SEPA

United States
Environmental Protection
Agency

Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268

Research and Development

Test Method

Chromium, Dissolved
Hexavalent (Atomic
Absorption, Furnace
Technique)—Method 218.5

1. Scope and Application

1.1. This method covers the
determination of dissolved hexavalent
chromium (Cr®) in drinking and
surface waters. The method may also
be applicable to certain domestic and
industrial wastes after filtration
provided that potential interferring
substances are taken into account.
(See 4.1.)

1.2 The method may be used to
analyze samples containing from 5 to
100 yg of Cr° per liter. The range of
the method may be extended upward
by dilution.

2. Summary of Method

2.1 The method is based on the
separation of Cr® from the sample by
coprecipitation of lead chromate with
lead sulfate in a solution of acetic
acid. After separation, the supernate
is drawn off and the Cr® precipitate
resolubilized in nitric acid as trivalent
chromium (Cr**) and quantified by
furnace atomic absorption.

2.2 Hexavalent chromium may also
be analyzed by the chelation/
extraction technique (see Method
218.4 or the procedure described in
9.2 of the Atomic Absorption methods
found in this manual)

218.5-1 Dec. 1982

3. Sample Handling and
Preservation

3.1 For sample handling, cleaning
glassware and the filtration procedure
see part 4.1 of the Atomic Absorption
Method section of this manual.

3.2 The sample must not be
preserved by acidification, but instead
transported and stored until time of
analysis at 4°C

3.3. Stability of Cr** in environmental
samples is n ot completely understood
at this time. The chemical nature of
the sample matrix can have a definite
affect on the chemistry of chromium.
Therefore, the analysis should be
carried out as soon as possible but no
longer than 24 hours after collection.

4. Interferences

4.1. The possible interference from
other elements which form stable
chromates is not known at this time.

4.2 Samples with either sulfate or
chloride concentrations above 1000
mg/liter should be diluted before
analysis.

4.3 The potential reduction of Cr
from highly reductive substances
increases as pH is lowered, When
sulfites and sulfides are present the


7.4.5 Mixed standard solution V—
Antimony, boron, magnesium, silver,
and thallium.

NOTE 1: If the addition of silver
to the recommended acid combination
results in an initial precipitation,
add 15 mL of deionized distilled
water and warm the flask until the
solution clears. Cool and dilute to 100
mL with deionized, distilled water. For
this acid combination the silver con-
centration should be limited to 2
mg/L. Silver under these conditions
is stable in a tap water matrix
for 30 days. Higher concentrations
of silver require additional HCI.

7.5 Two types of blanks are required
for the analysis. The calibration blank
(3.13) is used in establishing the
analytical curve while the reagent
blank (3.12) is used to correct for
possible contamination resulting from
varying amounts of the acids used in
the sample processing.

7.5.1 The calibration blank is pre-
pared by diluting 2 mL of (1+1) HNOs
and 10 mL of (1+1) HCI to 100 mL
with deionized, distilled water. (See
Note 6.) Prepare a sufficient quantity
to be used to flush the system be-
tween standards and samples.

7.5.2 The reagent blank must con-
contain all the reagents and in the
same volumes as used in the pro-
cessing of the samples. The reagent
blank must be carried through the
complete procedure and contain the
same acid concentration in the final
solution as the sample solution
used for analysis.

7.6 In addition to the calibration
standards, an instrument check stan-
dard (3.7), an interference check
sample (3.8) and a quality control
sample (3.9) are also required for the
analyses.

7.6.1 The instrument check standard
is prepared by the analyst by com-
bining compatible elements at a con-
centration equivalent to the midpoint
of their respective calibration curves.
(See 12.1.1)

7.6.2 The interference check sample
is prepared by the analyst in the
following manner. Select a
representative sample which contains
minimal concentrations of the
analytes of interest by known con-
centration of interfering elements that
will provide an adequate test of the
correction factors. Spike the sample
with the elements of interest at the
approximate concentration of either
100 ug/L or 5 times the estimated

detection limits given in Table 1. (For
effluent samples of expected high
concentrations, spike at an
appropriate level.) If the type of
samples analyzed are varied, a
synthetically prepared sample may be
used if the above criteria and intent
are met. A limited supply of a
synthetic interference check sample
will be available from the Quality
Assurance Branch of EMSL-
Cincinnati. (See 12.1.2)

7.6.3 The quality control sample
should be prepared in the same acid
matrix as the calibration standards

at a concentration near 1 mg/L and in
accordance with the instructions
provided by the supplier. The Quality
Assurance Branch of EMSL-Cincinnati
will either supply a quality control
sample or information where one of
equal quality can be procured. (See
12.1.3)

8. Sample handling an
preservation

8.1 For the determination of trace
elements, contamination and loss are
of prime concern. Dust in the labora-
tory environment, impurities in
reagents and impurities on laboratory
apparatus which the sample contacts
are all sources of potential
contamination. Sample containers can
introduce either positive or negative
errors in the measurement of trace
elements by (a) contributing con-
taminants through leaching or surface
desorption and (b) by depleting
concentrations through adsorption.
Thus the collection and treatment of
the sample prior to analysis requires
particular attention. Laboratory
glassware including the sample bottle
(whether polyethylene, polyproplyene
or FEP-fluorocarbon) should be
thoroughly washed with detergent
and tap water; rinsed with (1+1) nitric
acid, tap water, (1+1) hydrochloric
acid, tap and finally deionized, distilled
water in that order (See Notes 2 and
3).

NOTE 2: Chromic acid may be useful to
remove organic deposits from glass-
ware; however, the analyst should be
be cautioned that the glassware must
be thoroughly rinsed with water to
remove the last traces of chromium.
This is especially important if chromium
is to be included in the analytical
scheme. A commercial product, NOCH-
ROMIX, available from Godax Labor-
atories, 6 Varick St., New York, NY
10013, may be used in place of
chromic acid. Chomic acid should not
be used with plastic bottles.

NOTE 3: If it can be documented through

Metals-5 Dec. 1982

an active analytical quality control
program using spiked samples and re-
agent blanks, that certain steps in the
cleaning procedure are not required for
routine samples, those steps may be
eliminated from the procedure

8.2 Before collection of the sample a
decision must be made as to the type
of data desired, that is dissolved,
suspended or total, so that the appro-
priate preservation and pretreatment
steps may be accomplished. Filtration,
acid preservation, etc., are to be per-
formed at the time the sample is
collected or as soon as possible
thereafter.

8.2.1 For the determination of dis-
solved elements the sample must be
filtered through a 0.45-um membrane
filter as soon as practical after collec-
tion. (Glass or plastic filtering appara-
tus are recommended to avoid possi-
ble contamination.) Use the first 50-
100 mL to rinse the filter flask. Dis-
card this portion and collect the
required volume of filtrate. Acidify the
filtrate with (1+1) HNOs to a pH of 2
or less. Normally, 3 mL of (1+1) acid
per liter should be sufficient to pre-
serve the sample.

8.2.2 For the determination of sus-
pended elements a measured volume
of unpreserved sample must be fil-
tered through a 0.45-um membrane
filter as soon as practical after
collection. The filter plus suspended
material should be transferred to a
suitable container for storage and/or
shipment. No preservative is required.

8.2.3 For the determination of total
or total recoverable elements, the
sample is acidified with (1+1) HNO3
to pH 2 or less as soon as possible,
preferable at the time of collection
The sample is not filtered before
processing.

9. Sample Preparation

9.1 For the determinations of dis-
solved elements, the filtered,
preserved sample may often be
analyzed as received. The acid matrix
and concentration of the samples and
calibration standards must be the
same. (See Note 6.) If a precipitate
formed upon acidification of the
sample or during transit or storage, it
must be redissolved before the
analysis by adding additional acid
and/or by heat as described in 9.3.

9.2 For the determination of sus-
pended elements, transfer the mem-
brane filter containing the insoluble
material to a 150-mL Griffin beaker
and add 4 mL conc. HNOs. Cover the


6. Data to be entered into STORET
must be reported as ug/L.

Precision and Accuracy

1. Precision and accuracy data are
noi available at this time.

Dec. 1982 273.2-2


H2SOa to pH <2

Total, 50 PG Fitter on site 24 Hrs.
Dissolved Cool, 4°C
H2SO« to pH <2
Silica 50 Ponly Cool, 4°C 28 Days
Sulfate 50 P.G Cool, 4°C 28 Days
Sultide 500 P.G Cool, 4°C 7 Days

add 2 mb zinc
acetaie plus NaOH

to pH >9
Sulfite 50 P.G None Req. Analyze
400 Organics Immediately
BOD 1000 P.G Cool, 4°C 48 Hrs.
cob 50 P.G Cool, 4°C 28 Days
H2SOz tp pH <2
Oil & Grease 1000 Gonly Cool, 4°C 28 Days
H2SO4
to pH <2
Organic carbon 25 P.G Cool, 4°C HCI 28 Days
or H2SO4 to pH <2
Phenolics 500 Gonly Cool, 4°C 28 Days
H2S04 to pH <2
MBAS 250 P.G Cool, 4°C 48 Hrs.
NTA 50 PG Cool, 4°C 24 Hrs.

‘More specific instructions for preservation and sampling are found with each
procedure as detailed in this manual. A general discussion on sampling water and
industrial wastewater may be found in ASTM, Part 31, p. 72-82 (1976) Method D-
3370.

? Plastic (P) or Glass (G). For metals, polyethylene with a polypropylene cap (no liner)
is preferred.

“Sample preservation should be performed immediately upon sample collection.
For composite samples each aliquot should be preserved at the time of collection.
When use of an automated sampler makes it impossible to preserve each aliquot,
then samples may be preserved by maintaining at 4°C until compositing and
sample splitting are completed.

“When any sample is to be shipped by common carrier or sent through the United
States Mails, it must comply with the Department of Transportation Hazardous
Materials Regulations (49 CFR Part 172). The person offering such material for
transportation is responsible for ensuring such compliance. For the preservation
requirements of Table 1, the Office of Hazardous Materials, Materials
Transportation Bureau, Department of Transportation has determined that the
Hazardous Materials Regulations do not apply to the following materials:
Hydrochloric acid (HCI) in water solutions at concentrations of 0.04% by weight or
less (pH about 1.96 or greater); Nitric acid (HNO) in water solutions at
concentrations of 0.15% by weight or less (pH about 1.62 or greater); Sulfuric acid
(H2SO.4) in water solutions at concentrations of 0.35% by weight or less (pH about
1.15 or greater); and Sodium hydroxide (NaOH) in water solutions at concentrations
of 0.080% by weight or less (pH about 12.30 or less).

Samples should be analyzed as soon as possible after collection. The times listed
are the maximum times that samples may be held before analysis and still
considered valid. Samples may be held for longer periods only if the permittee, or
monitoring laboratory, has data on file to show that the specific types of samples
under study are stable for the longer time, and has received a variance from the
Regional Administrator. Some samples may not be stable for the maximum time
period given in the table. A permittee, or monitoring laboratory, is obligated to hold
the sample for a shorter time if knowledge exists to show this is necessary to
maintain sample stability.

Should only be used in the presence of residual chlorine.

*Maximum holding time is 24 hours when sulfide is present. Optionally, all
samples may be tested with lead acetate paper before the pH adjustment in order to
determine if sulfide is present. If sulfide is present, it canbe removed by the addition
of cadmium nitrate powder until a negative spot test is obtained. The sample is
filtered and then NaOH is added to pH 12.

° Samples should be filtered immediately on-site adding preservative for dissolved
metals.

*For samples trom non-chlorinated drinking water suplies conc. H2SO. should be
added to lower sample pH to less than 2. The sample should be analyzed before 14
days.


sample aliquot taken for analysis
should be neutralized and aerated
before beginning

5. Instrument Parameters
(General)

5.1 Drying Time and Temp: 30 sec-
125°C.

5.2 Ashing Time and Temp: 30 sec-
1000°C.

5.3 Atomizing Time and Temp: 10
sec-2700°C

5.4 Purge Gas Atmosphere: Argon
5.5 Wavelength: 357.9nm

5.6 Other operating parameters
should be as specified by the
particular instrument manufacturer.

6. Special Apparatus

6.1 Glassware

6.1.1 Filtering flask, heavy wall, 1
liter capacity

6.1.2 Centrifuge tubes, heavy duty,
conical, graduated, glass stoppered,
10 mL capacity

6.1.3 Pasteur pipets, borosilicate
glass, 5 % inches.

6.2 Centrifuge: any centrifuge
capable of reaching 2000 rpm and
accepting the centrifuge tubes
described in 6.1.2 may be used

6.3 pH Meter: a wide variety of
instruments are commercially
available and suitable for this work.

6.4 Test Tube Mixer: any mixer
capable of thorough vortex is
acceptable.

7. Reagents

7.1 Lead Nitrate Solution: Dissolve
33.1 grams of lead nitrate, Pb(NOs)2
(analytical reagent grade), in deionized
distilled water and dilute to 100 mL.

7.2. Ammonium Sulfate Solution
Dissolve 2.7 grams of ammonium
sulfate, (NH4)2SO. (analytical reagent
grade), in deionized distilled water and
dilute to 100 mL.

7.3 Calcium Nitrate Solution:
Dissolve 11.8 grams of calcium
nitrate, Ca(NOs)2 - 4H20 (analytical
reagent grade}, in deionized distilled
water and dilute to 100 mL. 1 mL =
20 mg Ca.

7.4 Nitric Acid, conc.: Distilled
reagent grade or equivalent to
spectrograde quality.

7.5 Acetic Acid, Glacial: ACS
reagent grade.

7.5.1 Acetic Acid, 10% (v/v): Dilute
10 mL glacial acetic acid to 100 mL.
with deionized distilled water.

7.6 Ammonium Hydroxide, 10%
(v/v): Dilute 10 mL conc ammonium
hydroxide, NH«OH (analytical reagent
grade), to 100 mL with deionized
distilled water,

7.7 Hydrogen Peroxide, 30%: ACS
reagent grade.

7.8 Potassium Dichromate Standard
Solution: Dissolve 2.8285 grams of
dried potassium dichromate, K2Cr207
(analytical reagent grade), in deionized
distilled water and dilute to 1 liter. 1
mL = 1 mg Cr (1000 mg/L)

7.9 Trivalent Chromium Working
Stock Solution: To 50 mL of the
potassium dichromate standard
solution (7.8) add 1 mL of 30% H202
(7.7) and 1 mL conc. HNO3 (7.4) and
dilute to 100 mL with deionized
distilled water 1 mL = 0.5 mg Cr.
Prepare fresh monthly or as needed.

8. Calibration

8.1 At the time of analysis prepare a
blank and a series of at least four
calibration standards from the Cr*”
working stock (7.9) that will
adequately bracket the sample. The
normal working range covers a
concentration range of 5 to 100 ug
Cr/L. Add to the blank and each
standard 1 mL 30% H202 (7.7), 5 mL
CONC HNOs (7.4), and 1 mL calcium
nitrate solution (7.3) for each 100 mL
of prepared solution before diluting to
final volume. These calibration
standard should be prepared fresh
weekly or as needed

8.2 The listed instrumental
conditions (5.) and the stated
calibration concentration range are for
a Perkin-Elmer HGA-2100 based on
the use of a 20uL injection, continous
flow purge gas and non-pyrolytic
graphite. The use of simultaneous
background correction is required for
both calibration and sample analysis.

9. Procedure

9.1 Transfer a 50 mL portion of the
filtered sample to a 100mL Griffin
beaker and adjust to pH 3.5+0.3 by
adding 10% acetic acid dropwise.

Dec. 1982 218.5-2

Record the volume of acid added and
adjust the final result to account for
the dilution.

Note: Care must be exercised not to
take the pH below 3. If the pH is
inadvertently lowered to < 3, 10%
NH.OH (7.6) should be used to raise
the pH to above 3.

9.2 Pipet a 10 mL aliquot of the
adjusted sample into a centrifuge tube
(6.1.2). Add 100uL of the lead nitrate
solution (7.1), stopper the tube, mix the
sample and allow to stand for 3 min

9.3 After the formation of lead
chromate, retain the Cr°* complex in
solution by addition of 0.5 mL glacial
acetic acid (7.5). Stopper and mix.

9.4 To provide adequate lead sulfate
for coprecipitation add 100 mL
ammonium sulfate solution (7.2),
stopper and mix.

9.5 Place the stoppered centrifuge
tube in the centrifuge, making sure
that the tube is properly
counterbalanced. Start the centrifuge
and slowly increase the speed to
2000 rpm in small increments over a
period of 5 min. Centrifuge the sam-
ple at 2000 rpm for 10 min.

Note 2: The speed of the centrifuge
must be increased slowly to insure
complete coprecipitation.

9.6 After centrifuging remove the
tube and draw off the supernate using
the apparatus detailed in Figure 1. As
the pasteur pipet is lowered into the
tube the supernate is sucked into the
filtering flask. With care the supernate
can be withdrawn to within
approximately 0.1 mL above the
precipitate.

9.7 To the remaining precipitate add
0.5 mL conc HNOs (7.4), 100uL 30%
H202 (7.7) and 100uL calcium nitrate
solution (7.3). Stopper the tube and
mix using a vortex mixer to disrupt
the precipitate and solubilize the lead
chromate. Dilute to 10mL, mix and
analyze in the same manner as the
calibration standard (8.2).

9.8 For the general furnace
procedure and calculation, see
“Furnace Procedure” part 9.3 of the
Atomic Absorption Methods section of
this manual.

10. Verification

10.1 For every sample matrix
analyzed verification is necessary to
determine that neither a reducing
condition nor a chemical interference
affecting precipitation is present. This


EPA

United States
Environmental Protection
Agency

Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268

Research and Development

Test Method

Organic Carbon, Total

(low level)

(UV promoted, persulfate
oxidation)—Method 415.2

1. Scope and Application

1.1 This method covers the
determination of total organic carbon
in drinking water and other waters
subject to the limitations in 1.3 and
5.1

1.2. This instrument is designed for
a two-step operation to distinguish
between purgeable and nonpurgeable
organic carbon. These separate values
are not pertinent to this method

1.3 This method is applicable only to
the carbonaceous matter which is
either soluble or has a particle size of
0.2 mm or less.

1.4 The applicable range is from
approximately 50 yg/L to 10 mg/L.
Higher concentrations may be
determined by sample dilution.

2. Summary of Method

A sample is combined with 1 mL of
acidified persulfate reagent and
placed in a sparger. The sample is
purged with helium which transfers
inorganic CO2 and purgeable organics
to a COz scrubber. The COz is
removed with at least 99.9%
efficiency with a 2.5-minute purge.
The purgeable organics proceed
through a reduction system where the
gas stream is joined by hydrogen and
passed over a nickel catalyst which
converts the purgeable organic carbon
to methane. The methane is
measured by a flame ionization

415.2-1 Dec. 1982

detector. The detector signal is
integrated and displayed as the
concentration of purgeable organic
carbon.

The sample is then transferred to a
quartz ultraviolet reaction coil where
the nonpurgeable organics are
subjected to intense ultraviolet
illumination in the presence of the
acidified persulfate reagent. The
nonpurgeables are converted to CO2
and transferred to a second sparger
where a helium purge transfers the
COz to the reduction system and into
the detector. The signal is integrated,
added to the purgeable organic carbon
value, and displayed as the
concentration of total organic carbon.

3. Definitions

3.1. Total organic carbon measured
by this procedure is the sum of the
purgeable organic carbon and the
nonpurgeable organic carbon as
defined in 3.2 and 3.3.

3.2 Purgeable organic carbon is the
organic carbon matter that is
transferred to the gas phase when the
sample is purged with helium and
which passes through the COz
scrubber. The definition is instrument-
condition dependent.

3.3 Nonpurgeable organic carbon is
defined as that which remains after
removal of the purgeable organic
carbon from the sample containing
acidified persulfate reagent and which


SEPA

United States Environmental Monitoring and
Environmental Protection Support Laboratory
Agency Cincinnati OH 45268

Research and Development

Test Method

Sodium (Atomic
Absorption, furnace
technique)—Method 273.2

Optimum Concentration Range: 1-30 the calculation, see “Furnace
ug/L Procedure” 9.3 of the Atomic
Detection Limit: 0.2 ug/L Absorption method section of
Preparation of Standard Solution this manual.

1. Stock solution: Prepare as
described under “direct
aspiration method.”’

2. Prepare dilutions of the stock
solution to be used as calibration
standards at the time of analysis.
These solutions are also to be
used for ‘standard additions.’"

3. The calibration standard should
be diluted to contain 0.5% (v/v)

Notes
1. The above concentration values
and instrument conditions are
for a Perkin-Elmer HGA-2100,
based on the use of a 20 wl
injection, continuous flow purge
gas and non-pyrolytic graphite.

HNO. Smaller size furnace devices or
* those employing faster rates of
Sample Preservation atomization can be operated
1. For sample handling and preser- using lower atomization
vation, see part 4.1 of the Atomic temperatures for shorter time
Absorption Methods section of periods than the above
this manual. recommended settings.
Sample Preparation 2. Samples containing
1. Prepare as described under “di- concentrations higher than those
rect aspiration method”. Sample given in the optimum range
solutions for analysis should should be analyzed by either the
contain 0.5% (v/v) HNOs. direct aspiration method (Method
273.1) or the flame photometric
Instrument Parameters (General) method (Std. Methods, 14th
1. Drying Time and Temp: 30 sec @ Edition, p. 250).
125°C 3. Nitrogen may also be used as
2. Ashing Time and Temp: 30 sec @ the purge gas.
250°C 4. For every sample matrix
3. Atomizing Time and Temp: 10 sec analyzed, verification is
@ 2000°C. necessary to determine that
4. Purge Gas atmosphere: Argon method of standard addition is
5. Wavelength: 589.6 nm not required (see 5.2.1 of
6. Other operating parameters the Atomic Absorption method
should be set as specified by the section of this manual).
particular instrument 5. If method of standard addition is
manufacturer. required, follow the procedure
given earlier in 8.5 of the
Analysis Procedure Atomic Absorption methos
1. For the analysis procedure and section of this manual.

273.2-1 Dec. 1982


Table 2. Analyte Concentration Equivalents (mg/L) Arising From Interferents at the 100 mg/L Level
Analyte Wavelength, nm Interferent
Al Ca Cr Cu Fe Mg Mn Ni Ti Vv
Aluminum 308.215 - _ _ = _ = 0.21 _— = 1.4
Antimony 206.833 0.47 _ 29 - 0.08 _ _— _ 25 0.45
Arsenic 193.696 1.3 _ 0.44 = - _ _- _ _— wt
Barium 455.403 _ _ — - _ — - _ — _
Beryllium 313.042 = = ~ = = — _ _ 0.04 0.05
Boron 249.773 004 — = 0320 — = = — —
Cadmium 226.502 _ _ =— _ 0.03 _— — 0.02 _ —
Calcium 317.933 = - 008) = — 0.01 001 004 — 0.03 0.03
Chromium 267.716 _ _ = 0.003 — 004 — — 0.04
Cobalt 228.616 _ - 0.03 ad 0.005 — _ 0.03 0.15 _—
Copper 324.754 - _ = _ 0.003 — = — 05 0.02
fron 259.940 — — _ _ _— — 0.12 — - —
Lead 220.353 0.17 —- _— _ - — _ _ —
Magnesium 279.079 _ 0.02 0.11 _ 0.13 _ 0.25 _ 0.07 0.12
Manganese 257.610 0.005 = — 0.01 _ 0.002 0.002 — _ _ _
Molybdenum 202.030 005 — - - 0030 — - = = ~
Nickel 231.604 - - _ = - _ - - _ -
Selenium 196.026 0230 — - _ 0.09 = = - =
Silicon 288.158 _ - 0.07 _ - _ - - 0.07
Sodium 588.995 _— _ _ - - - - - 0.08 _
Thallium 190.864 0.30 _— _ oad - - _ - _ _
Vanadium 292.402 _ - 0.05 _ 0.005 — = _— 0.02 _
Zine 213.856 _ _ - 0.14 - _ = 0.29 = _—
Table 3. Interferent and Analyte Elemental Concen-
trations Used for Interference Measurements
in Table 2.
Analytes (mg/L) Interferents (mg/L)
Al 10 Al 1000
As 10 Ca 1000
B 10 Cr 200
Ba 7 Cu 200
Be 7 Fe 1000
Ca 1 Mg 1000
Ca 10 Mn 200
Co 1 Ni 200
Cr 1 Ti 200
Cu 1 Vv 200
Fe 1
Mg 1
Mn 1
Mo 10
Na 10
Ni 10
Pb 10
Sb 10
Se 10
Si 1
7 10
Vv 1
Zn 10
Metals-9 Dec. 1982


(

x

v4

EPA

United States
Environmental Protection
Agency

Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268

Research and Development

Test Method

Inductively Coupled Plasma—
Atomic Emission Spectrometric
Method for Trace Element
Analysis of Water and
Wastes—Method 200.7

1. Scope and Application

1.1 This method may be used for
the determination of dissolved,
suspended, or total elements in
drinking water, surface water,
domestic and industrial wastewaters.

1.2 Dissolved elements are
determined in filtered and acidified
samples. Appropriate steps must be
taken in all analyses to ensure that
potential interference are taken into
account. This is especially true when
dissolved solids exceed 1500 mg/L.
(See 5.)

1.3 Total elements are determined
after appropriate digestion procedures
are performed. Since digestion
techniques increase the dissolved
solids content of the samples,
appropriate steps must be taken to
correct for potential interference
effects. (See 5.)

1.4 Table 1 lists elements for which
this method applies along with
recommended wavelengths and
typical estimated instrumental
detection limits using conventional
pneumatic nebulization. Actual
working detection limits are sample
dependent and as the sample matrix
varies, these concentrations may also
vary. In time, other elements may be

Metals-1 Dec. 1982

added as more information becomes
available and as required.

1.5 Because of the differences
between various makes and models of
satisfactory instruments, no detailed
instrumental operating instructions
can be provided. Instead, the analyst
is referred to the instructions provided
by the manufacturer of the particular
instrument.

2. Summary of Method

2.1 The method describes a
technique for the simultaneous or
sequential multielement
determination of trace elements in
solution. The basis of the method is
the measurement of atomic emission
by an optical spectroscopic technique.
Samples are nebulized and the
aerosol that is produced is transported
to the plasma torch where excitation
occurs. Characteristic atomic-line
emission spectra are produced by a
radio-frequency inductively coupled
plasma (ICP). The spectra are
dispersed by a grating spectrometer
and the intensities of the lines are
monitored by photomultiplier tubes,
The photocurrents from the
photomultiplier tubes are processed
and controlled by a computer system.
A background correction technique is
required to compensate for variable
background contribution to the


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United States
Environmental Protection
Agency

Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268

Research and Development

Test Method

pH, Continuous Monitoring
(Electrometric)—Method 150.2

1. Scope and Application

1.1. This method is applicable to the
continuous pH measurement of
drinking, surface, and saline waters,
domestic and industrial waste waters.

2. Summary of Method

2.1 The pH of a sample is determined
electrometrically using a glass
electrode with a reference electrode
or a single combination electrode

3. Sample Handling and
Preservation

3.1. The composition of the water or
waste contacting the measuring
electrode system must be
representative of the total flow from
the water body.

4. Interferences

4.1. The glass electrode, in general,
is not subject to solution interferences
from color, turbidity, colloidal matter,
oxidants, reductants or high salinity.

4.2 Sodium error at pH levels
greater than 10 can be reduced or
eliminated by using a “low sodium
error” electrode.

4.3 Manually inspect the conditions
of the electrodes every 30 days for
coating by oily materials or buildup of
lime. If oil and grease and/or scale
buildup are not present, this time
interval may be extended.

4.3.1 Coatings of oil, grease and
very fine solids can impair electrode
response. These can usually be
removed by gentle wiping and

150.2-1 Dec. 1982

detergent washing. The use of flow-
through electrode housings which
provide higher flow velocity helps to
prevent the coating action.

4.3.2 Heavy particulate matter such
as lime accumulation can be removed
by careful scrubbing or immersion in
dilute (1+9) hydrochloric acid.
Continuous monitoring under these
conditions benefits from ultrasonic or
other in-line continuous cleaning
methods.

4.4 Temperature effects on the
electrometric measurement of pH
arise from two sources. The first is
caused by the change in electrode
output at various temperatures. This
interference can be controlled with
instruments having temperature
compensation or by calibrating the
electrode-instrument system at the
temperature of the samples. For best
results, meters having automatic
temperature compensation should be
calibrated with solutions within 5°C of
the temperature of the stream to be
measured. The second source is the
change of pH inherent in the sample
at various temperatures. This error is
sample dependent and cannot be
controlled, it should therefore be
noted by reporting both the pH and
temperature at the time of analysis.

5. Apparatus

5.1 pH Monitor - A wide variety of
instruments are commercially
available with various specifications
and optional equipment. For
unattended use, the monitor should
be equipped with automatic or fixed


Environmental Protection Agency
Regional Quality Assurance Coordinators

Region 1

Warren H. Oldaker

Central Regional Laboratory
Environmental Services Division

U.S. Environmental Protection Agency
60 Westview Street

Lexington, MA 02173
(617-861-6700)

FTS 8-617-861-6700

Region 2

Gerard F. McKenna

Research and QualityAssurance Branch
Environmental Services Division

US. Environmental Protection Agency
Edison, NJ 08837

(201-321-6645)

FTS 340-6645

Region 3

Charles Jones, Jr.

(3SA60)

Water Quality Monitoring Branch
Environmental Services Division

U.S. Environmental Protection Agency
6th & Walnut Streets, Curtis Bldg.
Philadelphia, PA 19106
(215-597-9162)

FTS 597-9162

Region 4

Wade Knight

Laboratory Services Branch
Environmental Services Division

US. Environmental Protection Agency
College Station Road

Athens, GA 30613

(404-546-3165)

FTS 250-3165

Region 5

David Payne

Quality Assurance Office
Environmental Services Division

U.S. Environmental Protection Agency
536 South Clark Street

Chicago, IL 60605

(312-353-7712)

FTS 353-7712

vi

Region 6
Eloy R. Lozano

Environmental Services Division

U.S. Environmental Protection Agency
1201 Elm St.,

First Int'l Bldg

Dallas, TX 75270

(214-767-2697)

FTS 729-2697

Region 7

Charles P. Hensley

Environmental Services Division

U.S. Environmental Protection Agency
25 Funston Road

Kansas City, KS 66115
(816-374-4285)

FTS 758-4285

Region 8

Dr. Juanita Hillman

Environmental Services Division

U.S. Environmental Protection Agency
Lincoln Tower Bldg., Suite 900

1860 Lincoln St.

Denver, CO 80295

(303-327-4935)

FTS 327-4935

Region 9

Dr. Ho Young

Office of Quality Assurance and Monitoring Systems

U.S, Environmental Protection Agency
215 Fremont St.,

San Francisco, CA 94105
(415-556-2647)

FTS 556-2647

Region 10

Barry Townes

Environmental Services Division

U.S. Environmental Protection Agency
1200 Sixth Avenue

Seattle, WA 98101

(206-442-1675)

FITS 399-1675


Table 4.

ICP Precision and Accuracy Data

Sample # 1 Sample #2 Sample #3
Mean Mean Mean
True Reported Mean True Reported Mean True Reported Mean
Value Value Percent Value Value Percent Value Value Percent
Element ug/L pg/L RSD ug/L ug/L RSD pg/L ug/t RSD
Be 750 733 6.2 20 20 9.8 180 176 5.2
Mn 350 345 27 15 15 67 100 99 3.3
Vv 750 749 1.8 70 69 29 170 169 Leu
As 200 208 75 22 19 23 60 63 17
Cr 150 149 38 10 10 18 50 50 3.3
Cu 250 235 5.1 11 11 40 70 67 7.9
Fe 600 594 3.0 20 19 15 180 178 6.0
Al 700 696 5.6 60 62 33 160 164 13
Ca 50 48 12 25 2.9 16 14 13 16
Co 500 512 10 20 20 4.1 120 108 21
Ni 250 245 5.8 30 28 7 60 55 14
Pb 250 236 16 24 30 32 80 80 14
Zn 200 201 5.6 16 19 45 80 82 9.4
Se 40 32 21.9 6 85 42 10 85 8.3
Not all elements were analyzed by all laboratories.
Dec. 1982 Metals-10


should be attainable in the range of
pH 6.0 to 8.0. Accuracy data for
continuous monitoring equipment
are not available at this time.

Bibliography

1, Annual Book of ASTM
Standards, Part 31, “Water”
Standard 1293-78, Method D, p. 226
(1981).

150.2-3 Dec. 1982


a

EPA

United States
Environmental Protection
Agency

Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268

Research and Development

Test Method

Acidity (Titrimetric)—

Method 305.2

1. Scope and Application

1.1 This method is applicable to
rain, surface and other waters of pH
less than 8.3.

1.2 This method is a measure of the
concentration of strong and weak
acids that react with hydroxyl ions.
This includes the dissolved gases that
are present.

1.3. The range of this method
depends on the volume of sample
titrated and upon the precision that
the increments of titrant can be
measured. If only 10 mL of sample is
available for analysis, it is necessary
to use a 50 wL syringe for dispensing
the titrant in order to achieve a
precision of less than 10 yeq/L.

2. Summary of Method

2.1 Samples are titrated with 0.02 N
carbonate free NaOH solution. The
end point is determined with a pH
meter. Results are reported as
microequivalents (yeq) per liter.

3. Sampling Handling and
Storage

3.1 The sample container must be
filled completely, sealed and stored at
4°C. Care must be taken to minimize
exposure of the sample to the
atmosphere. Open the sample
container immediately before analysis.

3.2 Analysis should be performed as
soon as possible after collection.

4. Comments

4.1 Samples with an initial pH
between 4.3 and 8.3 are subject to

305.2-1 Dec. 1982

error due to the loss or gain of
dissolved gases during sampling,
storage and analyses.

5. Apparatus

5.1 pH meter and electrode(s), see
Method 150.1 or 150.2.

5.2 Micro buret or micro syrings.

5.3 Teflon or glass magnetic stirring
bar.

5.4 Magnetic stirrer.

5.5 Beakers or flasks.

6. Reagents

6.1 Standard sodium hydroxide
solution, 1 N: Dissolve 40g NaOH in
250 mL distilled water. Cool and dilute
to 1 liter with COz free distilled water.
Store in a polyolefin bottle and fitted
with a soda lime tube or tight cap to
protect from atmospheric COz.

6.2 Standard sodium hydroxide
titrant, 0.02 N: Dilute 20.0 mL of 1 N
NaOH with CO>2-free distilled water to
1 liter. Store in rubber stoppered
bottle. Protect from atmospheric COz
by using a soda lime tube.
Standardize against an 0.02 N
potassium acid phthalate solution
prepared by dissolving 4.085 g of
anhydrous KHCgH4QOq in CO2 free
distilled water and diluted to 1:1

7. Procedure

7.1 Pipet an appropriate aliquot of
sample into beaker of flask containing
a small teflon on glass stirring bar.
Use extreme care to minimize the
sample surface disturbance.


United States Environmental Monitoring and
Environmental Protection Support Laboratory
Agency Cincinnati OH 45268

Research and Development EPA-600/4-82-055 Dec. 1982

SEPA Test Methods

Technical Additions to
Methods for Chemical
Analysis of Water and
Wastes


analyte concentrations also listed in
Table 3.

At present, information on the listed
silver and potassium wavelengths are
not available but it has been reported
that second order energy from the
magnesium 383.231 nm wavelength
interferes with the listed potassium line
at 766.491 nm.

5.1.2 Physical interferences are
generally considered to be effects
associated with the sample nebuliza-
tion and transport processes. Such
properties as change in viscosity and
surface tension can cause significant
inaccuracies especially in samples
which may contain high dissolved
solids and/or acid concentrations. The
use of a peristaltic pump may lessen
these interferences. If these types of
interferences are operative, they must
be reduced by dilution of the sample
and/or utilization of standard addition
techniques. Another problem which
can occur from high dissolved solids
is salt buildup at the tip of the
nebulizer. This affects aersol flow-rate
causing instrumental drift. Wetting
the argon prior to nebulization, the
use of a tip washer, or sample dilution
have been used to control this
problem. Also, it has been reported
that better control of the argon flow
rate improves instrument
performance. This is accomplished
with the use of mass flow controllers.

5.1.3 Chemical Interferences are
characterized by molecular compound
formation, ionization effects and
solute vaporization effects. Normally
these effects are not pronounced with
the ICP technique, however, if
observed they can be minimized by
careful selection of operating
conditions (that is, incident power,
observation position, and so forth), by
buffering of the sample, by matrix
matching, and by standard addition
procedures. These types of
interferences can be highly dependent
on matrix type and the specific
analyte element.

5.2. It is recommended that
whenever a new or unusual sample
matrix is encountered, a series of
tests be performed prior to reporting
concentration data for analyte
elements. These tests, as outlined in
5.2.1 through 5.2.4, will ensure the
analyst that neither positive nor
negative interference effects are
operative on any of the analyte el-
ements thereby distorting the
accuracy of the reported values.

§.2.1 Serial dilution—if the analyte
concentration is sufficiently high (min-

imally a factor of 10 above the instru-
mental detection limit after dilution),
an analysis of a dilution should agree
within 5 % of the original determina-
tion (or within some acceptable con-
trol limit (14.3) that has been estab-
lished for that matrix). If not, a
chemical or physical interference ef-
fect should be suspected.

5.2.2 Spike addition—The recovery
of a spike addition added at a
minimum level of 10X the in-
strumental detection limit (maximum
100X) to the original determination
should be recovered to within 90 to
110 percent or within the established
control limit for that matrix. If not, a
matrix effect should be suspected. The
use of a standard addition analysis
procedure can usually compensate for
this effect. Caution: The standard ad-
dition technique does not detect coin-
cident spectral overlap. If suspected,
use of computerized compensation, an
alternate wavelength, or comparison
with an alternate method is recom-
mended. (See 5.2.3)

§.2.3 Comparison with alternate
method of analysis—When investi-
gating a new sample matrix, compari-
son tests may be performed with other
analytical techniques such as atomic
absorption spectrometry, or other
approved methodology.

5.2.4 Wavelength scanning of
analyte line region—lf the appropriate
equipment is available, wavelength
scanning can be performed to detect
potential spectral interferences.

6. Apparatus

6.1 Inductively Coupled Plasma-
Atomic Emission Spectrometer.

6.1.1 Computer controlled atomic
emission spectrometer with background
correction.

6.1.2 Radiofrequency generator.

6.1.3 Argon gas supply, welding
grade or better.

6.2 Operating conditions — Because
of the differences between various
makes and models of satisfactory
instruments, no detailed operating
instructions can be provided. Instead,
the analyst should follow the
instructions provided by the
manufacturer of the particular
instrument. Sensitivity, instrumental
detection limit, precision, linear dy-
namic range, and interference effects
must be investigated and established
for each individual analyte line on that
particular instrument. It is the

Metals-3 Dec. 1982

responsibility of the analyst to verify
that the instrument configuration and
operating conditions used satisfy the
analytical requirements and to
maintain quality control data
confirming instrument performance
and analytical results.

7. Reagents and standards

7.1 Acids used in the preparation

of standards and for sample processing
must be ultra-high purity grade or
equivalent. Redistilled acids are
acceptable.

7.1.1 Acetic acid, conc. (sp gr 1.06).

7.1.2 Hydrochloric acid, conc. (sp gr
1.19).

7.1.3 Hydrochloric acid, (1+1): Add
500 mL conc. HCI (sp gr 1.19) to 400
mL deionized, distrilled water and
dilute to 1 liter.

7.1.4 Nitric acid, conc. (sp gr 1.41).

7.1.5 Nitric acid,(1+1): Add 500 mL
conc. HNOs (sp. gr 1.41) to 400 mL
deionized, distilled water and dilute to
1 liter.

7.2 Dionized, distilled water: Prepare
by passing distilled water through a
mixed bed of cation and anion ex-
change resins. Use deionized, distilled
water for the preparation of all
reagents, calibration standards and as
dilution water. The purity of this water
must be equivalent to ASTM Type tI
reagent water of Specification D 1193
(14.6).

7.3 Standard stock solutions may be
purchased or prepared from ultra high
purity grade chemicals or metals. All
salts must be dried for 1h at 105°C
unless otherwise specified.

(CAUTION: Many metal salts are ex-
tremely toxic and may be fatal if swal-
lowed. Wash hands thoroughly after
handling.) Typical stock solution pre-
paration procedures follow:

7.3.1 Aluminum solution, stock, 1
mL = 100 yg Al: Dissolve 0.100 g of
aluminum metal in an acid mixture of 4
mL of (1+1) HCI and 1 mL of conc. HNO3
in a beaker. Warm gently to effect
solution. When solution is complete,
transfer quantitatively to a liter flask,
add an additional 10 mL of (1+1) HCI
and dilute to 1,000 mL with deionized,
distilled water.

7.3.2 Antimony solution stock, 1 mL
= 100 yg Sb: Dissolve 0.2669 g K(SbO)
CaH4O¢ in deionized distilled water,
add 10 mL (1+1) HCI and dilute

to 1000 mL with deionized, distilled
water.


determination of trace elements.
Background must be measured
adjacent to analyte lines on samples
during analysis. The position selected
for the background intensity
measurement, on either or both sides
of the analytical line, will be
determined by the complexity of the
spectrum adjacent to the analyte line.
The position used must be free of
spectral interference and reflect the
same change in background

intensity as occurs at the analyte
wavelength measured. Background
correction is not required in cases of
line broadening where a background
correction measurement would
actually degrade the analytical result.
The possibility of additional
interferences named in 5.1 (and tests
for their presence as described in 5.2)
should also be recognized and
appropriate corrections made.

3. Definitions

3.1 Dissolved — Those elements
which will pass through a 0.45 ym
membrane filter.

3.2 Suspended — Those elements
which are retained by a 0.45 ym
membrane filter.

3.3 Total — The concentration
determined on an unfiltered sample
following vigorous digestion (9.3), or
the sum of the dissolved plus
suspended concentrations. (9.1 plus
9.2.)

3.4 Total recoverable — The
concentration determined on an
unfiltered sample following treatment
with hot, dilute mineral acid (9.4).

3.5 Instrumental detection limit —
The concentration equivalent to a
signal, due to the analyte, which is
equal to three times the standard
deviation of a series of ten replicate
measurements of a reagent blank
signal at the same wavelength

3.6 Sensitivity — The slope of the
analytical curve, i.e. functional
relationship between emission
intensity and concentration.

3.7 Instrument check standard — A
multielement standard of known
concentrations prepared by the
analyst to monitor and verify
instrument performance on a daily
basis. (See 7.6.1)

3.8 Interference check sample — A
solution containing both interfering
and analyte elements of known
concentration that can be used to

verify background and interelement
correction factors. (See 7.6.2)

3.9 Quality contro! sample — A
solution obtained from an outside
source having known, concentration
values to be used to verify the
calibration standards. (See 7.6.3}

3.10 Calibration standards — a
series of know standard solutions
used by the analyst for calibration of
the instrument (i.e., preparation of the
analytical curve). (See 7.4)

3.71 Linear dynamic range — The
concentration range over which the
analytical curve remains linear.

3.12 Reagent blank — A volume of
deionized, distilled water containing
the same acid matrix as the
calibration standards carried through
the entire analytical scheme. (See
7.5.2)

3.13 Calibration blank — A volume
of deionized, distilled water acidified
with HNOs and HCI. (See 7.5.1)

3.14 Method of standard addition —
The standard addition technique
involves the use of the unknown and
the unknown plus a known amount of
standard. (See 10.6.1)

4. Safety

4.1 The toxicity or carcinogenicity of
each reagent used in this method has
not been precisely defined; however,
each chemical compound should be
treated as a potential health hazard.
From this viewpoint, exposure to
these chemicals must be reduced to
the lowest possible level by whatever
means available. 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 material data
handling sheets should also be made
available to all personnel involved in
the chemical analysis. Additional
references to laboratory safety are
available and have been identified
(14.7, 14.8 and 14.9) for the
information of the analyst.

5. Interferences

5.1 Several types of interference
effects may contribute to inaccuracies
in the determination of trace
elements. They can be summarized as
follows:

5.1.1 Spectral interferences can be
categorized as 1) overlap of a spectral
line from another element; 2)

Dec. 1982 Metals-2

unresolved overlap of molecular band
spectra; 3) background contribution
from continuous or recombination
phenomena; and 4} background
contribution from stray light from the
line emission of high concentration
elements. The first of these effects
can be compensated by utilizing a
computer correction of the raw data,
requiring the monitoring and
measurement of the interfering
element. The second effect may
require selection of an alternate
wavelength. The third and fourth
effects can usually be compensated by
a background correction adjacent to
the analyte line. In addition, users of
simultaneous multielement
instrumentation must assume the
responsibility of verifying the absence
of spectral interference from an
element that could occur in a sample
but for which there is no channel in
the instrument array. Listed in Table 2
are some interference effects for the
recommended wavelengths given in
Table 1. The data in Table 2 are
intended for use only as a
rudimentary guide for the indication of
potential spectral interferences. For
this purpose, linear relations between
concentration and intensity for the
analytes and the interferents can be
assumed.

The interference information, which
was collected at the Ames Laboratory,
is expressed at analyte concentration
eqivalents (i.e. false analyte concen-
trations) arising from 100 mg/L of the
interferent element. The suggested use
of this information is as follows:
Assume that arsenic (at 193.696 nm)
is to be determined in a sample
containing approximately 10 mg/L of
aluminum. According to Table 2, 100
mg/L of aluminum would yield a false
signal for arsenic equivalent to
approximately 1.3 mg/L. Therefore,
10 mg/L of aluminum would result in
a false signal for arsenic equivalent to
approximately 0.13 mg/L. The reader
is cautioned that other analytical
systems may exhibit somewhat
different levels of interference than
those shown in Table 2, and that the
interference effects must be evaluated
for each individual system.

Only those interferents listed were
investigated and the blank spaces in
Table 2 indicate that measurable inter-
ferences were not observed for the
interferent concentrations listed in
Table 3. Generally, interferences were
discernible if they produced peaks or
background shifts corresponding to

2-5% of the peaks generated by the

"Ames Laboratory, USDOE, lowa State University,
Ames lowa 50011


temperature compensation and with a
recorder or alarm function:

5.2 Glass electrode - with shielded
cable between electrode and monitor
unless preamplification is used

5.3 Reference electrode - a
reference electrode with a constant
potential and with either a visible
electrolyte or viscous gel fill

NOTE 1: Combination electrodes in-
corporating both measuring and refer-
ence functions are convenient to use
and are available with solid, gel-type fil-
ling materials that require minimal
maintenance.

5.4 Temperature sensor - for
automatic compensator covering
general ambient temperature range

5.5 Electrode mounting - to hold
electrodes; may be flow through (for
small flows), pipe mounted or
immersion

6. Reagents

6.1 Primary standard buffer salts are
available from the National Bureau of
Standards and should be used in
situations where extreme accuracy is
required

6.1.1 Preparation of reference
solutions from these salts require
some special precautions and
handling’ such as low conductivity
dilution water, drying ovens, and
carbon dioxide free purge gas. These
solutions should be replaced at least
once each month

6.2 Secondary buffers may be
prepared from NBS salts or purchased
as a solution from commercial
vendors. Use of these commercially
available solutions, which have been
validated by comparison to NBS
standards, is recommended for
routine operation. These buffers may
be retained for at least six months if
kept stoppered.

7. Calibration

7.1 Immersion type electrodes -
easily removed from mourting.

7.1.1 The electrode should be
calibrated at a minimum of two points
that bracket the expected pH of the
water/waste and are approximately
three pH units or more apart.

‘National Bureau of Standards Special Publication
260.

7.1.2 Repeat calibration
adjustments on successive portions of
the two buffer solutions until readings
are within 0.05 pH units of the buffer
value. If calibration problems occur,
see 4.3

7.1.3 Because of the wide variety of
instruments available, no detailed
operating instructions are provided.
Instead, the analyst should refer to
the particular manufacturer's
instructions.

7.1.4 Calibration against two buffers
should be carried out at least daily. If
the pH of the fluid being measured
fluctuates considerably, the calibration
should be carried out more often.
Calibration frequencies may be
relaxed if historical data supports a
longer period between calibration.

7.2 Immersion type electrodes -
not easily removed from mounting.

7.2.1 Collect a grab sample of the
flowing material from a point as close
to the electrode as possible. Measure
the pH of this grab sample as quickly
as possible with a laboratory - type pH
meter. Adjust the calibration control
of the continuous monitor to the
reading obtained.

7.2.2 The temperature and condition
of the grab sample must remain
constant until its pH has been
measured by the laboratory pH meter
The temperature of the sample should
be measured and the temperature
compensator of the laboratory pH
meter adjusted

7.2.3 The laboratory - type pH meter
should be calibrated prior to use
against two buffers as outlined in 7.1

7.2.4 The continuous pH monitoring
system should be initially calibrated
against two buffers as outlined in 7.1
before being placed into service.
Recalibration (every 30 days) at two
points is recommended if at all
possible to ensure the measuring
electrode is in working order. If this is
not possible, the use of electrode
testing features for a broken or
malfunctioning electrode should be
considered when purchasing the
equipment

7.2.5 The indirect calibration should
be carried out at least once a day. If
the pH of the fluid being measured
fluctuates considerably, the calibration
should be carried out more often.
Calibration frequencies may be
relaxed if historical data support a
longer period between calibration.

Dec. 1982 180.2-2

7.2.6 \f the electrode can be
removed from the system, but with
difficulty, it should be directly
calibrated as in 7.1 at least once a
month

7.3 Flow-through type electrode -
easily removed from its mounting.

7.3.1 Calibrate using buffers as in
7.1. The buffers to be used may be
the process stream itself as one
buffer, and as a second buffer after
adjustment of pH by addition of an
acid or base. This will provide the
larger volumes necessary to calibrate
this type electrode.

7.3.2 Since the velocity of sample
flow-through a flow through electrode
can produce an offset error in pH
reading, the user must have data on
hand to show that the offset is known
and compensation has been
accomplished.

7.4 Flow-through type electrode -
not easily removed from its mounting.

7.4.1 Calibrate as in 7.2.

7.4.2 Quality contro! data must be
on hand to show the user is aware of
possible sample flow velocity effects.

8. Procedure

8.1 Calibrate the monitor and
electrode system as outlined in
Section 7

8.2 Follow the manufacturer's
recommendation for operation and
installation of the system.

8.3 In wastewaters, the electrode
may require periodic cleaning. After
manual cleaning, the electrode should
be calibrated as in 7.1 or 7.2 before
returning to service

8.4 The electrode must be placed so
that the water or waste flowing past
the electrode is representative of the
system.

9. Calculations

9.1 pH meters read directly in pH
units. Reports pH to the nearest 0.1
unit and temperature to the nearest
°C.

10. Precision and Accuracy

10.1 Because of the wide variability
of equipment and conditions and the
changeable character of the pH of
many process waters and wastes, the
precision of this method is probably
less than that of Method 150.1;
however, a precision of 0.1 pH unit


must be accomplished by analyzing a
second 10mL aliquot of the pH
adjusted filtrate (9.1) spiked with CrTM
(7.8). The amount of spike added
should double the concentration found
in the original aliquot. Under no
circumstance should the increase be
of less than 30ug Cr°"/L. To verify the
absence of an interference the spike
recovery shouid be between 85% and
115%.

10.2 If the addition of the spike
extends the concentration beyond the
range of the calibration curve, the
analysis solution should be diluted
with blank solution and the calculated
results adjusted accordingly.

10.3 If the verification indicates a
suppressive interference, the sample
should be diluted and reanalyzed.

11,

11.1 Nitrogen should not be used as
a purge gas because of possible CN
band interference

Analytical Notes

11.2 The use of pyrolytic graphite
should be avoided when possible.
Generally, pyrolytic graphite resulted
in a more limited analytical working
range and in some situations an
enhancement effect

11.3 Pipet tips have been reported
to be a possible source of
contamination. (See part 5.2.9 of the
Atomic Absorption Methods section of
this manual.)

11.4 The method of standard
addition should not be required in as
much as the Cr® has been separated
from the original sample solution and
redissolved in a uniform matrix having
an absorption response coincident to
the calibration curve

11.5 Data to be entered into
STORET (No. 01032) must be reported
as ug/L.

12. Precision and Accuracy

12.1 Ina single laboratory (EMSL)
using a mixed industrial-domestic
waste effluent containing 22 ug
Cr°/L and spiked with a
concentration of 50 ug Cr°*/L the
standard deviations were + 1.0 and +
2.7, respectively with a spike recovery
of 94%,

12.2 Recoveries of a 40 wg Cr°/L
spike in diluted tannery and plating
waste effluents were 96% and 93%,
respectively.

12.3 Using Cincinnati, Ohio tap
water spiked at concentrations of
5,10, and 50 ug Cr®*/L the standard
deviations were + 0.7, +0.6, and
~0.6, respectively. Spike recovery at
all three levels was 102%.

12.4 A 1000 pg Cr*"/L standard
solution analyzed by this method
yielded a result of 8 ug Cr°/L with a
relative standard deviation of 19%.

12.5 The data from 5 ug Cr°*/L tap
water spike was used to calculate
method detection limit (MDL) with
99% confidence as described in
“Trace Analyses for Wastewater,” J
Glaser, D. Foerst, G. McKee, S.
Quave, W. Budde, Environmental
Science and Technology, Vol. 15,
Number 12, page 1426, December
1981. The calculated MDL for
Cincinnati drinking water is 2.3 yg/L.

218.5-3 Dec. 1982


is converted to CO2 under the
instrument conditions.

3.4 The system blank is the value
obtained in 8.2 for an irradiated,
recirculated reagent distilled water
sample.

4. Sample Handling and
‘Preservation

4.1 Sampling and storage of
samples must be done in glass
bottles. Caution: Do not leave any
headspace in the sample bottle as
this may contribute to loss of
purgeable organics.

4.2 Because of the possibility of
oxidation or bacterial decomposition of
some components of aqueous
samples, the lapse of time between
collection of samples and start of
analysis should be kept to a minimum.
Also, samples should be kept cool
(4°C) and protected from sunlight and
atmospheric oxygen.

4.3 When analysis cannot be
performed within two hours from time
of sampling, the sample should be
acidified to pH 2 with H2SO.. Note:
HCI should not be used because it is
converted to chlorine during the
analysis. This causes damage to the
instrument.

5. Interferences

5.1 If a sample is homogenized to
reduce the size of the particulate
matter, the homogenizing may cause
loss of purgeable organic carbon, thus
yielding erroneously low results.

6. Apparatus

6.1 Apparatus for blending or
homogenizing samples: A household
blender or similar device that will
reduce particles in the sample to less
than 0.2 mm.

6.2 Apparatus for Total Organic
Carbon: The essential components for
the apparatus used in this method
are: A sparge assembly, flow
switching valves, a pyrolysis furnace,
quartz ultraviolet reactor coil, reducing
column, flame ionization detector,
electrometer and integrator. This
method is based on the Dohrmann
Envirotech DC-54 Carbon Analyzer.
Other instruments having similar
performance characteristics may be
used.

6.3 Sampling Devices: Any
apparatus that will reliably transfer
10 mL of sample to the sparger. A 50
mL glass syringe is recommended

when analyzing samples with easily
purgeable organics so as to minimize
losses.

7. Reagents

7.1 Reagent Distilled Water:
Distilled water used in preparation of
standards and for dilution of samples
should be ultra-pure to reduce the
magnitude of the blank. Carbon
dioxide-free, double distilled water is
recommended. The water should be
distilled from permanganate or be
obtained from a system involving
distillation and carbon treatment. The
reagent distilled water value must be
compared to a system blank
determined on a recirculated distilled
water sample. The total organic
carbon value of the reagent distilled
water should be less than 60 ug/L.
Purgeable organic carbon values of
the reagent distilled water should be
less than 4 yg/L.

7.2 Potassium hydrogen phthalate,
stock solution, 500 mg carbon /liter:
Dissolve 1.063 g of potassium
hydrogen phthalate (Primary Standard
Grade) in reagent distilled water (7.1)
and dilute to 1 liter.

7.3 Potassium hydrogen phthalate (2
mg/L): Pipet 4 mL of potassium
hydrogen phthalate stock solution
(7.2) into a one liter volumetric flask
and dilute to the mark with reagent
distilled water (7.1).

7.4 Potassium hydrogen phthalate (5
mg/L): Pipet 1 mL of potassium
hydrogen phthalate stock solution
(7.2) into a 100 mL volumetric flask
and dilute to the mark with reagent
distilled water (7.1).

7.5 Potassium hydrogen phthalate
(10 mg/L): Pipet 2 mL of potassium
hydrogen phthalate stock solution
(7.2) into a 100 mL volumetric flask
and dilute to the mark with reagent
distilled water (7.1).

7.6 Acidified Persulfate Reagent:
Place 100 mL of reagent distilled
water (7.1) in a container. Add 5 g of
potassium persulfate. Add 5 g (3 mL)
of concentrated (85%) phosphoric
acid.

7.7 Carbonate-bicarbonate, stock
solution, 1000 mg carbon/liter: Place
0.3500 g of sodium bicarbonate and
0.4418 g of sodium carbonate in a
100 mL volumetric flask. Dissolve with
reagent distilled water (7.1) and dilute
to the mark.

7.8 Carbonate-bicarbonate, standard
solution 50 mg/L: Place 5 ml of the

Dec. 1982 415.2-2

carbonate-bicarbonate stock solution
in a 100 mL volumetric flask and
dilute to the mark with reagent
distilled water (7.1)

8. Procedure

8.1 Allow at least 30 minutes
warm-up time. Leave instrument
console on continuously when in daily
use, except for the ultraviolet light
source, which should be turned off
when not in use for more than a few
hours.

8.2 Adjust all gas flows,
temperatures and cycle times to
manufacturer's specifications. Perform
the “System Cleanup and Calibration”
procedure in the manufacturer's
specifications each day. Recirculate a
sample of irradiated distilled water
until two consecutive readings within
10% of each other are obtained.
Record the last value for the system
blank. This value is a function of the
total instrument operation and should
not vary significantly from previous
runs. Reasons for significant changes
in the value should be identified.

8.3 Check the effectiveness of the
COz scrubber by analyzing the
carbonate-bicarbonate standard
solution(7.8). Add 1 mL of acidified
persulfate reagent (7.6) to 50 mL of
the solution. Transfer 10 mL of the
solution-with-reagent to the first
sparger and start the analysis cycle.
No response, or a very minor reading,
should be obtained from this solution.

8.4 Add 1 mL of acidified persulfate
reagent (7.6) to 50 mL of reagent
distilled water (7.1) blank, standards
7.3, 7.4, and 7.5 and the samples.

8.5 Calibrate the analyzer as
follows:

8.5.1 Run the reagent distilled water
(7.1) and 5.0 mg/L standard (7.4):
Transfer 10 mL of the solution-with-
reagent to the first sparger and start
analyzer cycle

Ignore the meter reading for the first
cycle

Transfer a second 10 mL of the
solution-with-reagent to the first
sparger and start the analysis cycle

Record the meter reading (see 9.1) of
the final carbon value for each of the
reagent distilled water (7.1) and the
standard (7.4).

lf the meter reading is more than 25%
above or below the calculated value of
standard 7.4, reanalyze the standard


Table 1. Recommendation for Sampling and Preservation of Samples
According to Measurement’
Vol.
Reg Holding
Measurement (mL) Container® Preservative®* Time®
100 Physical Properties
Color 50 P.G Cool, 4°C 48 Hrs.
Conductance 100 P.G Cool, 4°C 28 Days
Hardness 100 P.G HNOs to pH<2 6 Mos.
Odor 200 Gonly Cool, 4°C 24 Hrs.
pH 25 PG None Reg. Analyze
Immediately
Residue
Filterable 100 P.G Cool, 4°C 7 Days
Non-
Filterable 100 P.G Cool, 4°C 7 Days
Total 100 PG Cool, 4°C 7 Days
Volatile 100 P.G Cool, 4°C 7 Days
Settleable 17000 PG Cool, 4°C 48 Hrs.
Matter
Temperature 1000 P.G None Req. Analyze
Immediately
Turbidity 100 P.G Cool, 4°C 48 Hrs.
200 Metals
Dissolved 200 PG Filter on site 6 Mos.®
HNOs3 to pH <2
Suspended 200 Filter on site 6 Mos.
Total 100 P.G HNOs to pH <2 6 Mos.
Chromium’® 200 PG Cool, 4°C 24 Hrs.
Mercury
Dissolved 100 P.G Filter 28 Days
HNOs to pH <2
Total 100 PG HNOs to pH <2 28 Days
300 Inorganics, Non-Metallics
Acidity 100 PG Cool, 4°C 14 Days
Alkalinity 100 P.G Cool, 4°C 14 Days
Bromide 100 P.G None Req. 28 Days
Chloride 50 P.G None Req. 28 Days
Chlorine 200 P.G None Req. Analyze
Immediately
Cyanides 500 P.G Cool, 4°C 14 Days’
NaOH to pH >12
0.69 ascorbic acid®
Fluoride 300 PG None Req. 28 Days
lodide 100 P.G Cool, 4°C 24 Hrs.
Nitrogen
Ammonia 400 P.G Cool, 4°C 28 Days
/HeSO«4 to pH <2
Kjeldahl, Total 500 P.G Cool, 4°C 28 Days
H2S04 to pH <2
Nitrate plus
Nitrite 100 P.G Cool, 4°C 28 Days
H2S04 to pH <2
Nitrate? 100 P.G Cool, 4°C 48 Hrs.
Nitrite 50 PG Cool, 4°C 48 Hrs.
Dissolved Oxygen
Probe 300 G bottle and top None Req. Analyze
Immediately
Winkler 300 G bottle and top Fix on site 8 Hours
and store
in dark
Phosphorus
Ortho-
phosphate, 50 P.G Filter on site 48 Hrs.
Dissolved Cool, 4°C
Hydrolyzable 50 PG Cool, 4°C 28 Days
H2S0s to pH <2
Total 50 PG Cool, 4°C 28 Days


beaker with a watch glass and heat
gently. The wam acid will soon dis-
solve the membrane

Increase the temperature of the
hot plate and digest the material.
When the acid has nearly evaporated,
cool the beaker and watch glass and
add another 3 mL of conc. HNOs.
Cover and continue heating until the
digestion is complete, generally indi-
cated by a light colored digestate.
Evaporate to near dryness (2 mL), cool,
add 10 mL HCI (1+1) and 15 mL
deionized, distilled water per 100 mL
dilution and warm the beaker gently
for 15 min. to dissolve any precipi-
tated or residue material. Allow to
cool, wash down the watch glass and
beaker walls with deionized distilled
water and filter the sample to remove
insoluble material that could clog the
nebulizer. (See Note 4.} Adjust the
volume based on the expec:ed con-
centrations of elements present. This
volume will vary depending on the
elements to be determined (See Note
6}. The sample is now ready for
analysis. Concentrations so determined
shall be reported as “suspended.”
NOTE 4: In place of filtering, the
sample after diluting and mixing may
be centrifuged or allowed to settle by
gravity overnight to remove insoluble
material.

9.3 For the determination of total
elements, choose a measured, volume
of the well mixed acid preserved
sample appropriate for the expected
level of elements and transfer to a
Griffin beaker. (See Note 5.) Add 3 mL
of conc. HNOs. Place the beaker on

a hot plate and evaporate to near dry-
ness cautiously, making certain that
the sample does not boil and that no
area of the bottom of the beaker is
allowed to go dry. Cool the beaker and
add another 5 mL portion of conc.
HNOs. Cover the beaker with a watch
glass and return to the hot plate.
Increase the temperature of the hot
plate so that a gentle reflux action
occurs. Continue heating, adding addi-
tional acid as necessary, until the
digestion is complete (generally indi-
cated when the digestate is light

in color or does not change :n appear-
ance with continued refluxing.) Again,
evaporate to near dryness and cool
the beaker. Add 10 mL of 141 HCI
and 15 mL of deionized, distilled
water per 100 mL of final sclution
and warm the beaker gently for 15
min. to dissolve any precipitate or
residue resulting from evapcration.
Allow to cool, wash down the beaker
walls and watch glass with deionized
distilled water and filter the sample to
remove insoluble material that could

clog the nebulizer. (See Note 4.) Adjust
the sample to a predetermined volume
based on the expected concentrations
of elements present. The sample is
now ready for analysis (See Note 6).
Concentrations so determined shall be
reported as “total.”

NOTE 5: If tow determinations of
boron are critical, quartz glassware
should be use.

NOTE 6: If the sample analysis solution
has a different acid concentration
from that given in 9.4, but does not
introduce a physical interference or
affect the analytical result, the same
calibration standards may be used.

9.4 For the determination of total
recoverable elements, choose a mea-
sured volume of a well mixed, acid
preserved sample appropriate for the
expected level of elements and trans-
fer to a Griffin beaker. (See Note 5.)
Add 2 mL of (1+1) HNO3 and 10 mL
of (1+1) HCI to the sample and heat
on a steam bath or hot plate until! the
volume has been reduced to near 25
mL making certain the sample does
not boil. After this treatment, cool
the sample and filter to remove inso-
luble material that could clog the
nebulizer. (See Note 4.) Adjust the
volume to 100 mL and mix. The sample
is now ready for analysis. Concentra-
tions so determined shall be reported
as “total.”

10. Procedure

10.1 Set up instrument with proper
operating parameters established in
6.2. The instrument must be allowed
to become thermally stable before be-
ginning. This usually requires at least
30 min. of operation prior to calibra-
tion,

10.2 Initiate appropriate operating
configuration of computer.

10.3 Profile and calibrate instru-
ment according to instrument
manufacturer's recommended
procedures, using the typical mixed
calibration standard solutions
described in 7.4. Flush the system
with the calibration blank (7.5.1)
between each standard. (See Note 7.)
(The use of the average intensity of
multiple exposures for both
standardization and sample analysis
has been found to reduce random
error.)

NOTE 7: For boron concentrations
greater than 500 g/L extended flush
times of 1 to 2 min. may be required.

10.4 Before beginning the sample
run, reanalyze the highest mixed
calibration standard as if it were a

Dec. 1982 Metals-6

sample. Concentration values obtained
should not deviate from the actual
values by more than + 5 percent

(or the established contro! limits
whichever is lower). If they do, follow
the recommendations of the instru-
ment manufacturer to correct for this
condition.

10.5 Begin the sample run flushing
the system with the calibration blank
solution (7.5.1) between each sample.
(See Note 7.) Analyze the instrument
check standard (7.6.1) and the calibra-
tion blank (7.5.1) each 10 samples.

10.6 If it has been found that
method of standard addition are
required, the following procedure is
recommended.

10.6.1 The standard addition tech-
nique (14.2) involves preparing new
standards in the sample matrix by
adding known amounts of standard to
one or more aliquots of the processed
sample solution. This technique com-
pensates for a sample constituent that
enhances or depresses the analyte
signal thus producing a different slope
from that of the calibration standards.
It will not correct for additive inter-
ference which causes a baseline shift.
The simplest version of this technique
is the single-addition method. The
procedure is as follows. Two identical
aliquots of the sample solution, each
of volume V;, are taken. To the

first (labeled A) is added a small
volume V, of a standard analyte
solution of concentration cs. To the
second (labeled B) is added the same
volume Vs of the solvent. The analy-
tical signals of A and B are measured
and corrected for nonanalyte signals.
The unknown sample concentration
c, is calculated:

SpVsCs
(Sa - Se) Vx

where Sa and Sz are the analytical
signals (corrected for the blank) of
solutions A and B, respectively. Vs
and cs should be chosen so that Sa
is roughly twice Sg on the average. It
is best if Vs is made much less than
Vx, and thus cs is much greater than
cx, to avoid excess dilution of the
sample matrix. If a separation or
concentration step is used, the
additions are best made first and
carried through the entire procedure.
For the results from this technique to
be valid, the following limitations
must be taken into consideration:

1, The analytical curve must be linear.
2. The chemical form of the analyte
added must respond the same as the
analyte in the sample.

Cx =


Table 1. Recommended Wavelengths ' and Estimated Instrumentat
Detection Limits

Estimated detection

Element Wavelength, nm limit, ug/L?
Aluminum 308.215 45
Arsenic 193.696 53
Antimony 206.833 32
Barium 455.403 2
Beryllium 313.042 0.3
Boron 249.773 5
Cadmium 226.502 4
Calcium 317.933 10
Chromium 267.716 7
Cobalt 228.616 7
Copper 324.754 6
Jron 259.940 7
Lead 220.353 42
Magnesium 279.079 30
Manganese 257.610 2
Molybdenum 202.030 8
Nickel 231.604 15,
Potassium 766.491 see
Selenium 196.026 75
Silica (SiO2) 288.158 58
Silver 328.068 7
Sodium 588.995 29
Thallium 190.864 40
Vanadium 292.402 8
Zine 213.856 2

"The wavelengths listed are recommended because of their sensitivity and
overall acceptance. Other wavelengths may be substituted if they can
provide the needed sensitivity and are treated with the same corrective
techniques for spectral interference. (See 5.1.1.).

*The estimated instrumental detection limits as shown are taken from
“Inductively Coupled Plasma-Atomic Emission Spectroscopy-Prominent
Lines, “EPA-600/4-79-017. They are given as a guide for an instrumentak
limit. The actual method detection limits are sample dependent and may yary
as the sample matrix varies.

SHighly dependent on operating conditions and plasma position.

Dec. 1982 Metals-8


Foreword

Environmental measurements are required to determine the quality of

ambient waters and the character of waste effluents. The Environmental
Monitoring and Support Laboratory - Cincinnati, conducts research to

@ Develop and evaluate methods to measure the presence and concentration
of physical, chemical, and radiological pollutants in water, wastewater, bottom
sediments, and solid waste

@ Investigate methods for the concentration, recovery, and identification of
viruses, bacteria and other microbiological organisms in water; and, to
determine the responses of aquatic organisms to water quality.

@ Develop and operate an Agency-wide quality assurance program to assure
standardization and quality control of systems for monitoring water and
wastewater.

@ Develop and operate a computerized system for instrument automation
leading to improved data collection, analysis, and quality control

The preservation and holding times table and the six methods herein have been
added to Methods for Chemical Analysis of Water and Wastes, EPA 600/4-79-
020, as of the second printing, in an effort to provide updated analytical
information to laboratories complying with the Safe Drinking Water Act, the
National Pollutant Discharge Elimination System, Section 304(h) of the Clean
Water Act, and the Ambient Monitoring Requirements of Sections 106 and 208
of Public Law 92-500.

Roteck ZL. GorFG

Robert L. Booth, Acting Director
Environmental Monitoring and Support
Laboratory - Cincinnati

iii


7.2 Immerse pH electrode(s) into
sample and stir at a rate that does not
cause sample surface disturbance.

7.3 Titrate with 0.02 N NaOH (6.2)
to pH 8.3. Titration should be made as
quickly as possible to prevent
absorption of atmospheric COz.
Record volume of titrant.

8. Calculation

8.1 Acidity, weq/L ="8x Noa x 10°
mLs

ueg/L = microequivalents
per liter

mLe = mL of NaOH titrant
mLs = mL of sample
Ne = normality of titrant
9. Precision and Accuracy

9.1 Precision and accuracy data are
not available.

References

1. Seymour, M.D., Schubert, S.A.,
Clayton, J.W. and Fernando, Q.,
Variation in the Acid Content of
Rain Water in the Course of a
Single Precipitation, Water, Air
and Soil Pollution 10(2): 147-161,
Aug. 1978.

2. Peden, M.E. and Skowron, lonic
Stability of Precipitation Samples;
Atmospheric Environment, Vol
12, pp. 2343-2349. 1978.

3. USGS, Methods for Collection and
Analysis of Water Samples for
Dissolved Minerals and Gases, p.
39, (1970).

4. Annual Book of ASTM Standards,
part 31, “Water,” p. 107, D1067,
(1978).

5. Standard Methods for the
Examination of Water and
Wastewater, 14th Edition, p. 273,
Method 402 (1975).

Dec. 1982

308.2-2


Notice

This document has been reviewed in accordance with U.S. Environmental
Protection Agency policy and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.


and set the calibration within 25%
(8.5.4), reanalyze the system blank,
and then begin 8.5.1 again. If the
meter reading (see 9.1) is within 25%
of the calculated value, continue to
next step. The calculated value is
defined in 8.5.2

8.5.2 Calculate the factor for the
deviation of the instrument reading
(see 9.1) for the standard (7.4) from
the calculated value by:

standard reading -
Calculated value = FACTOR

calculated value

where the calculated value is that
value obtained by using the weight of
potassium hydrogen phthalate and
does not include the carbon
contributed by the reagent distilled
water (7.1) with which it has been
diluted.

8.5.3 Calculate the adjusted reading
by:

calculated value + (RDW - (FACTOR X
RDW)) = ADJUSTED READING

where RDW = mean reagent distilled
water (7.1) value.

8.5.4 Push in CALIBRATE button
after READY light comes on and
adjust the SPAN control to the
ADJUSTED READING calculated in
8.5.3.

8.6 Analyze the standards 7.3 and 7.5
in order to check the linearity of the
instrument at least once each day:

Transfer 10 mL of the solution-with-
reagent to the first sparger and start
analyzer cycle

ignore the meter reading for the first
cycle

Transfer a second 10 mL of the
solution-with-reagent to the first
sparger and start the analyzer cycle

Record the meter reading (see 9.1) of
the final carbon value for each of the
standards 7.3 and 7.5.

The range of concentration used for
calibrating the instrument and
checking the linearity of the
instrument should be ascertained
from a knowledge of the range of
concentrations expected from the
samples. Standards for lower ranges
can be prepared by diluting standards
7.2, 7.3, and 7.4

8.7 Analyze the samples. Transfer
10 mL of sample with reagent to the
first sparger and start the analysis
cycle.

+ US. GOVERNMENT PRINTING OFFICE: 880-659-095 /0559

Transfer 10 mL of the solution-with-
reagent to the first sparger and start
analyzer cycle

Ignore the meter reading for the first
cycle

Transfer a second 10 mL of the
solution-with-reagent to the first
sparger and start the analyzer cycle

Record the meter reading (see 9.1) of
the final carbon value for each of the
samples.

9. Calculations

9.1 The values are read off the final
digital readout in pg/L. The system
blank reading obtained in 8.2 must be
subtracted from all reagent distilled
water, standard and sample readings.

10. Precision and Accuracy

10.1 In a single laboratory (MERL),
using raw river water, centrifuged
river water, drinking water, and the
effluent from a carbon column which
had concentrations of 3.11, 3.10,
1.79, and 0.07 mg/L total organic
carbon respectively, the standard
deviations from ten replicates were
+0.13, +0.03, +0.02, and +0.02
mg/L, respectively.

10.2 Ina single laboratory (MERL),
using potassium hydrogen phthalate
in distilled water at concentrations of
5.0 and 1.0 mg/L total organic carbon,
recoveries were 80% and 91%,
respectively,

Bibliography

1. Proposed Standard Method for
Purgeable and Nonpurgeable Organic
Carbon in Water (UV-promoted,
persulfate oxidation method). ASTM
Committee D-19, Task Group
19.06.02.03 (Chairman R. J. Joyce),
January 1978.

2. Operating Instruction Dohrmann
Envirotech, 3420 Scott Boulevard,
Santa Clara, California 95050.

3. Takahashi, Y., “Ultra Low Level
TOC Analysis of Potable Waters.”
Presented at Water Quality
Technology Conference, AWWA, Dec.
5-8, 1976.

415.2-3 Dec. 1982


7.3.3 Arsenic solution, stock, 1 mL =
100 yg As: Dissolve 0.1320 g of As203
in 100 mL of deionized, distilled water
containing 0.4 g NaOH. Acidify the
solution with 2 mL conc. HNO3 and
dilute to 1,000 mL with deionized,
distilled water,

7.3.4 Barium solution, stock, 1 mL
= 100 ug Ba: Dissolve 0.1516 g BaClz
(dried at 250°C for 2 hrs) in 10 mL
deionized, distilled water with 1 mL
(1+1) HCL. Add 10.0 mL (1+1) HCI

and dilute to 1,000 mL with deionized,
distilled water.

7.3.5 Beryllium solution, stock, 1
mL = 100 pg Be: Do not dry. Dis-
solve 1.966 g BeSOs-4 4H20, in
deionized, distilled water, add 10.0 mL
conc. HNOs and dilute to 1,000 mL
with deionized, distilled water,

7.3.6 Boron solution, stock, 1 mL

= 100 yg B: Do not dry. Dissolve
0.5716 g anhydrous HaBOs in deionized
distilled water dilute to 1,000 mL.

Use a reagent meeting ACS specifica-
tions, keep the bottle tightly stoppered
and store in a desiccator to prevent
the entrance of atmospheric moisture.

7.3.7 Cadmium solution, stock, 1
mL = 100 yg Cd: Dissolve 0.1142 g
CdO in a minimum amount of (1+1)
HNOs. Heat to increase rate of dis-
solution. Add 10.0 mL conc. HNO3
and dilute to 1,000 mL with deionized,
distilled water,

7.3.8 Calcium solution, stock, 1 mL.
= 100 yg Ca: Suspend 0.2498 g
CaCOs dried at 180°C for 1 h before
weighing in deionized, distilled water
and dissolve cautiously with a min-
imum amount of (1+1) HNOs. Add
10.0 mL cone HNOs and dilute to
1,000 mL with deionized, distilled
water

7.3.9 Chromium solution, stock, 1
mL = 100 yg Cr: Dissolve 0.1923

g of CrOs in deionized, distilled
water. When solution is complete,
acidify with 10 mL conc. HNO; and
dilute to 1,000 mL with deionized,
distilled water.

7.3.10 Cobalt solution, stock, 1

mL = 100 yg Co: Dissolve 0.1000 g

of cobalt metal in a minimum amount
of (1+1) HNOs. Add 10.0 mL (1+1) HCI
and dilute to 1,000 mL with deionized,
distilled water

7.3.11 Copper solution, stock, 1
mL = 100 yg Cu: Dissolve 0.1252 g
CuO in a minimum amount of (1+1)
HNOs, Add 10.0 mL conc. HNOs and
dilute to 1,000 mL with deionized,
distilled water

7.3.12 Iron solution, stock, 1 mL
= 100 yg Fe: Dissolve 0.1430 g
Fe2O3 in a warm mixture of 20 mL
(1+1) HCI and 2 mL of conc. HNOs.
Cool, add an additional 5 mL of conc.
HNO; and dilute to 1000 mL with
deionized, distilled water

7.3.13 Lead solution, stock, 1 mL

= 100 yg Pb: Dissolve 0.1599 g
Pb(NO3}> in minimum amount of

(1#1) HNO. Add 10.0 mL conc. HNO3
and dilute to 1,000 mL with deionized,
distilled water.

7.3.14 Magnesium solution, stock, 1
mL = 100 yg Mg: Dissolve 0.1658 g
MgO in a minimum amount of (1+1)
HNOs. Add 10.0 mL conc. HNO; and
dilute to 1,000 mL with deionized,
distilled water.

7.3.15 Manganese solution, stock, 1
mL = 100 yg Mn: Dissolve 0.1000 g
of manganese metal in the acid mix-
ture 10 mL conc. HCI and 1 mL cone.
HNOs, and dilute to 1,000 mL with
deionized, distilled water.

7.3.16 Molybdenum solution, stock,
1 mL = 100 yg Mo: Dissolve 0.2043 g
(NHa}2MoO, in deionized, distilled
water and dilute to 1,000 mL.

7.3.17 Nickel solution, stock, 1
mL = 100 yg Ni: Dissolve 0.1000 g
of nickel metal in 10 mL hot conc.
HNOs, cool and dilute to 1,000 mL
with deionized, distilled water.

7.3.18 Potassium solution, stock, 1
mL = 100 yg K: Dissolve 0.1907 g
KCI, dried at 110°C, in deionized,
distitled water dilute to 1,000 mL.

7.3.19 Selenium solution, stock, 1
mL = 100 ug Se: Do not dry. Dissolve
0.1727 g H2Se0s (actual assay 94.6%)
in deionized, distilled water and dilute
to 1,000 mL.

7.3.20 Silica solution, stock, 1 mL
= 100 yg SiOz: Do not dry. Dissolve
0.4730 g NazSiOs - 9H20 in deionized,
distilled water. Add 10.0 mL conc.
HNOs and dilute to 1,000 mL with
deionized, distilled water

7.3.21 Silver solution, stock, 1
mL = 100 zg Ag: Dissolve 0.1575 g
AgNOz in 100 mL of deionized, dis-
tilled water and 10 mL conc. HNOs.
Dilute to 1,000 mL with deionized,
distilled water,

7.3.22 Sodium solution, stock, 1
mL = 100 yg Na: Dissolve 0.2542 g
NaC! in deionized, distilled water
Add 10.0 mL conc. HNOs and dilute
to 1,000 mL with deionized, distilled
water.

Dec. 1982 Metals-4

7.3.23 Thallium solution, stock, 1
mL = 100 yg TI: Dissolve 0.1303 g
TINOs in deionized, distilled water
Add 10.0 mL conc. HNOs and dilute
to 1,000 mL with deionized, distilled
water

7.3.24 Vanadium solution, stock, 1
mL = 100 yg V: Dissolve 0.2297
NH4VOz in a minimum amount of
conc. HNOs. Heat to increase rate
of dissolution. Add 10.0 mL conc.
HNOsz and dilute to 1,000 mL. with
deionized, distilled water.

7.3.25 Zinc solution, stock, 1 mL

= 100 yg Zn: Dissolve 0.1245 g ZnO
in a minimum amount of dilute HNOs.
Add 10.0 mL conc. HNO; and dilute
to 1,000 mL with deionized, distilled
water.

7.4 Mixed calibration standard so-
/utions—Prepare mixed calibration
standard solutions by combining ap-
propriate volumes of the stock solu-
tions in volumetric flasks. (See 7.4.1
thru 7.4.5) Add 2 mL of (1+1)

HCI and dilute to 100 mL with
deionized, distilled water. (See Notes
1 and 6.) Prior to preparing the mixed
standards, each stock solution should
be analyzed separately to determine
possible spectral interference or the
presence of impurities. Care should
be taken when preparing the mixed
standards that the elements are com-
patible and stable. Transfer the mixed
standard solutions to a FEP fluoro-
carbon or unused polyethylene bottle
for storage. Fresh mixed standards
should be prepared as needed with
the realization that concentration can
change on aging. Calibration stand-
ards must be initially verified using

a quality control sample and moni-
tored weekly for stability (See 7.6.3).
Although not specifically required,
some typical calibration standard com-
binations follow when using those
specific wavelengths listed in Table

1

7.4.1 Mixed standard solution |—
Manganese, beryllium, cadmium, lead,
and zinc.

7.4.2. Mixed standard solution I!—
Barium, copper, iron, vanadium, and
cobalt.

7.4.3 Mixed standard solution fl
Molybdenum, silica, arsenic, and
selenium.

7.4.4 Mixed standard solution IV—
Calcium, sodium, potassium, alumi-
num, chromium and nickel


3. The interference effect must be
constant over the working range of
concern.

4. The signal must be corrected for
any additive interference

11. Calculation

11.1 Reagent blanks (7.5.2) should
be subtracted from all samples. This is
particularly important for digested
samples requiring large quantities of
acids to complete the digestion.

11.2 If dilutions were performed,
the appropriate factor must be applied
to sample values.

11.3 Data should be rounded to the
thousandth place and all results
should be reported in mg/L up to
three significant figures.

12. Quality Control
(Instrumental)

12.1 Check the instrument
standardization by analyzing
appropriate quality control check
standards as follow:

12.1.1 Analyze an appropriate
instrument check standard (7.6.1)
containing the elements of interest at
a frequency of 10%. This check
standard is used to determine
instrument drift. If agreement is not
within +5% of the expected values or
within the established control limits,
whichever is lower, the analysis is out
of control. The analysis should be
terminated, the problem corrected,
and the instrument recalibrated.

Analyze the calibration blank (7.5.1)
at a frequency of 10%. The result
should be within the established
control limits of two standard devia-
tions of the mean value. If not, repeat
the analysis two more times and
average the three results. If the
average is not within the control limit,
terminate the analysis, correct the
problem and recalibrate the
instrument.

12.1.2 To verify interelement and
background correction factors analyze
the interference check sample (7.6.2)
at the beginning, end, and at periodic
intervals throughout the sample run.
Results should fall within the
established control limits of 1.5 times
the standard deviation of the mean
value. If not, terminate the analysis,
correct the problem and recalibrate
the instrument.

12.1.3 A quality control sample
(7.6.3) obtained from an outside
source must first be used for the
initial verification of the calibration

standards. A fresh dilution of this
sample shall be anlayzed every week
thereafter to monitor their stability. If
the results are not within +5% of the
true value listed for the control
sample, prepare a new calibration
standard and recalibrate the
instrument. If this does not correct the
problem, prepare a new stock
standard and a new calibration
standard and repeat the calibration

Precision and Accuracy

13.1 In an EPA round robin phase 1
study, seven laboratories applied the
ICP technique to acid-distilled water
matrices that had been dosed with
various metal concentrates. Table 4
lists the true value, the mean reported
value and the mean % relative
standard deviation.

References

1. Winge, R.K., V.J. Peterson, and
VA. Fassel, “Inductively Coupled
Plasma-Atomic Emission
Spectroscopy: Prominent Lines,”’ EPA-
600/4-79-017.

2. Winefordner, J.D., “Trace
Analysis: Spectroscopic Methods for
Elements,’ Chemical Analysis, Vol.
46, pp. 41-42

3. Handbook for Analytical Quality
Control in Water and Wastewater
Laboratories, EPA-600/4-79-019.

4. Garbarino, J.R. and Taylor, H.E.,
“An Inductively-Coupled Plasma
Atomic Emission Spectrometric
Method for Routine Water Quality
Testing,’’ Applied Spectroscopy 33,
No. 3(1979).

5. “Methods for Chemical Analysis of
Water and Wastes,” EPA-600/4-79-
020.

6. Annual Book of ASTM Standards,
Part 31.

7. “Carcinogens - Working With
Carcinogens,”’ Department of Health,
Education, and Welfare, Public Health
Service, Center for Disease Control,
National Institute for Occupational
Safety and Health, Publication No. 77-
206, Aug. 1977.

8. “OSHA Safety and Health Stan-
dards, General Industry,” (29 CFR
1910), Occupational Safety and Health
Administration, OSHA 2206, (Revised,
January 1976).

9. “Safety in Academic Chemistry
Laboratories, American Chemical So-
ciety Publication, Committee on
Chemical Safety, 3rd Edition, 1979.

Metals-7 Dec. 1982