9.10

9.11

concentration. If the accuracy of any analyte falls outside the designated
range, and the laboratory performance for that analyte is shown to be in
control in the LFB, the recovery is judged to be matrix biased. The result for
that analyte in the unfortified sample is labeled suspect/matrix to inform the
data user that the results are suspect due to matrix effects.

FIELD DUPLICATES (FD1 AND FD2) — Within each extraction batch, a minimum
of one Field Duplicate (FD) or LFMD (Sect. 9.9) must be analyzed. FDs check the
precision associated with sample collection, preservation, storage, and laboratory
procedures. If target analytes are not routinely observed in field samples, a LFMD
(Sect. 9.10) should be analyzed to substitute for this requirement. Extraction batches
that contain LFMDs will not require the analysis of a Field Duplicate.

9.10.1 Calculate the relative percent difference (RPD) for duplicate measurements
(FD1 and FD2) using the equation

_ _FDI-FD2_,
(FD1+ FD2)/2

9.10.2 RPDs for duplicates should be in the range of + 30%, Greater variability may
be observed when analyte concentrations are near the MRL. At the MRL,
RPDs should fall in the range of + 50%. If the accuracy of any analyte falls
outside the designated range, and the laboratory performance for that analyte
is shown to be in control in the LFB, the recovery is judged to be matrix
biased. The result for that analyte in the unfortified sample is labeled
suspect/matrix to inform the data user that the results are suspect due to matrix
effects.

QUALITY CONTROL SAMPLES (QCS) — A QCS sample should be analyzed each
time that new Primary Dilution Standards (Sect. 7.2.3.2) are prepared. The source of
the QCS sample should ideally be a second vendor. Ifa second vendor is not
available then a different lot of the standard should be used. Although the use of pre-
methylated standards is prohibited for preparing analyte standard solutions, pre-
methylated standards may be used to prepare the QCS. The QCS may be injected as
a calibration standard or fortified into reagent water and analyzed as a LFB. If the
QCS is analyzed as a continuing calibration, then the acceptance criteria are the same
as for the CCC. If the QCS is analyzed as a LFB, then the acceptance criteria are the
same as for an LFB. If measured analyte concentrations are not of acceptable
accuracy, check the entire analytical procedure to locate and correct the problem
source.

515.4-20


TABLE 13: INITIAL DEMONSTRATION OF CAPABILITY (IDC) REQUIREMENTS

Method

replicate LFBs fortified at a
concentration estimated to

be near the Detection Limit.

Analyze the replicates
through all steps of the
analysis. Calculate the
Detection Limit using the
equation in Section 9.2.4.

Requirement Specification and Acceptance Criteria
Reference Frequency
Section Initial Analyze LRB prior to any Demonstrate that all target
9.2.1 Demonstration of | other IDC steps analytes are below '/, the
Low Method. reporting limit or lowest CAL
Background standard, and that possible
interference from extraction
media do not prevent the
identification and
quantification of method
analytes.
Section Initial Analyze 4-7 replicate LFBs_ | %RSD must be <20%
9.2.2 Demonstration of | fortified at midrange
Precision (IDP) concentration,
Section Initial Calculate average recovery | Mean recovery must be within
9.2.3 Demonstration of | for replicates used in IDP + 20% of true value.
Accuracy
Section Detection Limit Over a period of three days, | Must be < 1/3 of the
9.2.4 Determination prepare a minimum of 7 estab lished MRL.

Note: Data from Detection
Limit replicates are not
required to meet method
precision and accuracy criteria.
If the Detection Limit
replicates are fortified at a low
enough concentration, it is
likely that they will not meet
precision and accuracy criteria.

515.4-41



TABLE 9: LOW LEVEL PRECISION AND ACCURACY IN FORTIFIED CHLORINATED
GROUND WATER

Fortification Mean% % RSD

Compound Level (ug/L) Recovery (n=7)
Dalapon 1.0 105 1.5
3,5-Dichlorobenzoic acid 0.50 104 6.0
Dicamba 0.50 100 2.2
Dichlorprop 1.0 109 3.5
2,4-D 1.0 108 10
Pentachlorophenol 0.10 103 17
Silvex 0.25 96 3.0
2,4,5-T 0.25 91 3.4
2,4-DB 1.0 94 3.1
Chloramben 0.50 88 2.7
Dinoseb 1.0 100 40
Bentazon 1.0 101 2.8
Dacthal 0.50 62" 9.9
Quinclorac 0.10 107 5.7
Picloram 1.0 97 2.8
Acifluorfen 0.50 92 42
2,4-Dichlorophenylacetic acid (SUR) 25 95 3.1

“Dacthal was present in the chlorinated surface water at about 1/Sth the fortification
level. This was taken into account in the determination of the Mean % Recovery.

515.4-37


RAN 4

anne 4

4000 4

\ |
Nh oy

fae yt agp tp np a et a tt

FIGURE 2
CHROMATOGRAM OF THE CHLORPHENOXY HERBICIDES ON A DB-5 COLUMN
CHROMATOGRAPHIC CONDITIONS ARE GIVEN IN TABLE2.

us

Ww

14
I

| “ \ |

Fre a a

| 4 |
Ae apt pln st

Lips

|
call!

T
G &

10 te te nin

515.4-46


This primary dilution standard is used to fortify reagent water for
calibration standards. The lowest calibration standard concentration
must be at or below the MRL of each analyte. The concentrations of
the other standards should define a range containing the expected
sample concentrations or the working range of the detector.

7.24 CALIBRATION STANDARDS (CAL) - A five-point calibration curve is to
be prepared by fortifying reagent water with the primary dilution standard. A
designated amount of each calibration standard in acetone is spiked into
separate 40-mL aliquots of reagent water to produce acalibration curve
ranging from below or at the MRL to approximately 10-20 times the lowest
calibration level. These aqueous calibration standards should be treated like
samples and therefore require the addition of all preservation and other
reagents. They are extracted by the procedure described in Section 11. The
calibration standard solutions in acetone should be stored at < 0 °C.

8. SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1 SAMPLE BOTTLE PREPARATION

8.1.1 Grab samples must be collected in accordance with conventional sampling
practices” using amber glass containers with PTFE lined screw caps and
capacities of at least 40 mL.

8.1.2 Add sodium sulfite crystals (approximately 2 mg/40 mL of sample) to the
sample bottle prior to collecting the sample. This reagent eliminates residual
chlorine in the sample.

8.2. SAMPLE COLLECTION

8.2.1 Fill sample bottles but take care not to flush out the sodium sulfite. Because
the target analytes of this method are not volatile, it is not necessary to ensure
that the sample bottles are completely headspace free.

8.2.2. When sampling from a water tap, remove the aerator so that no air bubbles
will be trapped in the sample. Open the tap and allow the system to flush until
the water temperature has stabilized (usually about 3-5 minutes), Collect
samples from the flowing system.

8.2.3 When sampling from an open body of water, fill a 1 quart wide-mouth bottle

or | liter beaker with sample from a representative area, and carefully fill
sample vials from the container.

515.4-14


11.2

11.1.9

acids into the organic phase. The addition of salt also decreases the solubility
of MtBE in the aqueous phase and allows greater volumetric recovery. The
addition of this salt and the copper II sulfate pentahydrate should be done
quickly so that the heat generated from the addition of the acid (Section
11.1.6) will help dissolve the salts.

Add exactly 4.0-mL MtBE and shake vigorously for three minutes.

11.1.10 Allow the phases to separate for approximately 5 minutes.

SAMPLE METHYLATION WITH DIAZOMETHANE

11.2.1

11.2.2

11.2.3

11.2.4

GENERATION OF DIAZOMETHANE

11.2.1.1. Assemble the diazomethane generator (Figure 4) ina hood. The
collection vessel is a 10- or 15-mL, glass vial equipped with a
PTFE lined screw cap that is maintained at 0 - 5 °C.

11.2.1.2 Add a sufficient amount of MtBE (approximately 7 mL) to tube 1
to cover the first impinger. Add 10 mL of MtBE to the collection
vial. Set the nitrogen flow at 5-10 mL/min. Add 4-mL Diazald
solution (Sect. 7.1.13) and 3 mL of 37% KOH solution (Sect.
7.1.11) to the second impinger. Connect the tubing as shown and
allow the nitrogen flow to purge the diazomethane from the
reaction vessel into the collection vial for 30 minutes. Cap the vial
when collection is complete and maintain at 0-5 °C. When stored
at 0-5 °C, this diazomethane solution may be used over a period of
72 hours.

11.2.1.3. Several commercial sources of glassware are available for
diazomethane generation. These include a mini Diazald apparatus
from Aldrich (Cat. #:Z10,889-8).

Using a Pasteur pipette, transfer the sample extract (upper MtBE layer) to a 7-
mL, screw cap vial. Add 0.6 g acidified sodium sulfate (Sect. 7.1.8) and
shake. This step is included to dry the MtBE extract.

Using a Pasteur pipette, transfer the extract to a second, 7-mL glass vial.

Add 250 uL of the diazomethane solution prepared in Section 11.2.1 to each
vial. The contents of the vial should remain slightly yellow in color indicating
an excess of diazomethane. Additional diazomethane may be added if
necessary. Let the esterification reaction proceed for 30 minutes.

515.4-24


TABLE 14: QUALITY CONTROL REQUIREMENTS (SUMMARY)

Method

each analysis batch prior to
analyzing samples, after
every 10 samples, and after
the last sample.

Low CCC - near MRL

Mid CCC - near midpoint in
initial calibration curve
High CCC - near highest
calibration standard

Requirement Specification and Acceptance Criteria
Reference Frequency
e
Section Initial Calibration | Use internal standard When each calibration standard
10.2 calibration technique to is calculated as an unknown
generate a calibration curve. | using the calibration curve, the
Use at least 5 standard result must be 70-130% of the
concentrations. true value for all except the
lowest standard, which must be
50-150% of the true value.
Section Laboratory Daily, or with each Demonstrate that all target
9.4 Reagent Blank extraction batch of up to 20 _| analytes are below '/; the
(LRB) samples, whichever is more | method reporting limit or
frequent, lowest CAL standard, and that
possible interferences do not
prevent quantification of
method analytes.
If targets exceed '/, the MRL,
results for all subject analytes in
extraction batch are invalid.
Sections Continuing Verify initial calibration by | 1) The result for each analyte
9.5 and Calibration Check | analyzing a calibration must be 70-130% of the true
10.3 (CCC) standard at the beginning of | value for all but the lowest

standard. The lowest standard
must be 50-150% of the true
value.

2) The peak area of internal
standards must be 50-150% of
the average peak area calculated
during the initial calibration.
Results for analytes that do not
meet IS criteria or are not
bracketed by acceptable CCCs
are invalid.

515.4-42



3.9

3.10

3.11

3.12

3.13

3.14

3.15

3.16

3.17

second aliquot of the Field Sample used to prepare the LFM which is fortified,
extracted and analyzed identically. The LFMD is used instead of the Field Duplicate
to access method precision and accuracy when the occurrence of target analytes is
low.

LABORATORY DUPLICATES (LD1 and LD2) — Two aliquots of the same sample
taken in the laboratory and analyzed separately with identical procedures. Analyses of
LD1 and LD2 indicate precision associated with laboratory procedures, but not with
sample collection, preservation, and storage procedures,

FIELD DUPLICATES (FD1 and FD2) —Two separate samples collected at the same
time and place under identical circumstances, and treated exactly the same throughout
field and laboratory procedures. Analyses of FD1 and FD2 give a measure of the
precision associated with sample collection, preservation, and storage, as well as with
laboratory procedures.

STOCK STANDARD SOLUTION (SSS) - A concentrated solution containing one
or more method analytes prepared in the laboratory using assayed reference materials
or purchased from a reputable commercial source.

PRIMARY DILUTION STANDARD SOLUTION (PDS) - A solution containing
method analytes prepared in the laboratory from stock standard solutions and diluted
as needed to prepare calibration solutions and other needed analyte solutions.

CALIBRATION STANDARD (CAL) — A solution prepared from the primary
dilution standard solution or stock standard solutions and the internal standards and
surrogate analytes. The CAL solutions are used to calibrate the instrument response
with respect to analyte concentration.

CONTINUING CALIBRATION CHECK (CCC) - A calibration standard containing
one or more method analytes, which is analyzed periodically to verify the accuracy of
the existing calibration for those analytes.

QUALITY CONTROL SAMPLE (QCS) - A solution of method analytes of known
concentrations that is obtained from a source external to the laboratory and different
from the source of calibration standards. It is used to check standard integrity.

DETECTION LIMIT — The minimum concentration of an analyte that can be
identified, measured and reported with 99% confidence that the analyte concentration
is greater than zero (Section 9.2.4). This is a statistical determination of precision.
Accurate quantitation is not expected at this level.”

MINIMUM REPORTING LEVEL (MRL) — The minimum concentration that can be

515.4-5


TABLE 7: LOW LEVEL PRECISION AND ACCURACY IN FORTIFIED CHLORINATED
SURFACE WATER

Fortification Mean% % RSD

Compound Level (ug/L) Recovery (n=7)
Dalapon 1.0 104 21
3,5-Dichlorobenzoic acid 0.50 110 3.0
Dicamba 0.50 93 44
Dichlorprop 1.0 93 11
2,4-D 1.0 97 5.2
Pentachlorophenol 0.10 86 3.2
Silvex 0.25 103 43
2,4,5-T 0.25 100 3.5
2,4-DB 1.0 104 5.9
Chloramben 0.50 93 2.0
Dinoseb 1.0 99 1.2
Bentazon 1.0 91 2.2
Dacthal 0.50 92 46
Quinclorac 0.10 96 15
Picloram 1.0 102 2.4
Acifluorfen 0.50 98 4.1
2,4-Dichlorophenylacetic acid (SUR) 25 107 1.5

515.4-35


10.

CALIBRATION AND STANDARDIZATION

10.1

10.2

After initial calibration is successful, a Continuing Calibration Check (CCC) is
required at the beginning and end of each analysis batch, and after every tenth sample
(Sect. 10.3). Because this is a procedural standard method, the analyst will need to
make a decision to include an appropriate number of CCCs or an entire initial
calibration curve with each extraction batch. Initial calibration should be repeated
each time a major instrument modification or maintenance is performed.

INITIAL CALIBRATION

10.2.1

10.2.2

10.2.3

10.2.4

Establish GC operating parameters equivalent to the suggested specifications
in Section 17, Table 1. The GC system must be calibrated using the internal
standard (IS) technique. Other columns or conditions may be used if
equivalent or better performance can be demonstrated.

Prepare a set of at least 5 calibration standards as described in Section 7.2.4.
The lowest concentration of calibration standard must be at or below the
MRL, which will depend on system sensitivity.

CALIBRATION - Use the GC data system software to generate a linear
regression or quadratic calibration curve using the internal standard. The
analyst may choose whether or not to force zero to obtain a curve that best fits
the data. Examples of common GC system calibration curve options are:

1) A, /A,, vs Q, /Q, and 2) RRF vs A, /A,,.

where:

P

integrated peak area of the analyte,
= integrated peak area of the internal standard,
= quantity of analyte injected in ng or concentration units,
and
= quantity of internal standard injected in ng or concentration
units.

oO p>
I

As an alternative, concentrations may be calculated through the use of average
relative response factor (RRF). Calculate the RRFs using the equation

AQ
(AYO)

Average RRF calibrations may only be used if the RRF values over the

$15.4-21


sample volume and any dilutions performed.

12.5 Analyte concentrations are reported in ug/L as the total free acid. Calculations should
use all available digits of precision.
13. METHOD PERFORMANCE
13.1 PRECISION, ACCURACY, AND Detection Limits — Tables for these data are
presented in Section 17. Single laboratory precision and accuracy data are presented
in Tables 5 -10. Detection Limits are presented in Table 4 and were calculated using
the formula presented in Section 9.2.4.
14. POLLUTION PREVENTION
14.1 This method utilizes liquid:liquid microextraction to extract analytes from water. It
requires the use of very small volumes of organic solvent and very small quantities of
pure analytes, thereby minimizing the potential hazards to both the analyst and the
environment as compared to the use of large volumes of organic solvents in
conventional liquid-liquid extractions.
14.2 For information about pollution prevention that may be applicable to laboratory
operations, consult “Less is Better: Laboratory Chemical Management for Waste
Reduction” available from the American Chemical Society’s Department of
Government Relations and Science Policy, 1155 16th Street N.W., Washington, D.C.,
20036.
15. WASTE MANAGEMENT
15.1 The analytical procedures described in this method generate relatively small amounts

of waste since only small amounts of reagents and solvents are used. The matrices of
concern are finished drinking water or source water. However, the Agency requires
that laboratory waste management practices be conducted consistent with all
applicable rules and regulations, and that laboratories protect the air, water, and land
by minimizing and controlling all releases from fume hoods and bench operations.
Also, compliance is required with any sewage discharge permits and regulations,
particularly the hazardous waste identification rules and land disposal restrictions.
For further information on waste management, consult “The Waste Management
Manual for Laboratory Personnel” also available from the American Chemical
Society at the address in Section 14.2.

515.4-27


11.

PROCEDURE

11.1

SAMPLE EXTRACTION AND HYDROLYSIS

1.1.1

11.1.2

11.1.3

11.1.4

11.1.5

11.1.6

11.1.7

11.1.8

Remove the samples from storage (Sect. 8.3) and allow them to equilibrate to
room temperature.

Place 40 mL of the water sample into a precleaned 60-mL, glass vial with a
PTFE lined screw cap using a graduated cylinder.

Add 10 uL of surrogate standard (100 ug/mL, 2,4-dichlorophenylacetic acid in
acetone per Section 7.2.2) to the aqueous sample.

Add 1 mL, of the 4 N NaOH solution prepared in Section 7.1.10 to each glass
vial. Check the pH of the sample with pH paper or a pH meter. If the sample
does not have a pH greater than or equal to 12, adjust the pH by adding more
4N NaOH solution. Let the sample sit at room temperature for 1 hour,
shaking the contents periodically.

NOTE: Since many of the herbicides contained in this method are applied as a
variety of esters and salts, it is vital to hydrolyze them to the parent acid prior
to extraction. This step must be included in the analysis of all extracted field
samples, LRBs, LFMs and calibration standards. Failure to perform this step
may result in data that are biased low for some targets in field samples.

Following hydrolysis, add 5 mL of (90:10, v:v) hexane:MtBE (Section 7.1.5)
and shake vigorously for three minutes. Allow the phases to separate for
approximately 5 minutes then remove and discard the top hexane/MtBE layer.
This wash aids in sample cleanup and removes any Dacthal from the sample
which would interfere with the quantitation of the Dacthal metabolites.

Adjust the pH to approximately 1 by adding concentrated sulfuric acid. Cap,
shake and then check the pH with a pH meter or narrow range pH paper. Add
additional sulfuric acid as needed to properly adjust the pH.

Quickly add approximately 2 g of copper II sulfate pentahydrate and shake
until dissolved. This colors the aqueous phase blue and allows the analyst to
better distinguish between the aqueous phase and the organic phase in this
micro extraction.

Quickly add approximately 16 g of muffled sodium sulfate (Sect. 7.1.7) and

shake until almost all is dissolved. Sodium sulfate is added to increase the
ionic strength of the aqueous phase and thus further drive the chlorophenoxy

515,.4-23


TABLE 8: MID LEVEL PRECISION AND ACCURACY IN FORTIFIED CHLORINATED
SURFACE WATER

Fortification Mean%  % RSD

Compound Level (ug/L) Recovery (n=7)
Dalapon 10 100 2.5
3,5-Dichlorobenzoic acid 5.0 104 2.6
Dicamba 5.0 102 29
Dichlorprop 10 101 1.2
2,4-D 10 101 1.2
Pentachlorophenol 1.0 100 1.0
Silvex 2.5 101 1.0
2,4,5-T 2.5 100 1.6
2,4-DB 10 101 2.3
Chloramben 5.0 102 2.6
Dinoseb 10 101 1.6
Bentazon 10 98 1.8
Dacthal 5.0 99 2.0
Quinclorac 1.0 105 2.5
Picloram 10 107 3.2
Acifluorfen 5.0 92 24
2,4-Dichlorophenylacetic acid (SUR) 25 106 1.4

515.4-36


9.8

9.9

9.7.1 If the reinjected aliquot produces an acceptable internal standard response,
report results for that aliquot.

9.7.2 Ifthe internal standard area for the reinjected extract deviates greater than
50% from the initial calibration average, the analyst should check the
continuing calibration check standards that ran before and after the sample. If
the continuing calibration check fails the criteria of Section 10.3, recalibration
is in order per Section 10. If the calibration standard is acceptable, extraction
of the sample should be repeated provided the sample is still within holding
time. Otherwise, report results obtained from the reinjected extract, but
annotate as suspect.

SURROGATE RECOVERY -— The surrogate standard is fortified into the aqueous
portion of all samples, LRBs, and LFMs and LFMDs prior to extraction. It is also
added to the calibration curve and calibration check standards. The surrogate is a

means of assessing method performance from extraction to final chromatographic

measurement.

9.8.1 When surrogate recovery from a sample, blank, or CCC is less than 70% or
greater than 130%, check (1) calculations to locate possible errors, (2)
standard solutions for degradation, (3) contamination, and (4) instrument
performance. Ifthose steps do not reveal the cause of the problem, reanalyze
the extract.

9.8.2 Ifthe extract reanalysis meets the surrogate recovery criterion, report only data
for the reanalyzed extract.

9.8.3 If the extract reanalysis fails the 70-130% recovery criterion, the analyst
should check the calibration by injecting the last calibration standard that
passed. If the calibration standard fails the criteria of Section 9.8.1,
recalibration is in order per Section 10.2. If the calibration standard is
acceptable, extraction of the sample should be repeated provided the sample is
still within the holding time. If the sample re-extract also fails the recovery
criterion, report all data for that sample as suspect/surrogate recovery to
inform the data user that the results are suspect due to surrogate recovery.

LABORATORY FORTIFIED SAMPLE MATRIX AND DUPLICATE (LFM AND
LFMD) - Analyses of LFMs (Sect. 3.7) are required in each extraction batch and are
used to determine that the sample matrix does not adversely affect method accuracy.
If the occurrence of target analytes in the samples is infrequent, or if historical trends
are unavailable, a second LFM or LMFD must be prepared, extracted, and analyzed
from a duplicate field sample used to prepare the LFM to assess method precision.
Extraction batches that contain LFMDs will not require the analysis of a Field

515.4-18


7.2

717

7110

TAAL

7.112

7.113

7AA4

TAS

7.1.16

TAAT

SODIUM SULFATE, Na2S04 -— Pesticide grade, granular, anhydrous.
Interferences have been observed when lower quality grades have been used.
If interferences are observed, it may be necessary to heat the sodium sulfate in
a shallow tray at 400 °C for up to 4 hr to remove phthalates and other
interfering organic substances. Alternatively, it can be extracted with
methylene chloride in a Soxhlet apparatus for 48 hr. Store in a capped glass
bottle rather than a plastic container.

ACIDIFIED SODIUM SULFATE - Acidify by slurrying 100 g of muffled
sodium sulfate with enough ethyl ether to just cover the solid. Add 0.5-mL
concentrated sulfuric acid dropwise while mixing thoroughly. Remove the
ether under vacuum. Mix | g of the resulting solid with 5-mL of reagent
water and measure the pH of the mixture. The pH must be below pH 4. Store
ina desiccator or at 100°C to keep the reagent dry.

COPPER II SULFATE PENTAHYDRATE, CUS0,-5H,0 — ACS reagent
grade or better.

4N SODIUM HYDROXIDE SOLUTION - Dissolve 16 g sodium hydroxide
(NaOH) pellets (ACS grade or equivalent) in reagent water and dilute to 100
mL.

POTASSIUM HYDROXIDE SOLUTION (37%, w/v) — Dissolve 37 g of
potassium hydroxide (KOH) pellets (ACS grade or equivalent) in reagent
water and dilute to 100 mL.

SODIUM SULFITE, Na,S0, — ACS reagent grade, used as a dechlorinating
agent in this method.

DIAZALD SOLUTION - Prepare a solution containing 5 g diazald (ACS
reagent grade) in 50 mL of a 50:50 (v/v) mixture of MtBE and carbitol. This
solution is stable for one month or longer when stored at 4 °C in an amber
bottle with a PTFE lined screw cap.

SULFURIC ACID — Concentrated, ACS reagent grade.

SILICA GEL - ACS reagent grade, 35-60 mesh.

HYDROGEN - 99.999% pure or better, GC carrier gas.

NITROGEN - 99.999% pure or better, ECD make-up gas.

STANDARD SOLUTIONS - When a compound purity is assayed to be 96% or

515.4-10


TABLE 5: LOW LEVEL PRECISION AND ACCURACY IN REAGENT WATER

Compound Fortification Mean% % RSD SIN
Level (ug/L) Recovery (n=7)  Ratio*

Dalapon 1.0 108 2.2 578
3,5-Dichlorobenzoic acid 0.50 117 16 9
Dicamba 0.50 97 3.7 35
Dichlorprop 1.0 95 5.7 19
2,4-D 1.0 98 5.2 23
Pentachlorophenol 0.10 76 74 21
Silvex 0.25 84 20 9
2,4,5-T 0.25 96 73 16
2,4-DB 1.0 97 8.4 6
Chloramben 0.50 90 9.0 113
Dinoseb 1.0 103 6.7 8
Bentazon 1.0 100 2.1 41
Dacthal 0.50 92 6.5 100
Quinclorac 0.10 106 9.3 20
Picloram 1.0 92 2.6 23
Acifluorfen 0.50 77 5.9 80
2,4-Dichlorophenylacetic acid (SUR) 25 104 8.0 -

“Signal-to-noise ratios were calculated for each target compound peak by dividing the
peak height for each compound by the peak-to-peak noise, which was determined for
each component from the method blank over a period of time equal to the full peak

width in the target analyte’s retention time window.

515.4-33



TABLE 2: CHROMATOGRAPHIC CONDITIONS AND AVERAGE RETENTION TIME
DATA FOR THE CONFIRMATION COLUMN (DB-5, 40 m x 180 um i.d.)

Peak Number Average T,

(Figure 1) Compound (min)* % RSD
1 Dalapon 5.04 0.057
2 3,5-Dichlorobenzoic acid 10.33 0.007
3 2,4-Dichlorophenylacetic acid (SUR) 11.31 0.004
4 Dicamba 11.46 0.006
5 Dichlorprop 12.19 0.006
6 4,4'-Dibromooctafluorobiphenyl (IS) 12.71 0.004
7 2,4-D 12.34 0.005
8 Pentachlorophenol 13.16 0.006
9 Silvex 13.29 0.004
10 2,4,5-T 13.48 0.005
11 2,4-DB 13.94 0.005
12 Chloramben 13.34 0.004
13 Dinoseb 14.01 0.004
14 Bentazon 14.28 0.006
15 Dacthal 15.00 0.004
16 Quinclorac 14.88 0.004
17 Picloram 14.59 0.004
18 Acifluorfen 16.38 0.003

* The average retention time represents the average of 7 runs.

Confirmation Column:
DB-5, 40 m x 0.180 mm id., 0.20 ym film thickness, injector temp. 200 °C, liner 2 mm straight siltek®
deactivated, injection volume 1 1L of 100 ng/mL (highest level component) standard, splitless injection hold to
1 min then purge @ 50 mL/min, detector temp 360 °C, detector make up gas nitrogen at 20 mL/minute.
Temperature program: 45 °C initial, program at 4 “C/minute to 80°C then program at 30 ‘C/minute to 280 and
Hold for 2 min, Data collection via HP GC Chemstation at a rate of 20Hz.

Carrier gas; Hydrogen (UHP)

Detector makeup gas: Nitrogen (UHP)

515.4-30


5.

44

4.3.1 During method development a contaminant was found in local ground water
and surface water that interfered with the analysis of Dalapon on the primary
column. Due to this interferent, it was necessary to carefully optimize the
chromatographic conditions (see Table 1). A slow initial temperature program
was needed to ensure separation of the interferent from Dalapon. Analyte
identifications should be confirmed using the confirmation column specified
in Table 2 or another column that is dissimilar to the primary column or by
GC/MS if the concentrations are sufficient.

Interferences by phthalate esters can pose a major problem in pesticide analysis when
using an electron capture detector (ECD). These compounds generally appear in the
chromatogram as large peaks. Common flexible plastics contain varying amounts of
phthalates that are easily extracted or leached during laboratory operations. Cross
contamination of clean glassware routinely occurs when plastics are handled during
extraction steps, especially when solvent-wetted surfaces are handled. Interferences
from phthalates can best be minimized by avoiding the use of plastics in the
laboratory. Exhaustive purification of reagents and glassware may be required to
eliminate background phthalate contamination.”»

SAFETY

5.1

5.2

5.3

5.4

The toxicity or carcinogenicity of each reagent used in this method has not been
precisely defined. Each chemical compound should be treated as a potential health
hazard, and exposure to these chemicals should be minimized. The laboratory is
responsible for maintaining a current awareness file of OSHA regulations regarding
the safe handling of the chemicals specified in this method. A reference file of
MSDSs should also be made available to all personnel involved in the chemical
analysis. Additional references to laboratory safety are available.“

Pure standard materials and stock standards of these compounds should be handled
with suitable protection to skin and eyes, and care should be taken not to breathe the
vapors or ingest the materials.

The toxicity of the extraction solvent, MTBE, has not been well defined. Susceptible
individuals may experience adverse affects upon skin contact or inhalation of vapors.
Therefore protective clothing and gloves should be used and MTBE should be used
only in a chemical fume hood or glove box. The same precaution applies to pure
standard materials.

Diazomethane is a toxic carcinogen which can explode under certain conditions. The
following precautions must be followed.

5.4.1 Use the diazomethane generator behind a safety shield in a well ventilated

515.4-7


3.19

reported as a quantified value for a target analyte in a sample following analysis. This
defined concentration can be no lower than the concentration of the lowest continuing
calibration standard for that analyte, and can only be used if acceptable quality control
criteria for this standard are met.

PROCEDURAL STANDARD CALIBRATION - A calibration method where
aqueous calibration standards are prepared and processed (e.g., purged, extracted,
and/or derivatized) in exactly the same manner as a sample. All steps in the process
from addition of sampling preservatives through instrumental analyses are included in
the calibration. Using procedural standard calibration compensates for any
inefficiencies in the processing procedure.

MATERIAL SAFETY DATA SHEET (MSDS) — Written information provided by
vendors concerning a chemical’s toxicity, health hazards, physical properties, fire, and
reactivity data including storage, spill, and handling precautions.

INTERFERENCES

4.1

4.2

43

All glassware must be meticulously cleaned. Wash glassware with detergent and tap
water, rinse with tap water, followed by reagent water. A final rinse with solvents
may be needed. In place ofa solvent rinse, non-volumetric glassware can be muffled
at 400 °C for 2 hours. Volumetric glassware should not be heated in an oven above
120°C. Store inverted or capped with aluminum foil.

Method interferences may be caused by contaminants in solvents, reagents (including
reagent water), sample bottles and caps, and other sample processing hardware that
lead to discrete artifacts and/or elevated baselines in the chromatograms. All items
such as these must be routinely demonstrated to be free from interferences (less than
'/, the MRL for each target) under the conditions of the analysis by analyzing
laboratory reagent blanks as described in Section 9. Subtracting blank values from
sample results is not permitted.

4.2.1 During method development it was found that sodium sulfate from several
sources contained multiple interferences. After screening several brands, it
was found that a grade suitable for pesticide residue analysis provided the best
results. If the suitability of the available sodium sulfate is in question, extract
and analyze a laboratory reagent blank (section 3.5) to test for interferences
prior to sample processing.

Matrix interferences may be caused by contaminants that are extracted from the

sample. The extent of matrix interferences will vary considerably from source to
source, depending upon the water sampled.

515.4-6


Duplicate (Sect. 9.10). Ifa variety of different sample matrices are analyzed
regularly, for example, drinking water from groundwater and surface water sources,
method performance should be established for each. Over time, LFM data should be
documented for all routine sample sources for the laboratory.

9.9.1 Within each extraction batch, a minimum of one field sample is fortified as an
LEM for every 20 samples extracted. The LFM is prepared by spiking a
sample with an appropriate amount of Analyte PDS (Sect. 7.2.3.2). Select a
spiking concentration that is at least twice the matrix background
concentration, if known. Use historical data and rotate through the designated
concentrations when selecting a fortifying concentration.

9.9.2 Calculate the percent recovery (R) for each analyte using the equation

ne AcB

*100

where

A= measured concentration in the fortified sample,

B = measured concentration in the unfortified sample, and
C = fortification concentration.

9.9.3. Analyte recoveries may exhibit matrix bias. For samples fortified at or above
their native concentration, recoveries should range between 70 and 130%,
except for low-level fortification near or at the MRL where 50 to 150%
recoveries are acceptable. If the accuracy of any analyte falls outside the
designated range, and the laboratory performance for that analyte is shown to
be in control in the LFB, the recovery is judged to be matrix biased. The
result for that analyte in the unfortified sample is labeled suspect/matrix to
inform the data user that the results are suspect due to matrix effects.

9.9.4 Ifan LFMD is analyzed instead of a Field Duplicate (Sect. 9.10), calculate the
relative percent difference (RPD) for duplicate LFMs (LFM and LFMD) using
the equation

LFM- LFMD

= ———_—______ + 100
(LFM+ LFMD)/2

RPDs for duplicate LFMs should fall in the range of + 30% for samples
fortified at or above their native concentration. Greater variability may be
observed when LFMs are spiked near the MRL. At the MRL, RPDs should
fall in the range of + 50% for samples fortified at or above their native

515.4-19


equivalent), if the fast GC option is used the modifications should include a high
pressure (= 50 psi) split/splitless injector, fast temperature ramp oven (50 °C/minute)
and a low volume (150 tL ) micro ECD detector. Additionally, adata system capable
of fast sampling (20 points/peak) is required.

6.13 PRIMARY GC COLUMN - RTX-1701, 180 um i.d., fused silica capillary with
chemically bonded (14% cyanopropylphenyl-methylpolysiloxane), or equivalent
bonded, fused silica column.

6.14 CONFIRMATION GC COLUMN - DB-S, 180 um i.d., fused silica capillary with
chemically bonded (5% phenyl-methylpolysiloxane), or equivalent bonded, fused
silica column.

REAGENTS AND STANDARDS

7A REAGENTS AND SOLVENTS - Reagent grade or better chemicals should be used

in all analyses. Unless otherwise indicated, itis intended that all reagents shall
conform to the specifications of the Committee on Analytical Reagents of the
American Chemical Society, where such specifications are available. Other grades
may be used, provided it is first determined that the reagent is of sufficiently high
purity to permit its use without lessening the quality of the determination.

7.1.1 REAGENT WATER - Purified water which does not contain any measurable
quantities of any target analytes or interfering compounds greater than 1/3 the
MRL for each compound of interest.

7.1.2 METHYL tert-BUTYL ETHER (MtBE) — High purity, demonstrated to be
free from analytes and interferences (HPLC grade or better).

7.1.3 ACETONE - High purity, demonstrated to be free from analytes and
interferences (HPLC grade or better).

7.1.4 CARBITOL (DIETHYLENE GLYCOL MONOETHYL ETHER) - High
purity, demonstrated to be free from analytes and interferences (HPLC grade
or better).

7.1.5 HEXANE:MtBE (90:10, v/v) WASH SOLVENT - High purity, unpreserved,
demonstrated to be free from analytes and interferences (HPLC grade or
better).

7.1.6 HEXANE - High purity, demonstrated to be free from analytes and
interferences (HPLC grade or better).

515.4-9


11.2.5 Remove any unreacted diazomethane by adding 0.1 g of silica gel.
Effervescence (evolution of nitrogen) is an indication that excess
diazomethane was present. Allow the extracts to sit for 0.5 hour.

11.2.6 Transfer the extract to an autosampler vial. A duplicate vial may be filled
using the excess extract.

11.2.7 Analyze the sample extracts as soon as possible. The sample extract may be
stored up to 21 days if kept at 0 °C or less. Keep the extracts away from light
in amber glass vials with PTFE lined caps.

11.3. GAS CHROMATOGRAPHY

11.3.1 Ifthe fast GC option is used, several important changes from “conventional
GC” should be made to aid in the rapid analysis of the analytes. The
instrument should have a fast temperature ramp (50 °C/minute) oven and a
high pressure (= 50 psi) split/splitless injector. When using columns with
diameters less than 180 um the instrument should be equipped with a low
volume (150 L ) micro ECD. Additionally, the column diameter and film
thickness should be decreased and the carrier gas should be changed to
hydrogen.

11.3.2 Use of Hydrogen Safely — Although hydrogen can be used safely as a carrier
gas, the potential for fire or explosion does exist if the gas system is
mishandled. If youare unsure of the safety guidelines for using hydrogen as a
carrier gas, seek advice from your instrument manufacturer regarding its use.

11.3.3 Column Selection and. Installation —- During method development the RTX-
1701 columns provided baseline resolution for the 2,4-DB /Chloramben pair
(peaks 11 and 12 in Figure 1). Columns from other manufacturers were not as
effective in separating these analytes. Strict attention must be paid to
established column installation guidelines with regard to the proper cutting
and placement of the capillary columns within the instrument. Additionally, a
loss of response over time was noted for Acifluorifen and Dinoseb. Trimming
approximately 1 meter from the head of the column restored the response for
these analytes. If conditions in the laboratory necessitate frequent column
trimming, a guard column is recommended.

11.4 ANALYSIS OF EXTRACTS
11.4.1 Establish operating conditions as described in Section 17, Table 1 (Table 2 if

performing confirmation). Confirm that retention times, compound separation
and resolution are similar to those summarized in Table | and Figurel.

515.4-25


METHOD 515.4 DETERMINATION OF CHLORINATED ACIDS IN DRINKING
WATER BY LIQUID-LIQUID MICROEXTRACTION,
DERIVATIZATION, AND FAST GAS CHROMATOGRAPHY WITH
ELECTRON CAPTURE DETECTION

Revision 1.0
April 2000
S.C. Wendelken, M.V. Bassett, T.A. Dattilio, and B.V. Pepich (IT Corporation)
D.J. Munch (US EPA, Office of Ground Water and Drinking Water) - Method 515.4, Revision 1.0

(2000)

A. M. Pawlecki-Vonderheide (ICI) and D.J. Munch (US EPA, Office of Ground Water and Drinking
Water) - Method 515.3, Revision 1.0 (1996)

J.W. Hodgeson - Method 515.2, Revision 1.0 (1992)
R.L. Graves - Method 515.1, Revision 4.0 (1989)

T. Engels (Batelle Columbus Laboratory) and D.J. Munch (US EPA, Office of Ground Water and
Drinking Water) - National Pesticide Survey Method 3, Revision 3.0 (1987)

J.W. Hodgeson - Method 515, Revision 2.0 (1986)

TECHNICAL SUPPORT CENTER
OFFICE OF GROUND WATER AND DRINKING WATER
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268

$15.4-1


FIGURE 4

DIAZOMETHANE GENERATOR

Nitrogen
——_
—,
(| =
Le
: (|
MtBE —> ae — MBE in collection
vial
eid «— = lcebath
Diazald+KOH —> | F
Naat

515.4-48


9 are met.

7.2.2.1 SURROGATE STOCK SOLUTION (1.0 mg/mL) — Prepare a
surrogate stock standard solution of 2,4-dichlorophenylacetic acid by
weighing 0.0100 g of neat material. Dissolve the neat material in
acetone and dilute to volume in a 10-mL volumetric flask. Transfer the
solution to an amber glass vial with a PTFE lined screw cap and store
at < 0°C. The resulting concentration of the stock surrogate solution
will be 1.0 mg/mL.

7.2.2.2 SURROGATE PRIMARY DILUTION STANDARD/SUR SAMPLE
FORTIFICATION SOLUTION (100 ug/mL) — Prepare a primary
dilution standard at approximately 100 ug/mL by the addition of 1 mL
of the stock standard to 10 mL of acetone. Transfer the primary
dilution to an amber glass vial with a PTFE lined screw cap and store
at < 0°C. Addition of 10 ul, of the primary dilution standard to the
40-mL aqueous sample results in a surrogate concentration of 25
ng/mL. The solution should be replaced when ongoing QC indicates a
problem.

7.2.3 ANALYTE STANDARD SOLUTIONS - Obtain the analytes listed in the
table in Section 1.1 as neat or solid free acid standards or as commercially
prepared ampulized solutions from a reputable standard manufacturer. The
use of pre-methylated standards is not allowed for the preparation of analyte
standards. Prepare the Analyte Stock and Primary Dilutions Standards as
described below.

7.2.3.1 ANALYTE STOCK STANDARD SOLUTION - Prepare separate
stock standard solutions for each analyte of interest at a concentration
of 1-5 mg/mL in acetone. Method analytes may be obtained as neat
materials or ampulized solutions (> 99% purity) from a number of
commercial suppliers. These stock standard solutions should be stored
at< 0°C,

7.2.3.1.1 For analytes which are solids in their pure form, prepare
stock standard solutions by accurately weighing
approximately 0.01 to 0.05 grams of pure material in a 10-
mL volumetric flask. Dilute to volume with acetone.

7.2.3.1.2 For analytes which are liquid in their pure form at room
temperature, place about 9.8 mL of acetone into a 10-mL
volumetric flask. Allow the flask to stand, unstoppered, for
about 10 minutes to allow solvent film to evaporate from

515.4-12


greater, the weight can be used without correction to calculate the concentration of the
stock standard. Solution concentrations listed in this section were used to develop
this method and are included as an example. Standards for sample fortification
generally should be prepared in the smallest volume that can be accurately measured
to minimize the addition of organic solvent to aqueous samples. Laboratories
should use standard QC procedures to determine when Standard Solutions
described in this section need to be replaced.

721

INTERNAL STANDARD SOLUTIONS -— 4,4-Dibromooctafluorobiphenyl,
99+% is used as an internal standard for the method. This compound has been
shown to be an effective internal standard for the method analytes, but other
compounds may be used if the QC requirements in Section 9 are met.

7.2.1.1 INTERNAL STANDARD STOCK SOLUTION (2.0 mg/mL) —

Prepare an internal standard a stock solution by accurately weighing
approximately 0.0200 g of neat 4,4'- dibromooctafluorobiphenyl
material. Dissolve the neat material in MtBE and dilute to volume in a
10-mL volumetric flask. Transfer the solution to an amber glass vial
with a PTFE-lined screw cap and store at < 0 °C. The resulting
concentration of the stock internal standard solution will be
approximately 2.0 mg/mL.

7.2.1.2 INTERNAL STANDARD PRIMARY DILUTION STANDARD (2.5

ug/mL) — Prepare a internal standard fortification solution at
approximately 2.5 ug/mL by the addition of 12.5 uL of the stock
standard to 10 mL of MtBE. Transfer the primary dilution to an amber
glass vial with a PTFE lined screw cap and store at < 0 °C. The
solution should be replaced when ongoing QC indicates a problem.

7.2.1.3 MtBE EXTRACTION SOLVENT WITH INTERNALSTANDARD

(2.5 ug/mL) - The internal standard 4,4'-dibromooctafluorobiphenyl is
added to the extraction solvent prior to analyte extraction to
compensate for any volumetric differences encountered during sample
processing. This solution should be made fresh prior to extraction.
The addition of 1 mL of the primary dilution standard (2.5 ug/mL) to
99-mL MBE results in a final internal standard concentration of 25
ng/mL. This solution is used to extract the samples (Sect. 11.1).

7.2.2 SURROGATE (SUR) ANALYTE STANDARD SOLUTION —

2,4-Dichlorophenylacetic acid (99+%) is used as a surrogate compound in this
method to evaluate the extraction and derivatization procedures. This
compound has been shown to be an effective surrogate for the method
analytes, but other compounds may be used if the QC requirements in Section

$15.4-11


Method

Requirement Specification and Acceptance Criteria
Reference Frequency
Section 8.4 | Sample 14 days with appropriate | Sample results are valid only if
Holding Time | preservation and storage samples are extracted within sample
hold time.
Section 8.4 | Extract 21 days with appropriate | Sample results are valid only if
Holding Time | storage extracts are analyzed within extract

hold time.

515.4-44



TABLE 4: DETECTION LIMITS IN REAGENT WATER

Primary Secondary
Fortification Column Column
Compound Level (ug/L) Letection Detection
imit* (ug/L) Limit* (ug/L)
Dalapon 0.100 0.054 0.074
3,5-Dichlorobenzoic acid 0.050 0.212 0.049
Dicamba 0.050 0.032 0.042
Dichlorprop 0.100 0.433 0.12
2,4-D 0.100 0.055 0.066
Pentachlorophenol 0.010 0.014 0.084
Silvex 0.025 0.033 0.018
2,4,5-T 0.025 0.024 0.033
2,4-DB 0.100 0.246 0.182
Chloramben 0.050 0.057 0.083
Dinoseb 0.100 0.166 0.081
Bentazon 0.100 0.064 0.185
Dacthal 0.050 0.113 0.105
Quinclorac 0.050 0.080 0.113
Picloram 0.050 0.076 0.055
Acifluorfen 0.250 0.307 0.092

*Detection Limits were extracted and analyzed over 3 days for 9 replicates following
the procedure outlined in Section 9.

515.4-32


TABLE 3: CHROMATOGRAPHIC CONDITIONS AND AVERAGE RETENTION TIME
DATA FOR A CONVENTIONAL PRIMARY COLUMN (DB-5, 30 m x 250 um i.d.)

Peak Number T,
(Figure 3) Compound (min)
1 Dalapon 14.28
2 3,5-Dichlorobenzoic acid 20.35
3 2,4-Dichlorophenylacetic acid (SUR) 20.98
4 Dicamba 21.10
5 Dichlorprop 21.46
6 4,4'-Dibromooctafluorobiphenyl (IS) 21.53
7 2,4-D 21.64
8 Pentachlorophenol 21.81
9 Silvex 22.03
10 2,4,5-T 22.27
11 2,4-DB 22.51
12 Chloramben 22.55
13 Dinoseb 22.94
14 Bentazon 23.17
15 Dacthal 23.30
16 Quinclorac 23.55
17 Picloram 23.82
18 Acifluorfen 25.90

Conventional Primary Column:
DB-1701, 30 m x 0.250 mm id., 0.25 ym film thickness, injector temp. 200 °C, liner2 mm straight deactivated,
injection volume 1 LL of 100 ng/mL (highest level component) standard, splitless injection hold to .5 min then
purge @ 30 mL/min, detector temp 290 'C, detector make up gas P-5 at 60 mL/ninute. Temperature program:
45°C initial, hold 10 min then program at 5 ‘C/minute to 70°C, Then 30 ‘C/minute to 260°C, and Hold for 5
min, Data collection via Turbochrom 4.1

Carrier gas; Helium (UHP)

Detector makeup gas: 5% methane/argon (UHP)

515.4-31


5.5

fume hood. Under no circumstances can the generator be heated above 90°C,
and all grinding surfaces such as ground glass joints, sleeve bearings and glass
stirrers must be avoided. To minimize safety hazards, the diazomethane
generator apparatus used in the esterification procedure (Sect 11.2) produces
micro molar amounts of diazomethane in solution. If the procedure is
followed carefully, no possibility for explosion exists.

Although hydrogen can be safely used as a carrier gas, the potential for fire or
explosion does exist if the gas system is mishandled. If you are unsure of the safety
guidelines for using hydrogen as a carrier gas, seek advice from your instrument
manufacturer regarding its use.

APPARATUS AND EQUIPMENT

6.1

6.2

6.3

6.4

6.5

6.6

6.7

6.8

6.9

6.10

6.11

6.12

SAMPLE CONTAINERS - Amber glass bottles, approximately 40 mL, fitted with
PTFE (polytetrafluoroethylene) lined screw caps.

EXTRACTION VIALS - 60-mL clear glass vials with PTFE lined screw caps.

AUTOSAMPLER VIALS — 2.0-mL vials with screw or crimp cap and a PTFE faced
seal.

STANDARD SOLUTION STORAGE CONTAINERS -— 10 to 20-mL amber glass
vials with PTFE lined screw caps.

CLEAR VIALS - 7-mL glass, disposable, with PTFE lined screw caps for extract
drying and derivatization.

PASTEUR PIPETTES -— Glass, disposable.

PIPETTES -— Class A, 2.0-mL and 4.0-mL glass, or adjustable volume dispensers.
VOLUMETRIC FLASKS - Class A, sug gested sizes include 5 mL, 10 mL, 100 mL.
MICRO SYRINGES - Various sizes.

BALANCE - Analytical, capable of weighing to the nearest 0.0001 g.
DIAZOMETHANE GENERATOR - See Figure 4 fora diagram of an all glass
system custom made for these validation studies. Micro molar generators are also

available from commercial sources (Aldrich Cat.#: Z10,889-8 or equivalent).

GAS CHROMATOGRAPH -— Capillary GC (Hewlett Packard Model 6890 or

515.4-8


10.3

calibration range are relatively constant (<30% RSD). Average RRF is
determined by calculating the mean RRF of a minimum of five calibration
concentrations.

10.2.5 Acceptance criteria for the calibration of each analyte is determined by
calculating the concentration of each analyte and surrogate in each of the
analyses used to generate the calibration curve or average RRF. Each
calibration point, except the lowest point, for each analyte must calculate to be
70-130% of its true value. The lowest point must calculate to be 50-150% of
its true value. If this criteria cannot be met, reanalyze the calibration
standards, restrict the range of calibration, or select an alternate method of
calibration.

CONTINUING CALIBRATION CHECK (CCC) — An appropriate number of CCCs
must be prepared with each extraction batch. The CCC verifies the initial calibration
at the beginning and end of each group of analyses, and after every 10" sample
during analyses. In this context, a “sample” is considered to be a field sample. LRBs,
LFMs, LFMDs and CCCs are not counted as samples. The beginning CCC for each
analysis batch must be at or below the MRL in order to verify instrument sensitivity
prior to any analyses. If standards have been prepared such that all low CAL points
are not in the same CAL solution, it may be necessary to analyze two CAL solutions
to meet this requirement. Subsequent CCCs should alternate between a medium and
high concentration.

10.3.1 Inject an aliquot of the appropriate concentration calibration check standard
solution prepared with the extraction batch and analyze with the same
conditions used during the initial calibration.

10.3.2 Calculate the concentration of each analyte and surrogate in the check
standard. The calculated amount for each analyte for medium and high level
CCCs must be + 30% of the true value. The calculated amount for the lowest
calibration level for each analyte must be within + 50% of the true value. If
these conditions do not exist, then all data for the problem analyte must be
considered invalid, and remedial action should be taken which may require
recalibration. Any field sample extracts that have been analyzed since the last
acceptable calibration verification should be reanalyzed after adequate
calibration has been restored, with the following exception. If the continuing
calibration fails because the calculated concentration is greater than 130%
(150% for the low-level CCC) for a particular target compound, and field
sample extracts show no detection for that target compound, non-detects may
be reported without re-analysis.

515.4-22


TABLE 11. SAMPLE HOLDING TIME DATA FOR SAMPLES FROM A
CHLORINATED SURFACE WATER FORTIFIED WITH METHOD

ANALYTES*
Day0 Day2 Day7 Day14
Compound %Ree %Rec %Rec %Rec
Dalapon 91 90 91 108
3,5-Dichlorobenzoic acid 98 97 85 91
Dicamba 92 92 96 99
Dichlorprop 89 88 91 95
2,4-D 88 85 87 92
Pentachlorophenol 92 85 86 93
Silvex 91 88 86 94
2,4,5-T 89 89 85 91
2,4-DB 87 84 86 93
Chloramben 86 86 88 100
Dinoseb 105 95 99 111
Bentazon 91 87 95 99
Dacthal 92 91 86 94
Quinclorac 90 80 84 91
Picloram 94 85 85 99
Acifluorfen 109 96 103 123

* All samples fortified at the same level used to collect the mid level precision and
accuracy data (see Table 10 for example).

515.4-39


TABLE 12. EXTRACT HOLDING TIME DATA FOR SAMPLES FROM A
CHLORINATED SURFACE WATER FORTIFIED WITH METHOD

ANALYTES”
Initial *” Day 21
Compound Injection _Reinjection
Rec %Rec

Dalapon 100 89
3,5-Dichlorobenzoic acid 104 113
Dicamba 102 104
Dichlorprop 100 101
2,4-D 101 102
Pentachlorophenol 100 102
Silvex 101 103
2,4,5-T 99 102
2,4-DB 101 102
Chloramben 102 105
Dinoseb 99 81
Bentazon 98 100
Dacthal 99 103
Quinclorac 105 127
Picloram 107 98
Acifluorfen 92 104
2,4-Dichlorophenylacetic acid 106 105
(SUR)

“Sample storage stability is expressed as a percent recovery (%Rec) value calculated as
described in Section 9.9.2: P P ry (Rec)

PAIl samples fortified at the same level used to collect the mid level precision and
accuracy data (see Table 10 for example).

515.4-40


16.

REFERENCES

1. Glaser, J.A., Foerst, D.L., McKee, G.D., Quave, S.A., and Budde, W.L, “Trace
Analyses for Wastewaters,” Environ. Sci. Technol., 15 (1981) 1426-1435.

2. Giam, C.S., Chan, H.S., and Nef, G.S., "Sensitive Method for Determination of
Phthalate Ester Plas ticizers in Open-Ocean Biota Samples," Analytical Chemistry,47,
2225 (1975).

3. Giam, C.S., and Chan, H.S., "Control of Blanks in the Analysis of Phthalates in Air
and Ocean Biota Samples," U.S. National Bureau of Standards, Special Publication
442, 701-708, (1976).

4. "OSHA Safety and Health Standards, General Industry," (29CRF1910). Occupational
Safety and Health Administration, OSHA 2206, (Revised, Jan.1976).

5. “Carcinogens-Working with Carcinogens,” Publication No. 77-206, Department of
Health, Education, and Welfare, Public Health Service, Center for Disease Control,
National Institute of Occupational Safety and Health, Atlanta, Georgia, August 1977.

6. “Safety In Academic Chemistry Laboratories,” 3rd Edition, American Chemical
Society Publication, Committee on Chemical Safety, Washington, D.C., (1979).

7. ASTM Annual Book of Standards, Part II, Volume 11.01, D3370-82, "Standard
Practice for Sampling Water," American Society for Testing and Materials,
Philadelphia, PA, 1986.

8. Bassett, M.V.; Pepich, B.V. and Munch, D.M., “The Role Playedby Basic Hydrolysis

in the Validity of Acid herbicide Data - Recommendations for Future Preparation of
Herbicide Performance Evaluation Standards.” Environ. Sci. Technol., Vol.34, 1117,
(2000).

515.4-28


3.2

3.3

3.4

3.5

3.6

3.7

3.8

samples) extracted together by the same person(s) during a work day using the same
lots of solvents, surrogate solution, and fortifying solutions. Required QC samples
include Laboratory Reagent Blank, Laboratory Fortified Matrix, and either a Field
Duplicate or Laboratory Fortified Matrix Duplicate.

ANALYSIS BATCH — A set of samples that is analyzed on the same instrument
during a 24-hour period that begins and ends with the analysis of the appropriate
Continuing Calibration Check standards (CCC). Additional CCCs may be required.
depending on the length of the analysis batch and/or the number of Field Samples.

INTERNAL STANDARD (IS) — A pure analyte added to an extract or standard
solution in a known amount and used to measure the relative responses of other
method analytes and surrogates. The internal standard must be an analyte that is not a
sample component.

SURROGATE ANALYTE (SUR) - A pure analyte, which is extremely unlikely to be
found in any sample, and which is added to a sample aliquot in a known amount
before extraction or other processing, and is measured with the same procedures used
to measure other sample components. The purpose of the SUR is to monitor method
performance with each sample.

LABORATORY REAGENT BLANK (LRB) — An aliquot of reagent water or other
blank matrix that is treated exactly as a sample including exposure to all glassware,
equipment, solvents, reagents, sample preservatives, internal standards, and surrogates
that are used in the extraction batch. The LRB is used to determine if method
analytes or other interferences are present in the laboratory environment, the reagents,
or the apparatus.

LABORATORY FORTIFIED BLANK (LFB) — An aliquot of reagent water or other
blank matrix to which known quantities of the method analytes and all the
preservation compounds are added. The LFB is analyzed exactly like a sample, and
its purpose is to determine whether the methodology is in control, and whether the
laboratory is capable of making accurate and precise measurements.

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) — An aliquot of an
environmental sample to which known quantities of the method analytes and all the
preservation compounds are added in the laboratory. The LFM is analyzed exactly
like a sample, and its purpose is to determine whether the sample matrix contributes
bias to the analytical results. The background concentrations of the analytes in the
sample matrix must be determined in a separate aliquot and the measured values in
the LFM corrected for background concentrations.

LABORATORY FORTIFIED SAMPLE MATRIX DUPLICATE (LFMD) - A

515.4-4


FIGURE 3
CHROMATOGRAM OF THE CHLORPHENOXY HERBICIDES ON A CONVENTIONAL PRIMARY COLUMN
(30 m x 250 um) CHROMATOGRAPHIC CONDITIONS ARE GIVEN IN TABLE 3.

1804 .
q 6

a
o

ud

b
fa)

nv
fa]

100:

o
fa}
to

o
5

b
D

wibiti tit

As EBED ROLES REED OBER BOEES LOSER REGED LOSES BREED CELE BOEES EREES RESOS LOSES RESUS ERE LSB RLES BESS EROS LADS RR OU ELE ER SL
15 16 V7 18 13 zo Z1 22 23 24 25 ZB

515.4-47


FIGURE 1
CHROMATOGRAM OF THE CHLORPHENOXY HERBICIDES ON A RTX-1701 COLUMN
CHROMATOGRAPHIC CONDITIONS ARE GIVEN IN TABLE 1.

4+
Hy

22800 4 15 iF

2cccd 4 |

In

ia

7800 4

18

he |
oot I
: ae fr La Ay yee

8000 5 | | 4
1 |

200 4 | i
| | i!

T T T T T T
. 4 13 min

af
wo
Ss
is
a

515.4-45


8.3

8.4

8.2.4 After collecting the sample, seal the bottle and agitate by hand for 15 seconds.

SAMPLE SHIPMENT AND STORAGE - All samples should be iced during
shipment and must not exceed 10 °C during the first 48 hours after collection.
Samples should be confirmed to be at or below 10 °C when they are received at the
laboratory. Samples stored in the lab must be held at or below 6 °C and protected
from light until extraction. Samples should not be frozen.

SAMPLE AND EXTRACT HOLDING TIMES - Because of the several pH
adjustments made to the samples in the course of this method, the addition of organic
or inorganic biocides, including hydrochloric acid, have been omitted. The analyst
should be aware of the potential for the biological degradation of the analytes.
Accordingly, samples should be extracted as soon as possible. Samples must be
extracted within 14 days. Extracts must be stored at < 0°C or less and protected from
light in glass vials with PTFE lined caps. Holding time studies indicate that the
analytes are stable for up to 21 days in the extracts.

QUALITY CONTROL

9.1

9.2

Quality control (QC) requirements include the Initial Demonstration of Capability
(Sect. 17, Table 13), the determination of the Detection Limit, and subsequent
analysis in each analysis batch of a Laboratory Reagent Blank (LRB), Continuing
Calibration Check Standards (CCC), a Laboratory Fortified Sample Matrix (LFM),
and either a Laboratory Fortified Sample Matrix Duplicate (LFMD) or a Field
Duplicate Sample. This section details the specific requirements for each QC
parameter. The QC criteria discussed in the following sections are summarized in
Section 17, Tables 13 and 14. These criteria are considered the minimum acceptable
QC criteria, and laboratories are encouraged to institute additional QC practices to
meet their specific needs.

9.1.1 Process all quality control samples through all steps of Section 11, including
hydrolysis and methylation. Sample preservatives as described in Section 8.1
must be added prior to extracting and analyzing the quality control samples.

INITIAL DEMONSTRATION OF CAPABILITY (IDC) — Requirements for the
Initial Demonstration of Capability are described in the following sections and
summarized in Section 17, Table 13.

9.2.1 INITIAL DEMONSTRATION OF LOW SYSTEM BACKGROUND —
Before any samples are analyzed, it must be demonstrated that a laboratory
reagent blank (LRB) is reasonably free of contamination and that the criteria
in Section 9.4 are met. Process all quality control samples through all all steps
of the method (Sect. 9.1.1).

515.4-15


9.3

9.4

9.5

9.6

9.7

Minimum Reporting Level (MRL) — The MRL is the threshold concentration of an
analyte that a laboratory can expect to accurately quantitate in an unknown sample.
The MRL should not be established at an analyte concentration that is less than either
three times the Detection Limit or a concentration which would yield a response less
than a signal-to-noise (S/N) ratio of five. Depending upon the study’s data quality
objectives it may be set at a higher concentration. Although the lowest calibration
standard must be at or below the MRL, the MRL must never be established at a
concentration lower than the lowest calibration standard.

LABORATORY REAGENT BLANK (LRB) — An LRB is required with each
extraction batch (Sect. 3.1) of samples to determine the background system
contamination. If the LRB produces a peak within the retention time window of any
analyte that would prevent the determination of that analyte, determine the source of
contamination and eliminate the interference before processing samples. Background
contamination must be reduced to an acceptable level before proceeding. Background
from method analytes or contaminants that interfere with the measurement of method
analytes must be below 1/3 of the MRL. If the target analytes are detected in the LRB
at concentrations equal to or greater than this level, then all data for the problem
analyte(s) must be considered invalid for all samples in the extraction batch.

CONTINUING CALIBRATION CHECK (CCC) — A standard prepared in the same
extraction batch as the samples of interest that contains all compounds of interest and
is extracted in the same manner as the procedural standards used to prepare the initial
calibration curve. Calibration checks, prepared with the samples being analyzed, are
required at the beginning of each day that samples are analyzed, after every ten
samples, and at the end of any group of sample analyses. See Section 10.3 for
concentration requirements, frequency requirements, and acceptance criteria.

LABORATORY FORTIFIED BLANK (LFB) - Since this method utilizes procedural
calibration standards, which are fortified reagent waters, there is no difference
between the LFB and the continuing calibration check standard. Consequently, the
analysis ofan LFB is not required ; however the acronym LFB is used for clarity in
the IDC.

INTERNAL STANDARDS (IS) - The analyst must monitor the peak area of each
internal standard in all injections during each analysis day. The IS response (as
indicated by peak area) for any chromatographic run must not deviate by more than +
50% from the average area measured during the initial calibration for that IS. A poor
injection could cause the IS area to exceed these criteria. Inject a second aliquot of
the suspect extract to determine whether the failure is due to poor injection or
instrument response drift.

515.4-17


2.

3.

1.2

1.3

1.4

This method is also applicable to the determination of salts and esters of analyte
acids. The form of each acid is not distinguished by this method. Results are
calculated and reported for each listed analyte as the total free acid. This method is
able to quantify the mono- and di-acid forms of Dacthal but not the parent compound.

Detection Limits are compound, instrument, and matrix dependent. The Detection
Limit is defined as the statistically calculated minimum amount that can be measured.
with 99% confidence that the reported value is greater than zero.” Experimentally
determined Detection Limits for the above listed analytes are provided in Section 17,
Table 4. The Detection Limit differs from, and is usually lower than (but never
above), the minimum reporting level (MRL) (Sect. 3.17). The concentration range
for target analytes in this method was evaluated between 0.5 ug/L and 20 ug/L for a
40-mL sample. Precision and accuracy data are presented in Section 17, Tables 5 -
10.

This method is restricted to use by or under the supervision of analysts skilled in
liquid-liquid extractions, derivatization procedures and the use of GC and
interpretation of gas chromatograms. The method was developed using fast GC but
“conventional” GC may be used as long as the laboratory meets the requirements of
the IDC (Sect. 9.2).

SUMMARY OF METHOD

2.1

A 40-mL volume of sample is adjusted to pH = 12 with 4 N sodium hydroxide and
allowed to sit for one hour at room temperature to hydrolyze derivatives. Following
hydrolysis, a wash step using a hexane:MtBE mixture is performed as a sample
cleanup and to remove Dacthal. The aqueous sample is then acidified with sulfuric
acid to a pH of less than 1 and extracted with 4-mL of methyl tert-butyl ether (MtBE).
The chlorinated acids that have been partitioned into the MtBE are then converted to
methyl esters by derivatization with diazomethane. The target esters are separated
and identified by fast capillary column gas chromatography using an electron capture
detector (GC/ECD). Analytes are quantified using a procedural standard calibration
technique with an internal standard.

NOTE: since many of the analytes contained in this method are applied as a variety of
esters and salts, it is imperative to hydrolyze them to the parent acid prior to
extraction.

DEFINITIONS

3.1

EXTRACTION BATCH - A set of up to 20 field samples (not including QC

515.4-3


TABLE 10: MID LEVEL PRECISION AND ACCURACY IN FORTIFIED CHLORINATED
GROUND WATER

Fortification Mean%  % RSD

Compound Level (ug/L) Recovery (n=7)
Dalapon 10 97 5.5
3,5-Dichlorobenzoic acid 5.0 95 2.1
Dicamba 5.0 98 1.6
Dichlorprop 10 719 0.7
2,4-D 10 99 1.6
Pentachlorophenol 1.0 100 4.2
Silvex 2.5 97 1.6
2,4,5-T 2.5 97 1.5
2,4-DB 10 92 11
Chloramben 5.0 102 2.6
Dinoseb 10 105 2.6
Bentazon 10 101 1.8
Dacthal 5.0 99 1.2
Quinclorac 1.0 94 15
Picloram 10 103 2.5
Acifluorfen 5.0 84 2.5
2,4-Dichlorophenylacetic acid (SUR) 25 106 11

515.4-38


12.

11.4.2 Establish an appropriate retention time window for each target and surrogate
to identify them in the QC and field samples. This should be based on
measurements of actual retention time variation for each compound in
standard solutions analyzed on the GC over the course of time. Plus or minus
three times the standard deviation of the retention time for each compound
while establishing the initial calibration and completing the IDC can be used
to calculate a suggested window size; however, the experience of the analyst
should weigh heavily on the determination of the appropriate retention
window size.

11.4.3 Check system calibration by analyzing a CCC (Sect. 10.3) and calibrate the
system by either the analysis of a calibration curve (Sect. 10. 2) or by
confirming the initial calibration is still valid by analyzing a continuing
calibration check as described in Section 10.3. Begin analyzing field and QC
samples at their appropriate frequency by injecting the same size aliquots
under the same conditions used to analyze the initial calibration.

11.4.4 An analyst must not extrapolate beyond the established calibration range. If
an analyte result exceeds the range of the initial calibration curve, the extract
may be diluted with MtBE containing the internal standard (Sect. 7.2.1.3), and
the diluted extract injected. Acceptable surrogate performance (Sect. 9.8)
should be determined from the undiluted sample extract. Incorporate the
dilution factor into final concentration calculations. The dilution will also
affect analyte MRLs.

DATA ANALYSIS AND CALCULATION

12.1

12.2

12.3

12.4

Identify the method analytes in the sample chromatogram by comparing the retention
time of the suspect peak to retention time of an analyte peak in a calibration standard.
Surrogate retention times should be confirmed to be within acceptance limits (Sect.
11.4.2) even if no target compounds are detected.

Calculate the analyte concentrations using the initial calibration curve generated as
described in Section 10.2. Quantitate only those values that fall between the MRL
and the highest calibration standard. Samples with target analyte responses that
exceed the highest standard require dilution and reanalysis (Sect. 11.4.4).

Analyte identifications should be confirmed using the confirmation column specified
in Table 2 or another column that is dissimilar to the primary column or by GC/MS if

the concentrations are sufficient.

Adjust the calculated concentrations of the detected analytes to reflect the initial

515.4-26


METHOD 515.4

DETERMINATION OF CHLORINATED ACIDS IN DRINKING

WATER BY LIQUID-LIQUID MICROEXTRACTION,

DERIVATIZATION, AND FAST GAS CHROMATOGRAPHY WITH

ELECTRON CAPTURE DETECTION

1. SCOPE AND APPLICATION

11

This is a fast gas chromatography (GC) method for the determination of chlorinated
acids in drinking waters. Accuracy, precision, and Detection Limit data have been
generated for the following compounds in reagent water and finished ground and

surface waters.

Analyte Chemical Abstracts Service
Registry Number

Acifluorfen® 50594-66-6
Bentazon 25057-89-0
Chloramben 133-90-4
2,4-D 94-75-7
Dalapon 75-99-0
2,4-DB 94-82-6
Dacthal acid metabolites”

Dicamba 1918-00-9
3,5-Dichlorobenzoic acid 51-36-5
Dichlorprop 120-36-5
Dinoseb 88-85-7
Pentachlorophenol 87-86-5
Picloram 1918-02-1
2,4,5-T 93-76-5
2,4,5-TP (Silvex) 93-72-1
Quinclorac 84087-01-4

© The herbicide Lactofen will be quantitated as Acifluorfen as their
structures represent different esters of the same acid herbicide.

® Dacthal mono-acid and di-acid metabolites are included in method
scope; Dacthal di-acid was used for validation studies.



TABLE 6: MID LEVEL PRECISION AND ACCURACY IN REAGENT WATER

Fortification Mean%  % RSD

Compound Level (ug/L) Recovery (n=7)
Dalapon 10 107 2.3
3,5-Dichlorobenzoic acid 5.0 96 2.3
Dicamba 5.0 102 1.5
Dichlorprop 10 107 0.6
2,4-D 10 106 1.4
Pentachlorophenol 1.0 103 14
Silvex 2.5 107 44
2,4,5-T 2.5 105 1.3
2,4-DB 10 93 1.6
Chloramben 5.0 105 29
Dinoseb 10 119 4.6
Bentazon 10 98 0.7
Dacthal 5.0 100 1.9
Quinclorac 1.0 101 2.9
Picloram 10 99 3.1
Acifluorfen 5.0 107 4.5
2,4-Dichlorophenylacetic acid (SUR) 25 112 1.3

515.4-34


TABLE 14: QUALITY CONTROL REQUIREMENTS (SUMMARY)

Method

Requirement Specification and Acceptance Criteria
Reference Frequency
Section 9.7 | Internal 4,4'-dibromooctafluoro- Peak area counts for the IS in LFBs,
Standard biphenyl is added to the LRBs, and sample extracts must be
(IS) extraction solvent. within 50-150% of the average peak
area calculated during the initial
calibration. If the IS does not meet
criteria, corresponding target results
are invalid.
Section 9.8 | Surrogate 2,4-dichlorophenylacetic | Surrogate recovery must be 70-130%
Standard acid is added to all of the true value. If surrogate fails
(SUR) calibration standards and __| this criterion, report all results for
samples, including QC sample as suspect/surrogate recovery.
samples.
Section 9.9 | Laboratory Analyze one LFM per Recoveries at mid and high levels not
Fortified analysis batch (20 within 70-130% or low-level
Sample samples or less) fortified | recoveries not within 50-150% of the
Matrix (LFM) | with method analytes at a | fortified amount may indicate a matrix
and concentration close to but | effect.
Laboratory greater than the native Target analyte RPDs for LFMD
Fortified concentration, should be within +30% at mid and
Matrix LFMD should beused in | high levels of fortification and within
Duplicate place of Field Duplicate if | +50% near MRL.
(LFMD) frequency of detects for
targets is low.
Section Field Extract and analyze at Target analyte RPDs for FD should be
9.10 Duplicates least one FD with each within +30% at mid and high levels of
(FD) extraction batch (20 fortification and within +50% near
samples or less). A MRL.
LFMD may be substituted
for a FD when the
frequency of detects for
target analytes is low.
Section Quality Analyzed when new Results must be 70-130% of the
9.11 Control Primary Dilution expected value.
Sample Standards (PDS) are
(QCS) prepared.

515.4-43



17. TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA

TABLE 1: CHROMATOGRAPHIC CONDITIONS AND AVERAGE RETENTION TIME
DATA FOR THE PRIMARY COLUMN (RTX-1701, 40m x 180 um i.d.)

Peak Number Average T,

(Figure 1) Compound (miny* % RSD
1 Dalapon 7.06 0.017
2 3,5 Dichlorobenzoic acid 11.32 0.002
3 2,4-Dichlorophenylacetic acid (SUR) 11.80 0.002
4 Dicamba 11.91 0.002
5 Dichlorprop 12.21 0.002
6 4,4'-Dibromooctafluorobiphenyl (IS) 12.25 0.002
7 2,4-D 12.37 0.002
8 Pentachlorophenol 12.49 0.002
9 Silvex 12.70 0.002
10 2,4,5-T 12.90 0.002
11 2,4-DB 13.10 0.003
12 Chloramben. 13.15 0.003
13 Dinoseb 13.44 0.003
14 Bentazon 13.60 0.003
15 Dacthal 13.68 0.002
16 Quinclorac 13.85 0.004
17 Picloram 14.02 0.003
18 Acifluorfen 15.20 0.004

“ The average retention time represents the average of 7 runs.

Primary Column:
DB-1701, 40 mx 0.180 mm id., 0.20 jm film thickness, injector temp. 200 ‘C, liner 2 mm straight siltek®
deactivated, injection volume 1 UL of 200 ng/mL (highest level component) standard, splitless injection hold to
1 min then purge @ 50 mL/min, detector temp 360 °C, detector make up gas nitrogen at 20 mL/minute.
Temperature program: 45 ‘C initial, program at 5 “C/minute to 80°C, Then 50 ‘C/minute to 220°C, Then 20
‘C/minute to 280°C and Hold for 3 min, Data collection via HP GC Chemstation at a rate of 20Hz.

Carrier gas; Hydrogen (UHP)

Detector makeup gas: Nitrogen (UHP)

515,.4-29


the inner walls of the volumetric, and weigh to the nearest
0.1 mg. Use a 10-uL syringe and immediately add 10.0 uL
of standard material to the flask by keeping the syringe
needle just above the surface of the acetone. Be sure that
the standard material falls dropwise directly into the
acetone without contacting the inner wall of the volumetric.
Calculate the concentration in milligrams per milliliter from
the net gain in weight. Dilute to volume, stopper, then mix
by inverting the flask several times.

7.2.3.2 PRIMARY DILUTION STANDARD (PDS) - Prepare the primary
dilution standard solution by combining and diluting stock standard
solutions with acetone. This primary dilution standard solution should
be stored at < 0 °C. As a guideline to the analyst, the analyte
concentrations used in the primary dilution standard solution during
method development are given below.

Analyte cola)
Acifluorfen 5.0
Bentazon 10
Chloramben 5.0
2,4-D 10
Dalapon 10
2,4-DB 10
Dacthal acid metabolites 5.0
Dicamba 5.0
3,5-Dichlorobenzoic acid 5.0
Dichlorprop 10
Dinoseb 10
Pentachlorophenol 1.0
Picloram 5.0
2,4,5-T 2.5
2,4,5-TP (Silvex) 2.5
Quinclorac 5.0

515.4-13


9.2.2

9.2.3

9.2.4

9.2.5

INITIAL DEMONSTRATION OF PRECISION -— Prepare, extract, and
analyze 4-7 replicate LFBs fortified at 5 ug/L, or near the mid-range of the
initial calibration curve. Process all quality control samples through all all
steps of the method (Sect. 9.1.1). The relative standard deviation (RSD) of the
results of the replicate analyses must be less than 20%.

INITIAL DEMONSTRATION OF ACCURACY - Using the same set of
replicate data generated for Section 9.2.2, calculate average recovery. The
average recovery of the replicate values must be within + 20% of the true
value.

DETECTION LIMIT -— Prepare, extract and analyze at least seven replicate
LFBs at a concentration estimated to be near the Detection Limit, over a
period of at least three days (both extraction and analysis should be conducted
over at least three days) using the procedure described in Section 11. Process
all quality control samples through all all steps of the method (Sect. 9.1.1).
The fortification level may be estimated by selecting a concentration with a
signal of 2 to 5 times the noise level but must be at or below the laboratory’s
MRL (Sect. 9.3). The appropriate concentration will be dependent upon the
sensitivity of the GC/ECD system being used. Sample preservatives as
described in Section 8.1 must be added to these samples. Calculate the
Detection Limit using the equation

Detection Limit = Sty 1,1 aipta=0.99)

where

tin-1,1-alpha 0.99) = Students t value for the 99% confidence level with n-
1 degrees of freedom,

n= number of replicates, and

S = standard deviation of replicate analyses.

NOTE: Calculated Detection Limits need only be less than 1/3 of the
laboratory’s MRL to be considered acceptable. Do not subtract blank values
when performing Detection Limit calculations. The Detection Limit is a
statistical determination of precision only.” If the Detection Limit replicates
are fortified at a low enough concentration, it is likely that they will not meet
precision and accuracy criteria, and may result in a calculated Detection Limit
that is higher than the fortified concentration

METHOD MODIFICATIONS - The analyst is permitted to modify GC
columns, GC conditions, internal standards or surrogate standards, but each
time such method modifications are made, the analyst must repeat the
procedures of the IDC (Sect. 9.2).

515.4-16