0

. 0 0 1 7 5 7 9 6 0

. 0 0 5 7 2,4- D B Y

. 0 2 2 7

. 0 0 1 6 9 7 9 1

. 0 0 5 5

A c i f l u orf e n N

. 0 2 3 6

. 0 0 1 3 2 6 9 4

. 0 0 4 3

Ben t azon Y

. 0 2 0 7

. 0 0 0 9 9 5 8 3

. 0 0 3 2

Brom ox y n i l Y

. 0 1 6 3

. 0 0 1 8 5 1 1 6 5

. 0 0 6 0

C h l o rot h al on i l Y

. 0 1 4 8

. 0 0 2 7 2 1 8 5 9

. 0 0 8 8

C l opy ral i d N

. 0 2 3 3

. 0 0 1 0 4 4 9 3

. 0 0 3 4

D act h a l m o n o aci d N

. 0 2 3 8

. 0 0 0 9 0 4 9 5

. 0 0 2 9

D i cam b a N

. 0 2 3 2

. 0 0 0 8 2 4 9 3

. 0 0 2 7

D i ch l o r p r o p N

. 0 2 3 8

. 0 0 1 5 9 7 9 5

. 0 0 5 2

D i n o s e b N

. 0 0 6 2

. 0 0 0 8 5 1 4 2 5

. 0 0 2 8

M C PA N

. 0 2 3 6

. 0 0 0 9 8 4 9 4

. 0 0 3 2

M C P B Y

. 0 2 0 5

. 0 0 0 9 9 5 8 2

. 0 0 3 2

Pi cl oram N

. 0 2 3 4

. 0 0 1 0 2 4 9 4

. 0 0 3 3

T r i c l opy r N

. 0 2 4 2

. 0 0 1 1 5 5 9 7

. 0 0 3 8

AN AL Y T I C AL M E T H O D 4 7T a b l e 21. Ac c u r a c y and pr ec is ion data f r om s i x deter m i nations of the m e thod c o m pounds f o r t if ied at 0.10

m i c r ogr am per liter in gr ound- w a ter s a m p les

, under pos itive ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D m e t h y l es t e r N 0.0826 0.01318 16 83

2- H y drox y a t r azi n e Y

. 1 2 2 6

. 0 2 9 6 5 2 4 1 2 3 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .0918 .01323 14 92

3- H y drox y carbof u

r an N

. 0 8 2 2

. 0 0 7 2 9 9 8 2

3- K e t o carbof u

r an Y

. 0 5 5 4

. 0 1 1 1 0 2 0 5 5

A l di c a r b Y

. 0 5 8 5

. 0 1 4 4 2 2 5 5 9

A l di carb s u l f on e Y .0473 .02192 46 47

A l di carb s u l f ox i d e Y .0735 .00649 9 73

A t razi n e N

. 0 8 2 7

. 0 1 3 2 2 1 6 8 3

Ben d i o c a r b N

. 0 6 5 3

. 0 0 2 8 2 4 6 5

Ben o m y l N

. 0 7 4 8

. 0 0 4 7 0 6 7 5

Ben s u l f u

ron

- m e t h y l N

. 1 2 6 0

. 0 0 9 4 5 8 1 2 6

Brom aci l Y

. 0 7 6 8

. 0 1 4 8 6 1 9 7 7

C a f f e i n e N

. 0 9 9 1

. 0 0 8 4 0 8 9 9

C a rbary l N

. 0 8 4 5

. 0 1 0 6 3 1 3 8 4

C a rbof u

r an N

. 0 8 4 4

. 0 0 9 4 4 1 1 8 4

C h l o ram b en m e t h y l es t e r Y .0811 .00521 6 81

C h l o ri m u

ron

- et h y l N

. 0 9 8 2

. 0 1 7 1 6 1 7 9 8

C y cl oat e Y

. 0 7 2 4

. 0 0 8 2 4 1 1 7 2

D eet h y l a t r azi n e Y

. 0 7 0 2

. 0 1 4 1 9 2 0 7 0

D eet h y l d ei opropy l a t r azi n e Y

. 0 8 2 5

. 0 0 6 3 9 8 8 2

D e i s opropy l a t r azi n e Y

. 0 6 5 1

. 0 1 3 0 4 2 0 6 5

D i ph en am i d N

. 0 8 4 2

. 0 1 0 0 9 1 2 8 4

D i u r on N

. 0 9 0 0

. 0 1 3 3 5 1 5 9 0

F e n u

r on N

. 0 7 9 6

. 0 1 0 8 1 1 4 8 0

F l u m et s u l a m Y

. 1 7 2 5

. 0 0 7 6 1 4 1 7 2

F l u o m e t u

ron N

. 0 8 6 3

. 0 1 0 2 7 1 2 8 6

Im azaqu i n Y

. 1 4 5 5

. 0 1 9 0 4 1 3 1 4 5

Im azeth a py

r Y

. 1 8 0 7

. 0 5 8 3 1 3 2 1 8 1

Im i d i c l opri d N

. 1 4 5 3

. 0 1 4 5 5 1 0 1 4 5

L i n u

r on N

. 0 8 8 7

. 0 1 0 1 4 1 1 8 9

M e t a l a x y l N

. 0 8 7 2

. 0 0 9 8 0 1 1 8 7

M e t h i o c a r b Y

. 0 8 9 1

. 0 1 1 4 3 1 3 8 9

M e t h om y l Y

. 0 7 8 5

. 0 1 6 7 6 2 1 7 8

M e t h om y l ox i m e Y .0111 .00100 9 11

M e t s u l f u

ron

- m e t h y l Y

. 1 4 3 6

. 0 3 0 4 9 2 1 1 4 4

N e bu ron N

. 0 8 6 0

. 0 1 5 4 2 1 8 8 6

N i cos u l f u

r on N

. 1 7 4 0

. 0 1 2 2 2 7 1 7 4

N o rf l u

razon Y

. 0 9 3 0

. 0 1 0 9 4 1 2 9 3

O r y zal i n N

. 0 9 0 5

. 0 1 2 5 1 1 4 9 0

O x am y l N

. 0 7 0 0

. 0 0 7 2 4 1 0 7 0

O x am y l ox i m e Y .0238 .01125 47 24 Proph am N

. 0 8 0 3

. 0 1 1 6 4 1 4 8 0 Propi con azol e N

. 0 9 7 2

. 0 0 8 0 8 8 9 7 Propox u r N

. 0 8 0 7

. 0 0 9 2 6 1 1 8 1

S i du ron N

. 0 9 9 6

. 0 1 4 8 1 1 5 1 0 0

S u l f om et u

r on

- m et h y l N

. 1 5 4 6

. 0 1 2 0 0 8 1 5 5

T e bu t h i u ron N

. 0 9 6 1

. 0 1 5 5 5 1 6 9 6

T e rbaci l Y

. 0 7 9 5

. 0 1 4 3 3 1 8 8 0

T r i b en u

r on

- m et h y l Y

. 0 4 3 4

. 0 2 2 7 1 5 2 4 3

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 48Ta b l e 22 . Ac c u r a c y and pr ec is ion data f r om s i x deter m i nations of the m e thod c o m pounds f o r t if ied at 0.10

m i c r ogr am per liter in gr ound- w a ter s a m p les

, under negative ioniz a tion c onditions

[con c., con cen tration ; Y/N; y e s / n o ;  g / L

, m i cro g ram p e r liter; n d , n o t d e term in ed ]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. ( μ g/L) S t a nda r d

de v i a t ion

( μ g/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D Y 0

. 0 6 4 6 0

. 0 0 4 6 8 7 6 5 2,4- D B N

. 0 7 4 8

. 0 0 6 5 4 9 7 5

A c i f l u orf e n N

. 0 7 8 0

. 0 1 1 8 0 1 5 7 8

Ben t azon N

. 0 6 0 0

. 0 0 2 8 2 5 6 0

Brom ox y n i l Y

. 0 7 3 8

. 0 0 5 3 1 7 7 4

C h l o rot h al on i l Y

. 0 4 8 6

. 0 1 3 5 9 2 8 4 9

C l opy ral i d N

. 0 7 5 5

. 0 0 9 7 5 1 3 7 5

D act h a l m o n o aci d N .0777 .00770 10 78

D i cam b a Y

. 0 7 8 6

. 0 0 9 5 9 1 2 7 9

D i c h l o r p r o p Y nd nd nd nd

D i n o s e b N

. 0 7 9 2

. 0 0 3 9 0 5 7 9

M C PA Y

. 0 7 2 5

. 0 0 5 5 6 8 7 3

M C P B N

. 0 6 5 1

. 0 0 6 1 4 9 6 5

Pi cl oram N

. 0 8 2 1

. 0 0 6 2 5 8 8 2

T r i c l opy r Y

. 0 8 3 5

. 0 1 3 1 7 1 6 8 3

T a b l e 23. Ac c u r a c y and pr ec is ion data f r om 11 deter m i nations of the m e thod c o m pounds f o r t if ied at 0.50

m i c r ogr am per liter in gr ound- w a ter s a m p les

, under pos itive ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D m e t h y l es t e r N 0.6056 0.03970 7 121

2- H y drox y a t r azi n e Y

. 5 5 0 3

. 0 9 0 6 7 1 6 1 1 0 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .5286 .07316 14 106

3- H y drox y carbof u

r an N

. 4 7 4 0

. 0 3 8 0 3 8 9 5

3- K e t o carbof u

r an Y

. 2 9 9 4

. 0 3 0 8 8 1 0 6 0

A l di c a r b Y

. 2 4 4 0

. 1 5 4 0 6 6 3 4 9

A l di carb s u l f on e Y .2038 .16250 80 41

A l di carb s u l f ox i d e Y .2546 .11533 45 51

A t razi n e N

. 5 0 3 1

. 0 7 2 8 1 1 4 1 0 1

Ben d i o c a r b N

. 6 6 6 3

. 1 6 4 1 1 2 5 1 3 3

Ben o m y l N

. 4 0 4 2

. 1 0 8 7 9 2 7 8 1

Ben s u l f u

ron

- m e t h y l N

. 4 3 4 0

. 1 3 8 6 5 3 2 8 7

Brom aci l Y

. 3 8 8 4

. 0 9 0 4 1 2 3 7 8

C a f f e i n e N

. 3 4 0 4

. 2 1 6 8 4 6 4 6 8

C a rbary l N

. 4 4 4 8

. 1 0 7 8 1 2 4 8 9

C a rbof u

r an N

. 4 7 0 3

. 0 9 7 6 3 2 1 9 4

C h l o ram b en m e t h y l es t e r Y .3528 .14311 41 71

C h l o ri m u

ron

- et h y l N

. 4 7 8 4

. 0 3 9 2 5 8 9 6

AN AL Y T I C AL M E T H O D 4 9T a b l e 23. Ac c u r a c y and pr ec is ion data f r om 11 deter m i nations of the m e thod c o m pounds f o r t if ied at

0.50 m i c r ogr am per liter in gr ound- w a ter s a m p les

, under pos itive ioniz a tion c onditions —Continued

Compound Re por te d a s

an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

C y cl oat e Y 0

. 2 1 0 2 0

. 1 3 3 6 1 6 4 4 2

D eet h y l a t r azi n e Y

. 4 8 3 8

. 0 2 2 0 7 5 9 7

D eet h y l d ei opropy l a t r azi n e Y

. 4 1 7 6

. 1 8 5 8 3 4 4 8 4

D e i s opropy l a t r azi n e Y

. 3 3 8 7

. 1 9 1 3 4 5 6 6 8

D i ph en am i d N

. 4 1 3 0

. 1 3 8 1 4 3 3 8 3

D i u r on N

. 4 5 1 5

. 0 4 7 7 2 1 1 9 0

F e n u

r on N

. 4 3 6 7

. 0 5 0 9 9 1 2 8 7

F l u m et s u l a m Y

. 4 4 0 7

. 0 2 0 6 0 5 8 8

F l u o m e t u

ron N

. 4 5 6 3

. 0 1 5 5 2 3 9 1

Im azaqu i n Y

. 5 5 7 0

. 0 9 9 9 5 1 8 1 1 1

Im azeth a py

r Y

. 5 1 8 8

. 0 8 6 8 4 1 7 1 0 4

Im i d i c l opri d N

. 3 7 7 1

. 0 6 6 5 4 1 8 7 5

L i n u

r on N

. 4 9 2 2

. 0 1 4 8 6 3 9 8

M e t a l a x y l N

. 4 3 7 6

. 1 4 2 6 7 3 3 8 8

M e t h i o c a r b Y

. 2 8 0 5

. 1 9 1 7 5 6 8 5 6

M e t h om y l Y

. 2 7 5 6

. 1 4 2 0 5 5 2 5 5

M e t h om y l ox i m e Y .0641 .03562 56 13

M e t s u l f u

ron

- m e t h y l Y

. 6 6 8 5

. 1 6 3 4 5 2 4 1 3 4

N e bu ron N

. 4 7 1 6

. 0 1 1 5 7 2 9 4

N i cos u l f u

r on N

. 4 6 2 7

. 0 8 0 0 9 1 7 9 3

N o rf l u

razon Y

. 3 8 7 7

. 1 2 8 9 7 3 3 7 8

O r y zal i n N

. 3 8 3 6

. 1 1 2 9 5 2 9 7 7

O x am y l N

. 3 1 9 9

. 0 9 5 0 0 3 0 6 4

O x am y l ox i m e Y .0887 .04992 56 18 Proph am N

. 4 3 1 2

. 1 2 6 0 1 2 9 8 6 Propi con azol e N

. 4 2 4 1

. 1 3 6 2 8 3 2 8 5 Propox u r N

. 4 2 5 1

. 0 7 4 8 3 1 8 8 5

S i du ron N

. 4 0 6 4

. 1 0 9 4 8 2 7 8 1

S u l f om et u

r on

- m et h y l N

. 3 5 8 7

. 1 0 3 1 9 2 9 7 2

T e bu t h i u ron N

. 5 2 2 5

. 0 1 3 6 3 3 1 0 5

T e rbaci l Y

. 4 1 1 5

. 0 5 0 4 6 1 2 8 2

T r i b en u

r on

- m et h y l Y

. 3 1 9 6

. 1 1 7 1 6 3 7 6 4



### from the data for mean recoveries of individual compounds. No method compounds were detected in the g r oundwater samples, so no backg r ound correction was required.

11.3.2 The mean positive

ioniz a tion recoveries for compounds from the g r ound-water sample s reported without qualification (tables 19, 21, and 23) were

104.8  23.1, 95.0  25.1, and 90.2  14.6 percent at fortifications of 0.025, 0.100, and

0.500  g / L

, respect i v el y

. The m e di an r e c ove r i e s we r e simila r to the me a n s, a t 95.0, 86.5, and 88.5 percent, respectively

. Mean recoveries of compounds reported as

qua lif ie d e s tima te s we r e mor e va r i a b le , a t

96.6  40.8, 84.7  43.9, and 70.6  30.1 percent, with corresponding medians of 92.0, 77.5, and 69.5 percent, respectively

.

11.3.3 Mean recoveries determined by neg a tive ioniz a tion and reported without qualifi cation in the g r oundwater samples (tables 20, 22, and 24)

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 50Ta b l e 24 . Ac c u r a c y and pr ec is ion data f r om 10 deter m i nations of the m e thod c o m pounds f o r t if ied at 0.50

m i c r ogr am per liter in gr ound- w a ter s a m p les

, under negative ioniz a tion c onditions

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter; n d , n o t d e term in ed ]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc . (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)

2,4- D N 0

. 0 7 2 2 0

. 0 1 2 3 1 1 7 7 2 2,4- D B N

. 0 7 0 5

. 0 0 8 5 6 1 2 7 1

A c i f l u orf e n Y

. 0 8 4 7

. 0 0 9 9 0 1 2 8 5

Ben t azon N

. 0 6 1 2

. 0 0 3 0 7 5 6 1

Brom ox y n i l N

. 0 8 2 7

. 0 0 9 0 9 1 1 8 3

C h l o rot h al on i l N

. 0 1 2 3

. 0 1 1 8 2 9 6 1 2

C l opy ral i d N

. 0 8 6 2

. 0 0 6 5 4 8 8 6

D act h a l m o n o aci d N .0851 .01148 13 85

D i cam b a N

. 0 9 1 8

. 0 1 5 2 7 1 7 9 2

D i c h l o r p r o p Y nd nd nd nd

D i n o s e b Y

. 0 8 2 3

. 0 0 6 8 3 8 8 2

M C PA N

. 0 7 8 6

. 0 0 9 3 1 1 2 7 9

M C P B Y

. 0 6 9 0

. 0 0 9 9 4 1 4 6 9

Pi cl oram N

. 0 9 0 4

. 0 1 1 3 3 1 3 9 0

T r i c l opy r Y

. 0 9 0 7

. 0 1 6 0 4 1 8 9 1



### averag ed slig htly lower, at 87.6  22.0, 74.0

 7.6 and 73.1  23.5 percent, at fortifications
of 0.025, 0.100, and 0.500  g / L

, respect i v el y

. The me dia n r e c ove r i e s we r e simila r to the means, at 94.0, 76.5, and 81.0 percent,

r e spe c tive l y

. I n this ma tr ix , me a n r e c ove r i e s of compounds reported as qualified estimates

were similar to com pounds reported without
qualification, at 76.0  13.4, 70.5  12.2, and

81.8  9.3 percent, with corresponding medians of 92.0, 77.5, and 69.5 percent,

respect i v el y

.

11.3.4 I n the g r ound-water samples, averag e recoveries of all compounds reported without qualifi cation at all three

fortification leve ls varied about  20.9 percent for compounds determined by positive

ioniz a tion and  17.7 percent for compounds determined by neg a tive ioniz a tion. This

resul t

, however, does not refl ect t h e anal y t i cal precision, which is better reflected by the

relative standard devi ation of individual compound recoveries in the g r ound-water

sa mple s, pa r tic ula r ly those that are reported without quantitation qua lification. Under positive ioniz a tion conditions, the mean relative standard deviations for compounds reported without qualif ication in the g r oundwater samples were 5.4  2.2, 11.7  3.6, and

20.5  13.5 percent for 0.025-, 0.100-, and

0.500- μ g / L f o r tif ic a tions, r e spe c tive l y

. The corresponding relative sta ndard deviations for

neg a tive ioniz a tion results reported without qualification in the g r ound-water samples

were 5.9  3.1, 9.2  3.5, and 20.4  26.8 percent for 0.025-, 0.100-, and 0.500- μ g/ L

fort i f i cat i ons, respect i v el y

. The g r eat er

va r i a b ility in the r e la tive sta nda r d de via tion for compounds determined by neg a tive

ioniz a tion in the 0.500- μ g / L f o r tif ic a tion wa s the r e sult of pa r tic ula r ly variable recovery of

c h lor o tha l onil. I f this r e sult is e x c l ude d, the n the me a n r e la tive sta nda rd deviation was 12 ± 3.8 percent, similar to the mean relative

standard deviations reported for the other

f o r tif ic a tions.

11.4 S u rface-wat e r fort i f i cat i on

recovery resul t s

AN AL Y T I C AL M E T H O D 5 1

### 11.4.1 I n contrast to the other

m a t r i ces t e st ed, one set of 10 surface-wat e r samples was fortified at 0.050  g / L as t h e lowe st f o r tif ic a tion c onc e n tr a tion r a the r tha n

0.025  g / L

, as was t h e case wi t h t h e reag ent

water and g r ound-wate r fortification

ex peri m e nt s. Thi s chang e was m a de because of nonspecific matrix interferences. Concentrations of dissolved org a nic carbon,

t h e l i k el y source of t h ese i n t e rferences i n t h e South Platte River, ty pically rang ed between 3 and 30 mg /L (L itke and Kimbroug h, 1998), althoug h median concen trations were 5.2 and 7.0 mg /L in the South Platte River at Denver and Henderson, Colorado, respectively

. The

r e ma ining two se ts of sa mple s we r e f o r tif ie d

at 0.100 and 0.500  g / L

, ide n tic a l to the

org a nic-free and g r ound-wa ter fortifications.

The surface-wat e r fort i f i cat i on ex peri m e nt s at

0.100  g / L were conducted 8 months prior to

the 0.05 and 0.5 fortifications. All results are listed in tables 25 throug h 31. The mean, median, and the sta ndard deviation of

recovery for all compounds in the tables were

cal cul a t e d from t h e dat a for m ean recoveri es of individual compounds. I n comparison to the reag ent-water and g r ound-water samples, measurable concentrations of a few method analy t es were detected. Caffeine, 2-hy drox y

atraz i ne, atraz i ne, di uron, 2,4-D, and MCPA

were det ect ed i n at l east t w o of t h ree repl i cat e unspi ked S out h P l at t e surface-wat e r sam p l e s. The m ean concent r at i ons are l i s t e d i n t a bl e 25. Spiked South Platte River surface-water

resul t s were correct ed for am bi ent concentrations prior to calculation of

recoveries.

11.4.2 Compound recoveries from

t h e surface-wat e r sam p l e s were hi g h er, oft e n substantially g r eater than 100 percent at the

0.05- and 0.5-  g / L fortifications, and more variable between compounds than in either the org a nic-free water or the g r ound-water

sa mple s. The me a n positive ioniza tion

recovery results for compounds reported without qualification in the surface-water
samples were 131  66.3, 90.8  10.0, and

125  93.5 percent at fortifications of 0.050,
0.100, and 0.500  g / L

, respect i v el y

. The

me dia n r e c ove r i e s we r e simila r to the me a n s at 119.0, 87.0, and 108.0 percent, respectively

. F o r those compounds determined under positive ion conditions and

T a b l e 25. Am bient pes tic i de c onc entr a tions m eas ur ed in South Platte River s a m p les dur ing this s t udy [ μ g / L

, m i cro g ram p e r liter]

Compound M ean d e t ect ed

co n cen t r at io n s , in μg/L S t a nda r d de v i a t ion of

mean d e t ect ed

co n cen t r at io n s , in μg/L Number of

de te c t ions /numbe r of

de te r m ina t ions

2,4- D 0

. 1 9 2 5 0

. 1 0 2 5 2/ 2

2- H y drox y a t r azi n e

. 0 6 4 5

. 0 0 2 1 2/ 3

A t razi n e

. 0 0 6 5

. 0 0 0 7 3/ 3

C a f f e i n e

. 1 0 3 3

. 0 1 1 2 3/ 3

D i u r on

. 0 3 8 0

. 0 0 6 6 3/ 3

M C PA

. 0 2 5 0

. 0 1 5 6 2/ 2

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 52T a b l e 26. Ac c u r a c y and pr ec is ion data f r om nine deter m i nations of the m e thod c o m pounds f o r t if ied at

0.05 m i c r ogr am per liter in s u r f ac e- w a ter s a m p les

, under pos itive ioniz a tion c onditions . Rec o ver i es

c o r r e c t ed f o r am bient c o m pound c onc entr a tions lis ted in table 25

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit (μg/L)

2,4- D m e t h y l es t e r N 0.0173 0.00543 31 35 0.0177

2- H y drox y a t r azi n e Y

. 0 3 6 2

. 0 0 4 4 9 1 2 7 2

. 0 1 4 6 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .0442 .00380 9 88 .0124

3- H y drox y carbof u

r an N

. 0 5 0 1

. 0 0 5 2 5 1 0 1 0 0

. 0 1 7 1

3- K e t o carbof u

r an Y

. 0 0 3 2

. 0 0 0 4 5 1 4 6

. 0 0 1 5

A l di c a r b Y

. 0 4 3 9

. 0 0 6 6 8 1 5 8 8

. 0 2 1 7

A l di carb s u l f on e Y .0363 .00700 19 73 .0227

A l di carb s u l f ox i d e Y .0247 .00173 7 49 .0056

A t razi n e N

. 0 5 3 6

. 0 0 4 1 6 8 1 0 7

. 0 1 3 5

Ben d i o c a r b N

. 0 1 2 4

. 0 0 4 5 3 3 6 2 5

. 0 1 4 7

Ben o m y l N

. 0 4 5 9

. 0 0 4 1 7 9 9 2

. 0 1 3 5

Ben s u l f u

ron

- m e t h y l N

. 1 4 4 6

. 0 0 7 5 7 5 2 8 9

. 0 2 4 6

Brom aci l Y

. 0 2 8 9

. 0 0 3 1 4 1 1 5 8

. 0 1 0 2

C a f f e i n e N

. 0 5 4 1

. 0 1 0 6 5 2 0 1 0 8

. 0 3 4 6

C a rbary l N

. 0 4 1 2

. 0 0 4 7 4 1 1 8 2

. 0 1 5 4

C a rbof u

r an N

. 0 4 8 4

. 0 0 3 1 7 7 9 7

. 0 1 0 3

C h l o ram b en m e t h y l es t e r Y .0737 .00433 6 147 .0141

C h l o ri m u

ron

- et h y l N

. 1 1 4 3

. 0 0 9 5 3 8 2 2 9

. 0 3 2 0

C y cl oat e Y

. 0 2 3 6

. 0 0 6 0 9 2 6 4 7

. 0 1 9 8

D eet h y l a t r azi n e Y

. 0 4 6 6

. 0 0 3 0 5 7 9 3

. 0 0 9 9

D eet h y l d ei opropy l a t r azi n e Y

. 0 2 5 6

. 0 0 2 7 7 1 1 5 1

. 0 0 9 3

D e i s opropy l a t r azi n e Y

. 0 3 8 6

. 0 0 3 0 9 8 7 7

. 0 1 0 0

D i ph en am i d N

. 0 6 7 6

. 0 0 3 8 8 6 1 3 5

. 0 1 2 6

D i u r on N

. 0 6 0 6

. 0 0 6 0 4 1 0 1 2 1

. 0 1 9 6

F e n u

r on N

. 0 5 1 9

. 0 0 6 8 8 1 3 1 0 4

. 0 2 2 4

F l u m et s u l a m Y

. 1 0 0 3

. 0 0 8 7 3 9 2 0 1

. 0 2 8 4

F l u o m e t u

ron N

. 0 6 2 3

. 0 0 3 4 6 6 1 2 5

. 0 1 1 3

Im azaqu i n Y

. 1 0 6 9

. 0 0 6 4 3 6 2 1 4

. 0 2 0 9

Im azeth a py

r Y

. 2 2 1 0

. 0 1 3 7 7 6 4 4 2

. 0 4 4 7

Im i d i c l opri d N

. 0 7 2 9

. 0 1 1 7 9 1 6 1 4 6

. 0 3 8 3

L i n u

r on N

. 0 6 8 3

. 0 0 6 3 2 9 1 3 7

. 0 2 0 6

M e t a l a x y l N

. 0 6 6 3

. 0 0 3 7 4 6 1 3 3

. 0 1 2 2

M e t h i o c a r b Y

. 0 3 9 6

. 0 0 5 1 5 1 3 7 9

. 0 1 6 7

M e t h om y l Y

. 0 6 5 4

. 0 0 5 4 3 8 1 3 1

. 0 1 7 7

M e t h om y l ox i m e Y .0038 .00158 42 8 .0053

M e t s u l f u

ron

- m e t h y l Y

. 0 1 2 4

. 0 0 4 5 0 3 6 2 5

. 0 1 4 6

N e bu ron N

. 0 5 8 3

. 0 0 4 5 0 8 1 1 7

. 0 1 4 6

N i cos u l f u

r on N

. 1 5 6 3

. 0 1 1 6 8 7 3 1 3

. 0 3 8 0

N o rf l u

razon Y

. 0 6 7 1

. 0 0 3 6 9 5 1 3 4

. 0 1 2 0

O r y zal i n N

. 0 6 0 6

. 0 1 5 0 0 2 5 1 2 1

. 0 4 8 8

O x am y l N

. 0 4 8 7

. 0 1 1 5 0 2 4 9 7

. 0 3 7 4

O x am y l ox i m e Y .0241 .00326 14 48 .0106 Proph am N

. 0 4 5 7

. 0 0 5 6 6 1 2 9 1

. 0 1 8 4 Propi con azol e N

. 0 6 3 7

. 0 0 5 0 2 8 1 2 7

. 0 1 6 3 Propox u r N

. 0 5 1 6

. 0 0 2 4 0 5 1 0 3

. 0 0 7 8

S i du ron N

. 0 7 4 4

. 0 0 4 3 9 6 1 4 9

. 0 1 4 3

S u l f om et u

r on

- m et h y l N

. 1 2 9 1

. 0 0 6 4 5 5 2 5 8

. 0 2 1 0

T e bu t h i u ron N

. 0 6 3 8

. 0 0 4 3 2 7 1 2 8

. 0 1 4 1

T e rbaci l Y

. 0 2 3 6

. 0 0 3 3 4 1 4 4 7

. 0 1 1 2

T r i b en u

r on

- m et h y l Y

. 0 9 7 4

. 0 0 6 6 5 7 1 9 5

. 0 2 1 6

AN AL Y T I C AL M E T H O D 5 3Ta b l e 27. Ac c u r a c y and pr ec is ion data f r om nine deter m i nations of the m e thod c o m pounds f o r t if ied at

0.05 m i c r ogr am per liter in s u r f ac e- w a ter s a m p les

, under negative ioniz a tion c onditions . Rec o ver i es

c o r r e c t ed f o r am bient c o m pound c onc entr a tions lis ted in table 25

[con c., con cen tration ; Y/N, y e s / n o ;  g / L

, m i cro g ram p e r liter; n d , n o t d e term in ed ]

Compound Re por te d

as an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .) M e thod

de te c t ion

limit (μg/L)

2,4- D N 0

. 0 2 2 6 0

. 0 0 4 7 7 2 1 4 5 0

. 0 1 5 5 2,4- D B Y

. 0 2 5 2

. 0 0 2 9 5 1 2 5 0

. 0 0 9 6

A c i f l u orf e n N

. 0 2 6 1

. 0 0 1 1 2 4 5 2

. 0 0 3 6

Ben t azon Y

. 0 2 4 9

. 0 0 2 8 9 1 2 5 0

. 0 0 9 4

Brom ox y n i l Y

. 0 2 6 0

. 0 0 1 3 2 5 5 2

. 0 0 4 3

C h l o rot h al on i l Y

. 0 2 5 8

. 0 0 3 1 1 1 2 5 2

. 0 1 0 1

C l opy ral i d N

. 3 0 5 7

. 0 1 4 2 5 5 6 1 1

. 0 4 6 3

D act h a l m o n o aci d N .0159 .00401 25 32 .0130

D i cam b a N

. 0 2 5 1

. 0 0 2 8 0 1 1 5 0

. 0 0 9 1

D i ch l o r p r o p N

. 0 1 3 4

. 0 0 8 3 7 6 2 2 7

. 0 2 7 2

D i n o s e b N

. 0 5 9 1

. 0 0 3 3 7 6 1 1 8

. 0 1 1 0

M C P A N nd nd nd nd nd

M C P B Y

. 0 2 6 3

. 0 0 1 8 7 7 5 3

. 0 0 6 1

Pi cl oram N

. 0 2 6 1

. 0 0 3 0 2 1 2 5 2

. 0 0 9 8

T r i c l opy r N

. 0 2 3 4

. 0 0 1 1 3 5 4 7

. 0 0 3 7

T a b l e 28. Ac c u r a c y and pr ec is ion data f r om s i x deter m i nations of the m e thod c o m pounds f o r t if ied at 0.10

m i c r ogr am per liter in s u r f ac e- w a ter s a m p les

, under pos itive ioniz a tion c onditions . Rec o ver i es c o r r e c t ed

f o r am bient c o m pound c onc entr a tions lis ted in table 25

[co n c., co n cen tratio n ; Y/N, y e s/n o ; μ g /L , m i cro g ram p e r liter; n d , n o t d e term in ed ; n a , n o t av ailab l e]

Compound Re por te d a s

an est imat ed

c onc

. (Y/N) M ean obs e r v e d

c onc

. (μg/L) S t a nda r d

de v i a t ion

(μg/L) Relativ e st an d a rd

de v i a t ion ( p ercen t ) M ean

accu racy ( p ercen t o f

tr ue c onc .)
2,4- D m e t h y l es t e r N 0.0780 0.01388 18 78

2- H y drox y a t r azi n e Y

. 1 0 8 6

. 0 3 1 0 0 2 9 1 0 9 3(4- ch l o roph en y l )- 1- m e t h y l u r ea N .0997 .01584 16 100

3- H y drox y carbof u

r an N

. 0 9 1 6

. 0 1 0 5 9 1 2 9 2

3- K e t o carbof u

r an Y

. 0 8 2 2

. 0 1 2 6 0 1 5 8 2

A l di c a r b Y

. 0 6 2 2

. 0 1 4 1 7 2 3 6 2

A l di carb s u l f on e Y .0649 .02707 42 65

A l di carb s u l f ox i d e Y .0758 .00418 6 76

A t razi n e N

. 0 9 2 5

. 0 1 2 0 2 1 3 9 2

Ben d i o c a r b N

. 0 8 5 2

. 0 1 0 3 9 1 2 8 5

Ben o m y l N

. 0 8 0 9

. 0 0 2 1 2 3 8 1

Ben s u l f u

ron

- m e t h y l N

. 0 9 2 1

. 0 0 6 5 7 7 9 2

Brom aci l Y

. 0 9 2 8

. 0 1 3 2 2 1 4 9 3

C a f f e i n e N

. 1 0 8 5

. 0 1 3 8 0 1 3 1 0 9

C a rbary l N

. 0 8 7 7

. 0 1 0 7 0 1 2 8 8

C a rbof u

r an N

. 0 8 4 6

. 0 0 9 8 1 1 2 8 5

C h l o ram b en m e t h y l es t e r Y .0928 .01962 21 93

C h l o ri m u

ron

- et h y l N

. 0 8 4 8

. 0 0 4 4 8 5 8 5

C y cl oat e Y

. 0 7 0 5

. 0 0 8 3 8 1 2 7 1

D eet h y l a t r azi n e Y

. 1 0 8 0

. 0 1 4 9 0 1 4 1 0 8

D eet h y l d ei opropy l a t r azi n e Y

. 0 8 7 7

. 0 1 0 3 4 1 2 8 8

D e i s opropy l a t r azi n e Y

. 1 0 5 5

. 0 1 2 6 5 1 2 1 0 5

D i ph en am i d N

. 0 8 3 4

. 0 0 9 3 9 1 1 8 3

D i u r on N

. 0 8 9 9

. 0 1 2 6 7 1 4 9 0

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 54ANALYTICAL METHOD 55 Table 28. Accuracy and precision data from six determinations of the method compounds fortified at 0.10 microgram per liter in surface-water samples, under positive ionization conditions. Recoveries corrected for ambient compound concentrations listed in table 25—Continued

Compound Reported as

an estimated

conc. (Y/N) Mean

observed

conc. (μg/L) Standard

deviation

(μg/L) Relative

standard

deviation (percent) Mean

accuracy (percent of true conc.)

Fenuron N 0.0856 0.01263 15 86

Flumetsulam Y .1302 .01003 8 130

Fluometuron N .0865 .01046 12 86 Imazaquin Y .1620 .01256 8 162 Imazethapyr Y nd nd nd nd Imidicloprid N .0956 .01620 17 96

Linuron N .0864 .01184 14 86 Metalaxyl N .0835 .00985 12 83

Methiocarb Y .0870 .01324 15 87 Methomyl Y .0796 .01282 16 80 Methomyl oxime Y .0129 .00008 1 13 Metsulfuron-methyl Y .0746 .01945 26 75

Neburon N .0886 .01225 14 89

Nicosulfuron N .1261 .00532 4 126

Norflurazon Y .0918 .01335 15 92 Oryzalin N .0860 .01175 na 86 Oxamyl N .0841 .00244 3 84 Oxamyl oxime Y .0256 .01120 44 26 Propham N .0824 .01114 14 82 Propiconazole N .0978 .00927 9 98 Propoxur N .0846 .01011 12 85

Siduron N .0939 .01512 16 94 Sulfometuron-methyl N .0962 .00355 4 96

Tebuthiuron N .1052 .01302 12 105

Terbacil Y .0952 .01614 17 95 Tribenuron-methyl Y .0278 .01141 41 28

Table 29 . Accuracy and precision data from six determinations of the method compounds fortified at 0.10 microgram per liter in surface-water samples, under negative ionization conditions. Recoveries corrected for ambient compound concentrations listed in table 25

[conc., concentration; Y/N, yes/no; μg/L, microgram per liter; nd, not determined]

Compound Reported as

an estimated

conc. (Y/N) Mean

observed

conc. (μg/L) Standard

deviation

(μg/L) Relative

standard

deviation (percent) Mean

accuracy (percent of true conc.)
2,4-D N 0.0692 0.00858 12 69 2,4-DB N .0672 .00855 13 67

Acifluorfen Y .0732 .00775 11 73

Bentazon N .0573 .00425 7 57 Bromoxynil N .0649 .00613 9 65

Chlorothalonil N .0764 .01028 13 76 Clopyralid N .0501 .01623 32 50

Dacthal monoacid N .0744 .00804 11 74

Dicamba N .0733 .00890 12 73 Dichlorprop Y nd nd nd nd

Dinoseb Y .0743 .00440 6 74

MCPA N .0751 .00535 7 75

MCPB Y .0651 .00921 14 65

Picloram N .0871 .00765 9 87 Triclopyr Y .0789 .00898 11 79Pesticides in Water by Graphitized Carbon-Based SPE and HPLC/MS 56 Table 30. Accuracy and precision data from eight determinations of the method compounds fortified at 0.50 microgram per liter in surface-water samples, under positive ionization conditions. Recoveries corrected for ambient compound concentrations listed in table 25

[conc., concentration; Y/N, yes/no; μg/L, microgram per liter]

Compound Reported as

an estimated

conc. (Y/N) Mean

observed

conc. (μg/L) Standard

deviation

(μg/L) Relative

standard

deviation (percent) Mean

accuracy (percent of true conc.) 2,4-D methyl ester N 0.0123 0.01210 98 2 2-Hydroxyatrazine Y .4449 .16531 37 89 3(4-chlorophenyl)-1-methyl urea N .4648 .04682 10 93 3-Hydroxycarbofuran N .1589 .10825 68 32

3-Ketocarbofuran Y .0058 .00096 17 1

Aldicarb Y .3174 .07261 23 63

Aldicarb sulfone Y .2719 .07615 28 54

Aldicarb sulfoxide Y .5699 .15729 28 114

Atrazine N .5258 .07168 14 105

Bendiocarb N .0069 .00544 79 1 Benomyl N .4231 .04948 12 85 Bensulfuron-methyl N 1.9925 .30680 15 399

Bromacil Y .2469 .01911 8 49

Caffeine N .6533 .06538 10 131 Carbaryl N .0839 .07925 94 17

Carbofuran N .2638 .14014 53 53 Chloramben methyl ester Y .8634 .07006 8 173 Chlorimuron-ethyl N 1.4456 .10097 7 289 Cycloate Y .1804 .08792 49 36 Deethylatrazine Y .4493 .06076 14 90 Deethyldeiopropylatrazine Y .0443 .01743 39 9 Deisopropylatrazine Y .3958 .05684 14 79 Diphenamid N .6759 .07794 12 135

Diuron N .6533 .06118 9 131

Fenuron N .5284 .04383 8 106

Flumetsulam Y 1.0458 .09840 9 209

Fluometuron N .6446 .06166 10 129 Imazaquin Y 1.3143 .14009 11 263 Imazethapyr Y 1.5173 .04774 3 303 Imidicloprid N .8706 .08315 10 174

Linuron N .5155 .07320 14 103 Metalaxyl N .7384 .08215 11 148

Methiocarb Y .1597 .02914 18 32 Methomyl Y .6341 .12760 20 127 Methomyl oxime Y .0399 .04037 101 8 Metsulfuron-methyl Y .0071 .00569 80 1

Neburon N .5493 .12373 23 110

Nicosulfuron N 1.5246 .11032 7 305

Norflurazon Y .7425 .06540 9 149 Oryzalin N .4705 .06710 14 94 Oxamyl N .0676 .06188 92 14 Oxamyl oxime Y .4521 .06752 15 90 Propham N .4011 .10534 26 80 Propiconazole N .8118 .16649 21 162 Propoxur N .3371 .13514 40 67

Siduron N .7349 .06842 9 147 Sulfometuron methyl N 1.2940 .10436 8 259

Tebuthiuron N .6379 .05940 9 128

Terbacil Y .3790 .04253 11 76 Tribenuron-methyl Y 1.4160 .00000 0 283ANALYTICAL METHOD 57 Table 31 . Accuracy and precision data from eight determinations of the method compounds fortified at 0.50 microgram per liter in surface-water samples, under negative ionization conditions. Recoveries corrected for ambient compound concentrations listed in table 25

[conc., concentration; Y/N, yes/no; μg/L, microgram per liter; nd, not determined]

Compound Reported as

an estimated

conc. (Y/N) Mean

observed

conc. (μg/L) Standard

deviation

(μg/L) Relative

standard

deviation (percent) Mean

accuracy (percent of true conc.)
2,4-D N 0.4874 0.32028 66 97 2,4-DB N .2254 .15642 69 45

Acifluorfen Y .2168 .16552 76 43

Bentazon N .2014 .12745 63 40 Bromoxynil N .2520 .17770 71 50

Chlorothalonil N nd nd nd nd Clopyralid N .1158 .08788 76 23

Dacthal monoacid N .1428 .11184 78 29

Dicamba N .1913 .13510 71 38 Dichlorprop Y .2376 .16962 71 48

Dinoseb Y .3043 .21623 71 61

MCPA N .2393 .16637 70 48

MCPB Y .2320 .16347 70 46

Picloram N .1385 .08582 62 28 Triclopyr Y .2076 .14622 70 42



### reported as qualified estimates, the corresponding mean recoveries were 103.9 
96.1, 82.9  33.8, and 104.5  91.0 percent at
fortifications of 0.050, 0.100, and 0.500  g/L, respectively. The corresponding medians were 75.0, 87.0, and 84.0 percent.

Furlong and others (2000) have previously noted apparent matrix

enhancement of concentr ation observed in the

0.05- and 0.5-  g/L fortifications in this study. The sample used for these fortifications was

collected about 12 months after the 0.1-  g/L fortification. The appa rent matrix enhancement observed in the surface-water samples also appears to be compound class-specific and is further discussed in a subsequent section (11.5.3) of this report. The fact that

the South Platte River water used for these

fortifications was collected at a different time and location may have a substantial role in determining the type and extent of matrix

effects.

11.4.3 Mean recoveries for compounds reported without qualification and determined by negative ionization in the surface-water samples were lower than in
positive ionization, at 115  188, 69.3  10.4,

and 44.2  21.9 percent, at fortifications of
0.05, 0.100, and 0.500  g/L, respectively. The corresponding median recoveries were 50.0, 71.0, and 40.0 percent, and reflect the higher variablity observed among compounds in negative ionization analysis. The mean recoveries of compounds reported as qualified estimates and determined by negative

ionization in surface water were lower but
less variable, at 51.4  1.3, 72.8  5.8, and

48.0  7.6 percent at fortifications of 0.05,
0.100, and 0.500  g/L, respectively. The corresponding median recoveries were 52.0, 73.5, and 46.0 percent. Th e determination of whether a compound was reported as a qualified estimate was a function of long-term recoveries in reagent water (11.6.2). In this case, matrix effects may have resulted in

lower but less variable recoveries.

11.4.4 Average surface-water

recoveries of all co mpounds at all three

fortification leve ls varied about  65 percent

### for compounds determined by positive

ioniz a tion and  59 percent for compounds determined by neg a tive ioniz a tion. This

vari at i on i ndi cat es t h at t h e accuracy of t h e method in the surface-water samples is compound dependent, and mig ht reflect compound-specific bias resulting from the

surface-wat e r m a t r i x . Underst a ndi ng analy tical precision is equally important to using any analy tical method, however, and

anal y t i cal preci si on i s bet t e r refl ect ed by t h e relative standard devi ation of individual compound recoveries from the surface-water

sa mple s. Unde r positive ioniza tion conditions, the mean relative standarddeviations for all compounds in the surfacewa te r sa mple s we r e 12  9, 15  9, and 27  27 percent for 0.050-, 0.100-, and 0.500- μ g/ L

f o r tif ic a tions, r e spe c tive l y

. The corresponding relative sta ndard deviations for

neg a tive ioniz a tion results were 14  15, 12  6, and 70  5 percent for 0.050-, 0.100-, and

0.500- μ g / L f o r tif ic a tions, r e spe c tive l y

. S u rface-wat e r m a t r i x effect s, part i c ul arl y t h e hig h er DOC concentration in the South Platte River, mig ht be responsible for the

substa ntia lly hig h e r va r i a b ility obse r ve d in the

0.500-  g / L f o r tif ic a tions f o r

both positive a nd

neg a tive ioniz a tion compounds than in the

g r ound-water samples and the org a nic-freewater samples (11.2 and 11.3).

11.5 Compound-specific recovery

r e sults

11.5.1 The method validation

r e sults by c l a ss f o r

a ll thr e e te ste d ma tr ic e s are shown in fig u res 2, 3, 4, and 5. I n fig u res 2, 3, and 4, each fi g u re cont ai ns t h e anal y t i cal results under positive ioniz a tion for one

matrix at three concen trations, subdivided by compound class. The four compound class

g r ouping s were as follows: (A) carbamate

inse c tic ide s ; ( B ) tr ia zine a nd phe ny lur e a he r b ic ide s ; ( C ) sulf ony lur e a
, sulf ona mide

, and imidaz olinone herbicides; and (D)

miscellaneous herbic ides and other compounds. Pesticides determined by

neg a tive ioniz a tion HPL C /MS are g r ouped by

ma tr ix in f i g u r e 5. 11.5.2 A review of the positive

i oni z a t i on resul t s for each m a t r i x (fi g s . 2

thr oug h 4) r e ve a l s c onsiste nt simila r itie s

across m a t r i ces. Two carbamate deg r adation products, ox amy l ox ime and methomy l

ox ime, have poor recove ries (averag e d only 23, 22, and 29 percent in org a nic-free water,

g r ound-water and surf ace-water samples,

r e spe c tive l y ) c o mpa r e d to the r e ma ining

c a r ba ma te inse c tic ide s in whic h r e c ove r i e s

averag ed 87, 82, and 66 percent, respectively

. I n the other g r ouping s, tribenuron was lower

t h an t h e averag e recoveri es for ot her miscellaneous compounds in the org a nic-free water and in the g r ound-water samples. Tribenuron in the org a nic-free water and in the g r ound-water samples averag ed 48 and 57

percent

, respect i v el y , but in contrast, recovery

was apparent l y enhanced i n t h e surface-wat er samples, at 178 percent, althoug h recovery in

surface wat e r vari ed bet w een fort i f i cat i on le ve ls, with the g r e a t e s t va r i a tion me a s ur e d a t the hig h est level (fig

. 4D).

11.5.3 W h en compared with the

org a nic-free water and the g r ound-water

sam p l e s (fi g s . 2 and 3), fort i f i e d surface-wat e r recoveri es were m o re variable, which

indicated that seve ral compound classes

ex perienced apparent enhancement of

recovery . As noted above , this finding applied to tribenuron, but also was observed for the sulfony lurea, sulfonamide, and imidaz olinone

he r b ic ide s . This r e sult is c onsiste nt with apparent matrix enhancement of recovery for sulfony lurea, sulfonamide, and imidaz olinone

herbicides observed in a rang e of naturalwa te r sa mple s a nd Sout h Platte River water (F urlong and others, 2000). The results shown in fig u re 4 sug g e st that enhancement varies by compound class. The car bamate insecticides (fi g

. 4A) appear t o ex peri ence t h e l east enhancement and, for 3-ketocarbofuran, perhaps some suppression of recovery . The

recoveries of the tr iaz i ne and pheny lurea herbicides (fig

. 4B ) are consistent with

recoveri es i n t h e org a ni c-free wat e r and i n t h e

g r ound-water samples (fig s . 2B and 3B ),

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 58ABCD

ANAL Y T I C AL M E T H OD 59Figure2.Recoveries, in percent, forcompoundsfortified at three levelsin organic-free waterand determined underpositive ionization conditions.(A)N-methylcarbamate and related compounds; (B)phenylurea and triazine compounds; (C)sulfonylurea, imidazolinone and relatedcompounds;and (D)otherclassesofcompounds. Errorbarsindicate ±1standard deviation.60 P esti c i d es i n Water by Graphi ti z e d Carbon-Based S P E and HP LC/ M SABDCFigure3.Recoveries, in percent, forcompoundsfortified at three levelsin ground-watersamplesand determined underpositive ionizationconditions. (A)N-methylcarbamate and related compounds; (B)phenylurea and triazine compounds; (C)sulfonylurea, imidazolinone and relatedcompounds; and (D)otherclassesofcompounds. Errorbarsindicate ±1standard deviation.BACD

ANAL Y T I C AL M E T H OD 61Figure4. Recoveries, in percent, forcompoundsfortified at three levelsin surface-watersamplesand determined underpositive ionization conditions. (A)N-methylcarbamate and related compounds; (B)phenylurea and triazine compounds; (C)sulfonylurea, imidazolinone and related compounds; and (D)otherclassesofcompounds. Errorbarsindicate ±1standard deviation.62 P esti c i d es i n Water by Graphi ti z e d Carbon-Based S P E and HP LC/ M SAABBCFigure5. Recoveries, in percent, forcompoundsdetermined undernegativeionization conditions. (A)Compoundsfortified at three levelsinorganic-free water;(B)compoundsfortified at three levelsin ground-watersamples;and (C)compoundsfortified at three levels insurface-watersamples.Errorbarsindicate ±1standard deviation.

### althoug h they are somewhat more variable in

t h e surface-wat e r sam p l e s. R ecoveri es of t h e sulfony lurea, sulfonamide, and imidaz olinone

herbi c i d es (fi g 4C ) are the most enhanced of all the compound classes in the surface-water
samples and averag ed 214  35 percent compared to 108  9 and 134  14 percent in the org a nic-free and in the g r ound-water

sa mple s, r e spe c tive l y

. The misc e lla ne ous compounds are variable, with the most

enhancem ent m easured i n t h e recoveri es of tribenuron, but with si g n ificant enhancement

in the r e c ove r i e s of ima da c l opr id, me ta la x y l,

norfluraz on, and propiconaz o le (fig

. 4D).

Concentrations of compounds determined under neg a tive ioniz a tion conditions (fig

. 5) sug g e st no matrix

enhancement. Recoveri e s we r e ty pic a lly le ss than 100 percent. Recoveries for all compounds at all fortifications averag ed 75.2 ± 9.3, 80.0 ± 6.5, and 45.8 ± 18.8 percent in samples of org a nic-fr ee water, g r ound water,

and surface wat e r, respect i v el y

. C h l o rothalonil was variably a

nd poorly recovered in

a ll ma tr ic e s a nd wa s a substa ntia l inf l ue nc e on the observed recoveries and standard

de via tions in a ll ma tr ic e s (fig

. 5). Recoveries

also were lower and more variable in the

surface-wat e r sam p l e s and m a y refl ect ei t h er matrix interference or suppression of

recovery

.

11.6 L ong -term laboratory reag ent spike r e sults

11.6.1 As noted earlier, fortified

org a ni c-free wat e r or l a borat ory reag ent spi k e (L R S ) sam p l e s were anal y z ed as part of t h e quality control for each environmental sample

se t. The s e L R S sa mple s we r e ma de up f r o m the sa me pe stic ide

- f r e e wa te r use d f

o r

r e a g e n t- wa te r f

o r tif ic a tion r e c ove r y

ex periments and were at concentrations of 0.250 μ g /L for each compound. The L R S

pr ovide s se t- spe c i f i c qua lity

- c ontr o l

i n form at i on for i n t e rp retation of individual

sam p l e s i n t h e set

. W h en ag g r eg at ed (table 32), L R S data al so provide long -term, multiple instr u me nt, a nd multiple ope r a tor performance data. F o r the purposes of determining long -term method performance, results from fiscal y ear 2000 were ag g r eg ated

a nd summa r y

sta tistic s were produced. The

ag g r eg ation was made for fiscal y ear 2000 so

t h at t h e dat a refl ect t h e perform ance of t h e method after implementa tion and training of

t h e chem i s t s who perform t h e anal y s es. A total of 285 reag ent spik es was determined in fiscal y ear 2000.

11.6.2 L ong -term L R S recoveries

averag ed 73.8 percent for all compounds, with an averag e standard deviation of 24.2

percent

. The averag e m e di an recovery for al l compounds was similar to the mean, at 73.4

percent

, and t h e averag e f -pseudosig ma of

recovery was 21.4 percent. All compounds in the method ranked according to increasing mean recoveries are shown in fig u re 6.

Two sta tistic s we r e use d to
de te r mine if the r e por te d concentration of any compound required quantita tion qualification.

Medi an recoveri es cal cul a t e d from l ong -t erm
L R S data are used to estimate the accuracy of concentration. A nonpara metric statistic, f

pseudosig ma (Hoag lin, 1983) is calculated to

de te r mine the va r i a tion of L R S recoveries.

These st at i s t i c s are used i n st ead of t h e m e an and standard deviation because they minimiz e the e f f e c t s of outlie r va lue s , a nd a r e thus mor e representative of long -term method performance under multiple operators and

instruments. Median recoveries had to fall within 60 and 120 percent for a compound to be considered reportabl e without qualification.

I n addition, the f -pseudosig ma statistic had to be less than 25 percent for a compound to be reported without qualification.

Median recoveries and the f

pseudosig ma statistics for those recoveries were

c a l c u la te d f o r

se t L R S da ta de te r mine d be twe e n October 1, 1999, and September 31, 2000. This

dat a peri od was used because i t was consi d ered representative of method performance after the

AN AL Y T I C AL M E T H O D 63T a b l e 32. Long- ter m ac c u r a c y and pr ec is ion c a lc ulated f r om m u ltiple deter m i nations of the m e thod c o m pounds

f o r t if ied in s a m p le- s et s p ik es w i th the c o m pounds added to or ganic

- f r ee w a ter at 0.25 m i c r ogr am per liter

[N, n u m ber of determ in ation s ]

C o m p o u n d N Number

of

missin g

v a lu es M ean

reco v e ry ( p ercen t ) S t a nda r d

de v i a t ion

of

reco v e ry ( p ercen t ) Me d i a n

reco v e ry ( p ercen t ) F

ps e udos igma

o f

reco v e ry ( p ercen t ) M i nimum

reco v e ry ( p ercen t ) M aximum

reco v e ry ( p ercen t )

Com p ounds reported w i thout qua lification (M edian Recovery betw een 60 and 120 percent and f

- p se udo sig m a
les s than 25 percent)

2,4- D 2 8 1 4 1 0 1

. 8 4 3

. 6 1 0 2

. 0 1 6

. 3 0

. 1 7 5 4
2,4- D m e t h y l es t e r 282 3 83.5 19.3 84.5 15.4 0.1 150
3(4- ch l o roph en y l )- 1- m e t h y l u r ea 282 3 95.5 14.8 96.0 9.5 0.1 155

3- H y drox y carbof u r an 2 8 2 3 9 1

. 7 1 8

. 7 9 2

. 0 1 2

. 6 0

. 1 1 7 8

A c i f l u orf e n 2 8 0 5 8 4

. 0 2 0

. 2 8 6

. 0 1 8

. 5 0

. 0 1 3 4

A t razi n e 2 8 2 3 7 4

. 4 1 9

. 3 7 7

. 0 1 6

. 3 0

. 1 1 3 5

Ben d i o c a r b 2 8 2 3 7 5

. 8 2 1

. 1 7 9

. 0 1 2

. 6 0

. 1 1 5 4

Ben o m y l 2 8 0 5 8 9

. 0 2 2

. 9 9 0

. 0 1 3

. 5 0

. 0 1 6 9

Ben s u l f u ron

- m e t h y l 2 8 2 3 9 7

. 2 2 2

. 0 9 5

. 0 1 3

. 3 0

. 0 1 7 7

C a f f e i n e 2 8 2 3 1 0 1

. 2 2 3

. 5 1 0 3

. 5 2 0

. 6 0

. 1 1 7 2

C a rbary l 2 8 2 3 8 7

. 7 1 7

. 1 8 9

. 0 9

. 5 0

. 0 1 7 3

C a rbof u r an 2 8 2 3 9 0

. 7 1 6

. 1 9 0

. 0 9

. 6 0

. 1 1 6 6

C h l o ri m u ron

- et h y l 2 8 2 3 1 0 2

. 6 2 6

. 3 1 0 1

. 5 1 9

. 1 0

. 0 1 7 9

C l opy ral i d 2 8 1 4 7 8

. 8 1 7

. 9 8 0

. 0 1 4

. 8 0

. 0 1 1 7

D act h a l m o n o aci d 279 6 82.1 14.3 83.0 14.1 0.1 115

D i cam b a 2 8 1 4 8 8

. 8 1 9

. 6 8 9

. 0 1 7

. 8 0

. 0 1 4 4

D i ch l o r p r o p 2 8 0 5 7 5

. 5 1 5

. 0 7 8

. 0 1 4

. 8 0

. 1 1 0 6

D i n o s e b 2 8 1 4 8 0

. 0 2 1

. 6 7 9

. 0 2 1

. 5 0

. 0 1 3 9

D i ph en am i d 2 8 2 3 8 3

. 4 1 6

. 2 8 4

. 0 1 1

. 7 0

. 1 1 5 8

D i u r on 2 8 2 3 8 9

. 8 1 5

. 5 9 0

. 0 9

. 6 0

. 1 1 6 0

F e n u r on 2 8 2 3 7 3

. 6 1 9

. 5 7 5

. 0 2 1

. 3 0

. 0 1 4 5

F l u o m e t u ron 2 8 2 3 8 5

. 7 1 4

. 9 8 6

. 0 1 1

. 1 0

. 1 1 5 5

Im i d acl opri d 2 8 2 3 1 0 6

. 2 2 2

. 7 1 0 6

. 5 1 9

. 3 0

. 1 1 7 8

L i n u r on 2 8 2 3 8 9

. 5 1 6

. 7 9 1

. 0 1 1

. 1 0

. 1 1 5 4

MC PA 2 8 1 4 7 0

. 5 1 8

. 6 7 2

. 0 1 4

. 8 0

. 1 1 5 6

Met a l a x y l 2 8 2 3 8 5

. 8 3 9

. 5 8 4

. 0 9

. 6 0

. 1 7 0 1

N e bu ron 2 8 1 4 8 9

. 8 1 8

. 2 9 2

. 0 9

. 6 0

. 1 1 6 0

N i cos u l f u r on 2 8 2 3 1 0 3

. 9 2 7

. 7 1 0 3

. 5 2 2

. 2 0

. 1 2 0 5

O r y zal i n 2 8 2 3 8 0

. 7 1 7

. 9 8 1

. 0 1 4

. 1 0

. 1 1 5 0

O x am y l 2 8 2 3 6 4

. 1 1 9

. 4 6 6

. 0 1 6

. 9 0

. 0 1 4 4

Pi cl oram 2 8 1 4 8 8

. 7 1 7

. 4 8 9

. 0 1 5

. 6 0

. 0 1 3 0
Proph am 2 8 2 3 9 0

. 9 1 6

. 3 9 0

. 0 1 3

. 3 0

. 1 1 6 1
Propi con azol e 2 8 1 4 1 0 2

. 4 2 0

. 2 1 0 5

. 0 1 4

. 1 0

. 1 1 5 7
Propox u r 2 8 2 3 8 3

. 6 1 4

. 2 8 5

. 0 1 1

. 1 0

. 1 1 2 6

S i du ron 2 8 2 3 8 0

. 3 2 1

. 0 8 3

. 0 2 3

. 0 0

. 1 1 4 8

S u l f om et u r on

- m et h y l 2 8 2 3 8 5

. 5 2 1

. 6 8 8

. 0 1 5

. 6 0

. 0 1 4 8

T e bu t h i u ron 2 8 2 3 1 0 0

. 4 1 6

. 1 1 0 1

. 0 1 1

. 1 0

. 1 1 7 2

T r i c l opy r 2 8 1 4 8 3

. 2 1 6

. 7 8 5

. 0 1 4

. 1 0

. 1 1 3 6

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 64T a b l e 32. Long- ter m ac c u r a c y and pr ec is ion c a lc ulated f r om m u ltiple deter m i nations of the m e thod c o m pounds f o r t if ied in

s a m p le- s et s p ik es w i th the c o m pounds added to or ganic

- f r ee w a ter at 0.25 m i c r ogr am per liter —Continued

C o m p o u n d N Number

of

missin g

v a lu es M ean

reco v e ry ( p ercen t ) S t a nda r d

de v i a t ion

of

reco v e ry ( p ercen t ) Me d i a n

reco v e ry ( p ercen t ) F

ps e udos igma

o f

reco v e ry ( p ercen t ) M i nimum

reco v e ry ( p ercen t ) M aximum

reco v e ry ( p ercen t )

Co m p o unds qua lified w i th a n E-co de beca use bia s w a s o u tside a ccepta ble ra ng e (m ed ian recovery les s th an 60 p ercen t or greater th an 120 p ercen t)

2,4- D B 2 8 1 4 5 3

. 1 1 5

. 0 5 5

. 0 1 2

. 6 0

. 1 9 9

3- K e t o carbof u r an 2 8 2 3 4 4

. 7 2 8

. 5 4 1

. 5 3 2

. 6 0

. 0 1 1 2

A l di c a r b 2 8 1 4 1 1

. 4 1 5

. 5 4

. 0 1 3

. 3 0

. 0 6 6

A l di carb s u l f on e 279 6 55.2 18.9 59.0 17.0 0.0 109

A l di carb s u l f ox i d e 271 14 30.5 27.8 26.0 37.8 0.0 113

Ben t azon 2 7 8 7 3 8

. 6 3 5

. 4 2 5

. 0 4 3

. 6 0

. 0 1 2 1

Brom ox y n i l 2 8 1 4 6 0

. 3 6 1

. 4 5 2

. 0 5 1

. 9 0

. 1 8 9 0

C h l o ram b en m e t h y l es t e r 275 10 56.2 30.7 57.0 37.1 0.0 157

C h l o rot h al on i l 2 8 1 4 2 0

. 1 2 1

. 2 1 7

. 0 2 5

. 2 0

. 0 8 0

C y cl oat e 2 7 7 8 3 8

. 2 3 0

. 7 3 1

. 0 4 0

. 8 0

. 0 1 2 3

F l u m et s u l a m 2 8 2 3 1 3 0

. 0 3 4

. 8 1 2 8

. 5 3 4

. 8 0

. 1 2 1 2

Im azaqu i n 2 7 7 8 1 2 3

. 0 3 6

. 9 1 2 4

. 0 2 6

. 7 0

. 1 2 5 9

MC P B 2 8 1 4 5 5

. 9 4 2

. 8 5 6

. 0 1 3

. 3 0

. 1 7 2 5

Met h i o c a r b 2 8 2 3 4 1

. 6 3 6

. 6 3 0

. 0 5 3

. 9 0

. 0 1 5 9

Met h om y l 2 8 2 3 4 3

. 2 3 2

. 9 3 9

. 0 4 6

. 0 0

. 0 1 5 2

Met h om y l ox i m e 281 4 3.3 4.0 3.0 4.4 0.0 24

Met s u l f u ron

- m e t h y l 2 8 2 3 2 5

. 3 3 0

. 7 1 1

. 0 3 1

. 9 0

. 0 1 0 5

O x am y l ox i m e 271 14 10.3 9.9 10.0 11.9 0.0 65

T r i b en u r on

- m et h y l 2 7 8 7 6

. 1 1 2

. 2 0

. 0 5

. 9 0

. 0 1 1 7

Co m p o unds qua lified w i th a n E-co de beca us e v a r ia tio n w a s o u tside a ccepta ble ra ng e ( f

-ps e udos i gm a great er than 25 percent)

2- H y drox y a t r azi n e 2 8 2 3 1 0 2

. 6 3 3

. 1 1 0 0

. 0 2 8

. 2 0

. 2 2 1 3

Brom aci l 2 8 2 3 6 7

. 7 4 7

. 5 6 8

. 0 3 6

. 1 0

. 1 6 9 1

D eet h y l a t r azi n e 2 8 2 3 6 9

. 2 2 7

. 7 6 9

. 0 3 0

. 9 0

. 1 1 3 2

D eet h y l d ei s opropy l a t r azi n e 2 8 2 3 6 4

. 7 2 6

. 5 6 2

. 5 3 1

. 1 0

. 1 1 7 9

D e i s opropy l a t r azi n e 2 8 2 3 6 7

. 3 2 9

. 2 6 7

. 0 3 0

. 4 0

. 1 1 4 9

Im azeth a py r 2 2 9 5 6 1 1 3

. 5 5 4

. 3 1 1 5

. 0 3 5

. 6 0

. 0 3 3 6

N o rf l u razon 2 8 2 3 6 9

. 9 2 4

. 4 7 3

. 0 2 8

. 9 0

. 1 1 5 4

T e rbaci l 2 8 2 3 6 5

. 7 3 1

. 7 7 0

. 5 4 0

. 8 0

. 1 1 4 1



### method had been implement ed and the operators

of the method ex perienced in its use. The results

of these calculations are listed in table 32. Median recoveries for all compounds are plotted in fig u re 6 to provide a r e f e r e nc e se t of ty pic a lly

accept a bl e perform ance. Medi an recovery and f

pseudosig ma limits are used as a g u ide, thereby resulting in 27 compounds reported as qualified

c onc e n tr a tion e s tima te s.

Of these 27 compounds, nine are pesticide deg r adates. Two compounds,

flumetsulam and imaz a quin, had median recoveries g r eater than 120 percent. These two compounds are known to ex perience

ma tr ix e nha nc e m e n t of concent r at i on when

de te r mine d with a c o mple te ly dif f e r e nt SPE isolation method and by positive ion electrospray HPL C /MS (F urlong and others, 2000). Althoug h there should be no

ma tr ix pr e s e n t in the s e se t f o r tif ic a tion

sa mple s, it is possible tha t ma tr ix

carry over, or minor amounts of matrix

cont am i n at i on t h at resul t from l eachi n g from the Carbopack SPE phase, mig ht

r e sult in ma tr ix e nha nc e m e n t.

AN AL Y T I C AL M E T H O D 6566 P esti c i d es i n Water by Graphi ti z e d Carbon-Based S P E and HP LC/ M SFigure6.Median recoveriesofmethod compoundsfrom285 laboratoryreagent spikesdeterminedfromOctober1, 1999 to September30, 2000. Errorbarsare fromthef-pseudosigmastatistic.

### F o r these 27 compounds, recoveries averag ed 55.5 percent for all compounds, with an

averag e standard deviation of 29.7 percent. The averag e m e di an recovery for al l com

pounds was similar to the mean, at 53.5

percent

, and t h e averag e f -pseudosig ma of

recovery was 30.4 percent.

The remaining 38 compounds met

recovery perform ance cri t e ri a and were reported without qualification. F o r these compounds, recoveries averag ed 87.3 percent for all compounds, with an averag e standard deviation of 20.1 percent. The averag e median recovery for all compounds was similar to the mean, at 88.2 percent, and the

averag e f -pseudosig ma of recovery was 14.7

percent

.

11.7 L a boratory reag ent blanks

A total of 498 L R B s was analy z ed while this method was used as a provisional custom

method. A subset of 197 L R B s was reviewed in

de ta il to de te r mine the f r e que nc ie s a nd concentrations of possibl e blank contamination. These results are listed in table 33. Twenty

eig h t of 65 compounds measured in this method

were detected in the set blanks. Ex cept for

T a b l e 33. Detec t ions of c o m pounds in 197 s e t blank s analy z ed w i th this m e thod

[μg / L

, m i cro g ram p e r liter]

Compound Number of

de te c t ions M ean

co n cen t r at io n , in μg/L Me d i a n

co n cen t r at io n , in μg/L
2,4- D m e t h y l es t e r 1 0.0166 0.0166

2- H y drox y a t r azi n e 1

. 0 4 1

. 0 0 4 1
3(4- ch l o roph en y l )- 1- m e t h y l u r ea 1 .0018 .0018

3- H y drox y carbof u r an 2

. 0 0 1 4

. 0 0 1 4

A t razi n e 4

. 0 0 1 6

. 0 0 1 4

Ben d i o c a r b 1

. 0 0 0 4

. 0 0 0 4

Ben o m y l 1

. 0 0 1 8

. 0 0 1 8

Brom aci l 1

. 0 0 8 9

. 0 0 8 9

C a f f e i n e 3

. 0 0 5 9

. 0 0 5 7

C a rbary l 2

. 0 0 2 3

. 0 0 2 3

C y cl oat e 4

. 0 1 0 9

. 0 1 0 6

D eet h y l a t r azi n e 2

. 0 0 1 1

. 0 0 1 1

D eet h y l d ei s opropy l a t r azi n e 1

. 0 0 1 5

. 0 0 1 5

D i n o s e b 5

. 0 0 1 1

. 0 0 1 1

D i ph en am i d 1

. 0 0 0 7

. 0 0 0 7

D i u r on 6

. 0 1 0 9

. 0 0 4 7

F e n u r on 3 8

. 0 1 1 6

. 0 0 5 9

F l u o m e t u ron 4

. 0 0 1 8

. 0 0 2 0

Im azaqu i n 7

. 0 0 5 4

. 0 0 7 3

Im azeth a py r 3

. 0 2 9 5

. 0 2 9 8

Met a l a x y l 2

. 0 0 0 6

. 0 0 0 6

Met h i o c a r b 2

. 0 2 7 5

. 0 2 7 5

N e bu ron 3

. 0 0 1 3

. 0 0 1 1

N o rf l u razon 5

. 0 0 1 8

. 0 0 1 4
Propi con azol e 1 2

. 0 0 1 1

. 0 0 1 1

S i du ron 1

. 0 0 1 4

. 0 0 1 4

S u l f om et u r on

- m et h y l 5

. 0 0 3 6

. 0 0 4 1

T e bu t h i u ron 6

. 0 0 1 6

. 0 0 1 5

M E T H O D AN AL Y S I S 6 7

### fenuron, the frequency of detections rang ed

from 1 to 12 in 197 blanks. The median frequency of detection in all blanks, ex cept for fenuron, was 2.5 detec tions. Detections

were clustered in 38 bla nk sa mple s. I n tota l, 93 detections of all compounds were measured, a rate of 0.73 percent, calculated on the basis of 12,805 individual compound determinations made for 65 compounds in 197 blank samples.

One compound, imaz e thapy r , was de te c t e d one time a t a c onc e n tr a tion g r e a t e r than its median met hod laboratory reporting level (L RL is calculated as twice the method detection limit; see section 11.8). Only 11 of the method analy t es detected were at concentrations g r eater than 0.0025 μg /L . F o r these 11 compounds (sulfometuron-methy l

, norfluraz on, methiocarb, imaz e thapy r
, imaz a quin, diuron, cy cloate, caffeine,

bromox y n il, 2-hy drox y a traz ine, 2,4-D), the

median detected concentration was 0.0018

μg /L

.

F e nuron was determined in 38 of 197 blanks, a rate of 19 pe rcent, and was the only compound identified frequently enoug h to be

consi d ered a chroni c cont am i n ant for t h e method. I t is unclear whether this chronic

contamination was a re sult of actual fenuron contamination or the result of a coeluting

i n t e rference t h at cont ri buted ions that were

i d ent i cal t o t hose used for t h e sel ect ed-i on monitoring determina tion of fenuron. F o r chronic contamination of this ty pe, the

statistics of the distribution should be

c a l c u la te d, the 95th pe r c e n tile of the distribution determined, a nd the r e sult use d to qualify detections in f

i e l d sa mple s.

11.8 Method detection limits

11.8.1 Method detection limits (MDL s) were determined for this method using the procedures of the U.S. Environmental Protection Ag ency (1997).

Da ta f

o r

the MDL de te r mina tion we r e f o r

the

lowest concentration of f o r tif ic a tion use d to determine method recoveries (0.025  g / L for the org a nic-free samples and the g r oundwater samples, and 0.05  g / L for t h e surfacewat e r sam p l e s). The cal cul a t e d MDL s are listed in table 34. The MDL s calculated for the predecessor method of W e rner and others (1996) are also listed in table 34. The

ex traction part of this method is based on that report. There are 30 compounds in the present method that are not included in the method by W e rner and others; the latter

contains six compounds not in the present

method. These ex ceptions are listed separately at the bottom of table 34.

11.8.2 On averag e, the MDL s for both methods were comparable. The mean

MDL s for all compounds in the present method were 0.019 ± 0.090, 0.007 ± 0.012, and 0.017 ± 0.010 μ g /L for the org a nic-free

water, g r ound-water, and surface-water

sam p l e s, respect i v el y

. The m ean MDL s for all compounds in the method by W e rner and others (1996) were 0.014 ± 0.006, 0.018 ± 0.009, and 0.029 ± 0.023 μg /L for org a nicfree water, g r ound-water, and surface-water

sa mple s, r e spe c tive l y

. The me dia n MDL s f o r the present method were 0.007, 0.003, and 0.014 μ g /L for the org a nic-free water,

g r ound-water, and surf ace-water samples,

respect i v el y

. These MDL s com p are favorably with median MDL s of 0.007, 0.009, and 0.026 μ g /L for org a nic-free water,

g r ound-water, and surf ace-water samples, respectively

, in the method by W e rner and others (1996). The mean MDL for all analy t es in the present method, reg a rdless of
long -term performance, was 0.033  g/ L

.

11.8.3 I f the comparison of MDL s is limited to the 35 compounds common to both methods, the data sug g e st that this new method offers improved detection at lower

concentrations. I n the new method, the mean

MDL s for the 35 compounds were 0.008 0.004, 0.004 0.002, and 0.016 0.011  g/ L for org a nic-free water, g r ound-water, and

surface-wat e r sam p l e s, respect i v el y

.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 68T a b l e 34. Method detec tion lim its f o r the m e thod des c r ibed in this s t udy and the pr edec es s o r m e thod of

W e r ner and other s ( 1996)

[Co n cen tratio n s in m i cro g ram p e r liter (μg / L ) . MDL

, m e th o d d e tectio n lim it; n d , n o t d e term in ed ]

Compound Th i s

me thod,

MD L i n

or ga nic

f r ee

wa t e r We r n e r

me thod,

MD L i n

or ga nic

f r ee

wa t e r 1 Th i s

me thod,

MD L i n

gr oundwa t e r

samp l es We r n e r

me thod,

MD L i n

gr oundwa t e r

samp l es 1 Th i s

me thod,

MD L i n

su rf acewa t e r

samp l es We r n e r

me thod,

MD L i n

su rf acewa t e r

samp l es 1

2,4- D 0

. 0 1 0 9 0

. 0 1 3 0

. 0 0 5 7 0

. 0 2 3 0

. 0 4 6 3 0

. 0 2 1

2,4- D B

. 0 0 8 0

. 0 1 3

. 0 0 5 5

. 0 1 5

. 0 0 9 1

. 0 1 2

3- H y drox y carbof u r an

. 0 0 2 9

. 0 1 4

. 0 0 7 4

. 0 1 5

. 0 1 7 1

. 0 2 6

A c i f l u orf e n

. 0 0 3 3

. 0 0 8

. 0 0 4 3

. 0 2 1

. 0 0 9 4

. 0 2 2

A l di c a r b

. 0 1 9 8

. 0 1 6

. 0 0 3 6

. 0 1 4

. 0 2 1 7

. 0 2 0

A l di carb s u l f on e .0098 .021 .0028 .016 .0227 .037

A l di carb s u l f ox i d e .0041 .016 .0023 .019 .0056 .043

Ben t azon

. 0 0 5 5

. 0 1 4

. 0 0 3 2

. 0 2 2

. 0 1 3 0

. 0 2 9

Brom aci l

. 0 1 6 3

. 0 1 1

. 0 0 3 3

. 0 4 0

. 0 1 0 2

. 0 5 0

Brom ox y n i l

. 0 0 8 5

. 0 1 2

. 0 0 6 0

. 0 1 1

. 0 1 5 5

. 0 1 1

C a rbary l

. 0 1 4 2

. 0 0 8

. 0 0 2 0

. 0 1 8

. 0 1 5 4

. 0 1 6

C a rbof u r an

. 0 0 2 8

. 0 2 8

. 0 0 2 5

. 0 2 8

. 0 1 0 3

. 0 4 4

C h l o ram b en m e t h y l es t e r .0089 .011 .0032 .011 .0141 n d

C h l o rot h al on i l

. 0 1 7 3

. 0 0 7

. 0 0 8 8

. 0 1 2 n d

. 0 2 1

C l opy ral i d

. 0 0 6 9

. 0 1 8

. 0 0 3 4

. 0 0 7

. 0 0 3 7

. 0 2 3

D act h a l m o n o aci d .0058 .017 .0029 .035 .0272 .024

D i cam b a

. 0 0 6 4

. 0 1 1

. 0 0 2 7

. 0 2 5

. 0 0 3 6

. 0 2 1

D i ch l o r p r o p

. 0 0 6 9

. 0 3 2

. 0 0 5 2

. 0 1 8

. 0 0 9 6

. 0 4 3

D i n o s e b

. 0 0 6 0

. 0 1 0

. 0 0 2 8

. 0 3 2

. 0 0 6 1

. 0 1 3

D i u r on

. 0 0 7 5

. 0 1 2

. 0 0 1 8

. 0 1 2

. 0 1 9 6

. 0 4 0

F e n u r on

. 0 1 5 8

. 0 1 3

. 0 0 3 2

. 0 1 7

. 0 2 2 4

. 0 6 7

F l u o m e t u ron

. 0 1 5 5

. 0 1 0

. 0 0 2 1

. 0 1 0

. 0 1 1 3

. 0 3 8

L i n u r on

. 0 0 7 2

. 0 0 6

. 0 0 3 4

. 0 1 6

. 0 2 0 6

. 0 2 4

MC PA

. 0 0 8 1

. 0 1 4

. 0 0 3 2

. 0 0 9

. 0 1 1 0

. 0 1 6

MC P B

. 0 0 7 7

. 0 1 0

. 0 0 3 2

. 0 0 9

. 0 1 0 1

. 0 3 8

Met h i o c a r b

. 0 0 4 0

. 0 2 6

. 0 0 3 1

. 0 1 5

. 0 1 6 7

. 0 5 8

Met h om y l

. 0 0 2 2

. 0 1 7

. 0 0 3 6

. 0 0 8

. 0 1 7 7

. 0 4 7

N e bu ron

. 0 0 6 0

. 0 1 5

. 0 0 3 2

. 0 1 5

. 0 1 4 6

. 0 4 4

N o rf l u razon

. 0 0 8 2

. 0 2 4

. 0 0 2 1

. 0 1 4

. 0 1 2 0

. 0 2 4

O r y zal i n

. 0 0 8 8

. 0 1 9

. 0 0 5 4

. 0 0 8

. 0 4 8 8

. 0 4 2

O x am y l

. 0 0 6 1

. 0 1 8

. 0 0 4 4

. 0 0 8

. 0 3 7 4

. 0 4 2

Pi cl oram

. 0 0 9 9

. 0 0 4

. 0 0 3 3

. 0 1 1

. 0 0 9 8

. 0 2 2
Proph am

. 0 0 4 8

. 0 1 1

. 0 0 2 1

. 0 1 1

. 0 1 8 4

. 0 2 1

Propox u r

. 0 0 4 0

. 0 0 8

. 0 0 2 3

. 0 3 3

. 0 0 7 8

. 0 2 7

T r i c l opy r

. 0 1 1 2

. 0 1 0

. 0 0 3 8

. 0 0 7

. 0 0 4 3

. 0 2 1

AN AL Y T I C AL M E T H O D 6 9T a b l e 34. Method detec tion lim its f o r the m e thod des c r ibed in this s t udy and the pr edec es s o r m e thod of

W e r ner and other s ( 1996) —Continued

Compound Th i s

me thod,

MD L i n

or ga nic

fr e e w a te r We r n e r

me thod,

MD L i n

or ga nic

f r ee

wa t e r 1 Th i s

me thod,

MD L i n

gr oundwa t e r

samp l es We r n e r

me thod,

MD L i n

gr oundwa t e r

samp l es 1 Th i s

me thod,

MD L i n

su rf acewa t e r

samp l es We r n e r

me thod,

MD L i n

su rf acewa t e r

samp l es 1

Co m p o unds a n a l y zed in t h e present m e t h o d o n ly

2,4- D m e t h y l es t e r 0.0043 0.0049 0.0177

2- H y drox y a t r azi n e

. 0 0 4 0

. 0 0 4 5

. 0 1 4 6 3(4- ch l o roph en y l )- 1- m e t h y l u r ea .0121 .0034 .0124

3- K e t o carbof u r an

. 0 0 7 1

. 0 9 6 4

. 0 0 1 5

A t razi n e

. 0 0 4 5

. 0 0 2 8

. 0 1 3 5

Ben d i o c a r b

. 0 1 2 6

. 0 0 3 5

. 0 1 4 7

Ben o m y l

. 0 0 1 9

. 0 0 4 7

. 0 1 3 5

Ben s u l f u ron

- m e t h y l

. 0 0 7 9

. 0 1 0 8

. 0 2 4 6

C a f f e i n e

. 0 0 4 8

. 0 0 1 9

. 0 3 4 6

C h l o ri m u ron

- et h y l

. 0 0 4 8

. 0 0 4 8

. 0 3 2 0

C y cl oat e

. 0 0 6 5

. 0 0 9 7

. 0 1 9 8

D eet h y l a t r azi n e

. 0 1 4 1

. 0 0 2 9

. 0 0 9 9

D eet h y l d ei s opropy l a t r azi n e

. 0 2 2 2

. 0 0 1 9

. 0 0 9 3

D e i s opropy l a t r azi n e

. 0 0 5 2

. 0 0 2 9

. 0 1 0 0

D i ph en am i d

. 0 1 3 2

. 0 0 4 2

. 0 1 2 6

F l u m et s u l a m

. 0 0 5 7

. 0 0 9 6

. 0 2 8 4

Im azaqu i n

. 0 0 7 8

. 0 3 0 6

. 0 2 0 9

Im azeth a py r

. 0 0 8 4

. 0 0 6 0

. 0 4 4 7

Im i d i c l opri d

. 0 0 3 4

. 0 1 0 1

. 0 3 8 3

Met a l a x y l

. 0 1 0 0

. 0 0 2 9

. 0 1 2 2

Met h om y l ox i m e .0053 .0031 .0053

Met s u l f u ron

- m e t h y l

. 0 1 2 3

. 0 1 7 2

. 0 1 4 6

N i cos u l f u r on

. 0 0 6 5

. 0 1 0 4

. 0 3 8 0

O x am y l ox i m e .0067 .0158 .0106 Propi con azol e

. 0 1 0 5

. 0 0 5 0

. 0 1 6 3

S i du ron

. 0 0 8 4

. 0 0 2 9

. 0 1 4 3

S u l f om et u r on

- m et h y l

. 0 0 4 4

. 0 0 9 2

. 0 2 1 0

T e bu t h i u ron

. 0 0 3 1

. 0 0 8 6

. 0 1 4 1

T e rbaci l

. 0 0 4 9

. 0 0 2 0

. 0 1 1 2

T r i b en u r on

- m et h y l

. 0 0 4 4

. 0 0 6 4

. 0 2 1 6

Com p ounds analyzed in the m e thod of Werner and others ( 1996) but not determ ined in the pres ent m e thod

1- N a ph t h ol 0

. 0 0 7 0

. 0 2 3 0

. 0 2 7 2,4,5- T

. 0 1 0

. 0 3 7

. 0 2 7

D i ch l oben i l

. 0 1 2

. 1 2

. 1 6

DNOC

. 0 0 6

. 0 1 5

. 0 1 1

Es f e n v a l e rat e

. 0 1 9

. 0 3 3

. 0 3 9

S i l v ex

. 0 2 1

. 0 2 1

. 0 1 5

1 Wern er, S

. L ., Bu rk h a rdt

, M.R ., an d D e R u s s eau , S

. N ., 1996, Met h ods of an al y s i s by t h e U

. S

. G e ol og i cal S u rv ey Nation a l W a ter Qu ality L a boratory

— Determ in ation of pes tic ides in w a ter by C a rbopak

- B s o lid- p h a s e ex traction an d

h i g h

- perf orm a n ce l i q u i d ch rom a t o g r aph y : U

. S

. G e ol og i cal S u rv ey O p en

- F i l e R e port 96- 216, 42 p.

P esti c i d es i n W a ter by Graphi ti z e d Carbon-Based S P E and HP LC/ M S 70

### The mean MDL s for the same compounds in the method by W e rner and others (1996) were

0.014 0.006, 0.017 0.009, and 0.031

0.014  g / L for org a nic-free water, g r oundwat e r, and surface-wat e r sam p l e s, respect i v el y

. The m e di an MDL s of t h e common compounds for the present method
were 0.008, 0.003, and 0.014  g / L for t h e

org a nic-free water, g r ound-water, and

surface-wat e r sam p l e s, respect i v el y

. These compare favorably with median MDL s of
0.006, 0.009, and 0.026  g / L for org a ni c-free

water, g r ound-water, and surface-water samples, respectively

, in the method by

W e rner and others (1996).

The di fference bet w een t h e m ean and standard deviations for all compounds in

relation to mean and st andard deviations for the compounds common to both methods is likely the result of the additional compounds in the present method being more difficult to isolate, more subject to deg r adation during sample preparation, or more difficult to

resol v e chrom a t o g r aphi cal l y . These effect s would likely introduce additional variation to

t h e concent r at i ons m easured. The MDL s for these difficult compounds would be g r eater than for the compounds common to both

methods because the MDL determination is a

function of standard deviation. The method

doc ume n te d in this r e por t is like l y to r e sult in more frequent detections at com p arabl e or lower concentrations than the method of

W e rner and others (1996), g i ven that

HP L C / M S offers m o re speci fi c det ect i on i n the pr e s e n c e of ma tr ix inte r f e r e nc e s tha n doe s
HPL C with ultraviolet detection.

CONCLUS IONS

Solid-phase ex traction coupled with hig h -performance liquid chromatog r aphy /

m a ss spect rom e t r y

(HP L C / MS ) anal y s i s can be used to determin e and quantify 65 polar

pest i c i d es and pest i c i d e deg r adat es i n surfaceand g r ound-water samples, at concentrations

as low as 0.002  g / L ( mic r o g r a m pe r lite r ) in environmental water sa mples. This method has comparable or be tter method detection

limits tha n the e x isting c o mple me nta r y method of W e rner and others (1996), with the additional advantag e that 65 compounds from 25 pest i c i d e cl asses are m e asured com p ared to 40 compounds in 15 pesticide classes in the

W e rner method. The sing le-operator mean standard deviation at 0.025 μg /L in org a nicf r e e wa te r sa mple s is 11 percent. Recoveries

i n org a ni c-free wat e r sam p l e s rang ed from 28 to175 percent, with elevated recoveries

refl ect i n g apparent m a tr ix e nha nc e m e n t, likely from elevated dissolved org a nic carbon

c onc e n tr a tions. The multiple ope r a tor ( f i ve )

, multiple instr u me nt ( f i ve ) me a n r e la tive

standard deviation is 24.2 percent for all compounds in 285 org a nic-free water samples fortified at 0.25 μg /L and analy z ed for 1 y ear from October 1999 throug h September 2000.

Me a n r e c ove r i e s in the s e sa me sa mple s we r e 73.8 percent for all compounds. The mean long

- t e r m se t f o r tif ic a tion recovery of the 38 compounds in the method reported without qualification rang ed between 60 and 120 percent. An interference corresponding to the

c h r o ma tog r a phic a nd ma ss spe c t r o me tr ic

charact eri s t i c s of fenuron was i d ent i f i e d as a

chroni c cont am i n ant and required qualified reporting of this compound. Eleven compounds were detected sporadically in blanks at concentrations g r eater than 0.025

 g / L

. The sing le operator, sing le instrument

va lida tion da ta a nd the long

- t e r m qua lity

control data reported here provide strong

evi d ence for t h e appl i cat i on of HP L C / M S t o larg e-scale, routine monitoring prog rams for pesticides in surface and g r ound water at

c onc e n tr a tions a s low a s 10 pa r t s pe r tr illion
(0.010  g / L or 10 ng /L ).

CONCL US I O NS 71

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RE F E RE NCE S CI T E D 73