EPA-821-R-01-010
January 2001
METHOD 200.7
TRACE ELEMENTS IN WATER, SOLIDS, AND BIOSOLIDS
BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION
SPECTROMETRY
Revision 5.0
January 2001
U.S. Environmental Protection Agency
Office of Science and Technology
Ariel Rios Building
1200 Pennsylvania Avenue, N.W.
Washington, D.C. 20460
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Method 200.7
Acknowledgments
Revision 5.0 of Method 200.7 was prepared under the direction of William A. Telliard of the U.S.
Environmental Protection Agency's (EPA's) Office of Water (OW), Engineering and Analysis Division
(EAD) in collaboration with Ted Martin, of EPA's Office of Research and Development's National
Exposure Research Laboratory in Cincinnati, Ohio. The method was prepared under EPA Contract 68-
C3-0337 and 68-C-98-139 by DynCorp I&ET with assistance from Quality Works, Inc. and Westover
Scientific, Inc.
The following personnel at the EPA Office of Research and Development's National Exposure Research
Laboratory in Cincinnati, Ohio, are gratefully acknowledged for the development of the analytical
procedures described in this method:
USEPA-ICP Users Group (Edited by T.D. Martin and J.F. Kopp) - Method 200.7, Revision 1.0, (Printed
1979, Published 1982)
T.D. Martin and E.R. Martin - Method 200.7, Revision 3.0 (1990)
T.D. Martin, C.A. Brockhoff, J.T. Creed, and S.E. Long (Technology Applications Inc.) - Method 200.7,
Revision 3.3 (1991)
T.D. Martin, C.A. Brockhoff, J.T. Creed, and EMMC Methods Work Group - Method 200.7, Revision 4.4
(1994)
Disclaimer
This draft method has been reviewed and approved for publication by the Analytical Methods Staff within
the Engineering and Analysis Division of the U.S. Environmental Protection Agency. Mention of trade
names or commercial products does not constitute endorsement or recommendation for use. EPA plans
further validation of this draft method. The method may be revised following validation to reflect results of
the study. This method version contains minor editorial changes to the October 2000 version.
EPA welcomes suggestions for improvement of this method. Suggestions and questions concerning this
method or its application should be addressed to:
W.A. Telliard
Analytical Methods Staff (4303)
Office of Science and Technology
U.S. Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Avenue, N.W.
Washington, D.C. 20460
Phone: 202/260-7134
Fax: 202/260-7185
Draft January 2001
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Method 200.7
Note: This method is performance based. The laboratory is permitted to omit any step or modify any
procedure provided that all performance requirements in this method are met. The laboratory may not
omit any quality control analyses. The terms "shall," "must," and "may not" define procedures required
for producing reliable results. The terms "should" and "may" indicate optional steps that may be
modified or omitted if the laboratory can demonstrate that the modified method produces results
equivalent or superior to results produced by this method.
January 2001 Draft
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Method 200.7
Trace Elements in Water, Solids, and Biosolids by
Inductively Coupled Plasma-Atomic Emission Spectrometry
1.0 Scope and Application
1.1 Inductively coupled plasma-atomic emission spectrometry (ICP-AES) is used to
determine metals and some nonmetals in solution. This method is a
consolidation of existing methods for water, wastewater, and solid wastes
(References 1-4). For analysis of petroleum products see References 5 and 6.
This method is applicable to the following analytes:
Analyte
Chemical Abstract Services
Registry Number (CASRN)
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Cerium3
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silicab
Silver
(Al)
(Sb)
(As)
(Ba)
(Be)
(B)
(Cd)
(Ca)
(Ce)
(Cr)
(Co)
(Cu)
(Fe)
(Pb)
(Li)
(Mg)
(Mn)
(Hg)
(Mo)
(Ni)
(P)
(K)
(Se)
(Si02)
(Ag)
7429-90-5
7440-36-0
7440-38-2
7440-39-3
7440-41-7
7440-42-8
7440-43-9
7440-70-2
7440-45-1
7440-47-3
7440-48-4
7440-50-8
7439-89-6
7439-92-1
7439-93-2
7439-95-4
7439-96-5
7439-97-6
7439-98-7
7440-02-0
7723-14-0
7440-09-7
7782-49-2
7631-86-9
7440-22-4
January 2001
Draft
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Method 200.7
Chemical Abstract Services
Analyte Registry Number (CASRN)
Sodium
Strontium
Thallium
Tin
Titanium
Vanadium
Yttrium
Zinc
(Na)
(Sr)
(Tl)
(Sn)
(Ti)
(V)
(Y)
(Zn)
7440-23-5
7440-24-6
7440-28-0
7440-31-5
7440-32-6
7440-62-2
7440-65-5
7440-66-6
aCerium has been included as a method analyte for correction of potential
inter-element spectral interference.
bThis method is not suitable for the determination of silica in solids.
1.2 To confirm approval of this method for use in compliance monitoring programs
[e.g., Clean Water Act (NPDES) or Safe Drinking Water Act (SDWA)] consult
both the appropriate sections of the Code of Federal Regulation (40 CFR Part
136 Table 1B for NPDES, and Part 141 § 141.23 for drinking water) and the
latest Federal Register announcements.
1.3 ICP-AES can be used to determine dissolved analytes in aqueous samples after
suitable filtration and acid preservation. To reduce potential interferences,
dissolved solids should be <0.2% (w/v) (Section 4.2).
1.4 With the exception of silver, where this method is approved for the determination
of certain metal and metalloid contaminants in drinking water, aqueous samples
may be analyzed directly by pneumatic nebulization without acid digestion if the
sample has been properly preserved with acid and has turbidity of <1 NTU at the
time of analysis. This total recoverable determination procedure is referred to as
"direct analysis." However, in the determination of some primary drinking water
metal contaminants, preconcentration of the sample may be required prior to
analysis in order to meet drinking water acceptance performance criteria
(Sections 11.2.2 through 11.2.7).
1.5 For the determination of total recoverable analytes in aqueous, biosolids
(municipal sewage sludge), and solid samples, a digestion/extraction is required
prior to analysis when the elements are not in solution (e.g., soil, sludge,
sediment, and aqueous samples that may contain particulate and suspended
solids). Aqueous samples containing total suspended solids>1% (w/v) should
be extracted as a solid type sample.
Draft January 2001
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Method 200.7
1.6 When determining boron and silica in aqueous samples, only plastic, PTFE or
quartz labware should be used from time of sample collection to completion of
analysis. For accurate determination of boron in solid and sludge samples, only
quartz or PTFE beakers should be used during acid extraction with immediate
transfer of an extract aliquot to a plastic centrifuge tube following dilution of the
extract to volume. When possible, borosilicate glass should be avoided to
prevent contamination of these analytes.
1.7 Silver is only slightly soluble in the presence of chloride unless there is a
sufficient chloride concentration to form the soluble chloride complex.
Therefore, low recoveries of silver may occur in samples, fortified sample
matrices and even fortified blanks if determined as a dissolved analyte or by
"direct analysis" where the sample has not been processed using the total
recoverable mixed acid digestion. For this reason it is recommended that
samples be digested prior to the determination of silver. The total recoverable
sample digestion procedure given in this method is suitable for the determination
of silver in aqueous samples containing concentrations up to 0.1 mg/L. For the
analysis of wastewater samples containing higher concentrations of silver,
succeeding smaller volume, well-mixed aliquots should be prepared until the
analysis solution contains <0.1 mg/L silver. The extraction of solid or sludge
samples containing concentrations of silver >50 mg/kg should be treated in a
similar manner.
NOTE: When analyzing samples containing high levels of silver as might occur in the
photographic manufacturing industries, EPA Method 272.1 can be used for silver
determinations. Based on the use of cyanogen iodide (CNI) as a stabilizing agent, Method 272.1
can be used on samples containing up to 4 mg/L ofAg. However, it should be recognized that
CNI is an extremely hazardous and environmentally toxic reagent, and should be used with the
utmost caution.
1.8 The extraction of tin from solid or sludge samples should be prepared using
aliquots <1 g when determined sample concentrations exceed 1%.
1.9 The total recoverable sample digestion procedures given in this method will
solubilize and hold in solution only minimal concentrations of barium in the
presence of free sulfate. For the analysis of barium in samples having varying
and unknown concentrations of sulfate, analysis should be completed as soon
as possible after sample preparation.
1.10 The total recoverable sample digestion procedure given in this method is not
suitable for the determination of volatile organo-mercury compounds. However,
if digestion is not required (turbidity <1 NTU), the combined concentrations of
inorganic and organo-mercury in solution can be determined by "direct analysis"
pneumatic nebulization provided the sample solution is adjusted to contain the
January 2001 Draft
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Method 200.7
same mixed acid (HN03 + HCI) matrix as the total recoverable calibration
standards and blank solutions.
1.11 This method will be validated in biosolids for those analytes regulated under 40 CFR Part
503 only. It is believed to be applicable for the analysis of biosolids for all analytes listed
in Section 1.1. There may be difficulties in analyzing molybdenum in biosolids with a
radial TCP, thus the determination of some analytes in biosolids may require the use of an
axial TCP. More information will be provided by the validation study.
1.12 Detection limits and linear ranges for the elements will vary with the wavelength
selected, the spectrometer, and the matrices. Method detection limits (MDLs; 40
CFR 136, appendix B) and minimum levels (MLs) when no interferences are
present will be determined for this method through a validation study.
Preliminary MDL values are given in Table 4. The ML for each analyte can be
calculated by multiplying the MDL by 3.18 and rounding to the nearest (2, 5, or
10X10") where n is an integer.
1.13 Users of the method data should state the data-quality objectives prior to
analysis. Users of the method must document and have on file the required
initial demonstration performance data described in Section 9.2 prior to using
the method for analysis.
2.0 Summary of Method
2.1 An aliquot of a well-mixed, homogeneous sample is accurately weighed or
measured for sample processing. For total recoverable analysis of a solid or an
aqueous sample containing undissolved material, analytes are solubilized by
gentle refluxing with HN03 and HCI. For the total recoverable analysis of a
sludge sample containing <1% total suspended solids, analytes are solubilized
by successive refluxing with HN03 and HCI. For total recoverable analysis of a
sludge sample containing total suspended solids >1% (w/v), analytes are
solubilized by refluxing with HN03, background organic materials are oxidized
with peroxide, and analytes are further solubilized by refluxing with HCI. After
cooling, the sample is made up to volume, mixed and then centrifuged or
allowed to settle overnight prior to analysis. For the determination of dissolved
analytes in a filtered aqueous sample aliquot, or for the "direct analysis" total
recoverable determination of analytes in drinking water where sample turbidity is
<1 NTU, the sample is made ready for analysis by the addition of the appropriate
volume of HN03, and then diluted to a predetermined volume and mixed before
analysis.
2.2 The analysis described in this method involves multi-elemental determinations
by ICP-AES using sequential or simultaneous instruments. The instruments
measure characteristic atomic-line emission spectra by optical spectrometry.
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Method 200.7
Samples are nebulized and the resulting aerosols are transported to the plasma
torch. Element specific emission spectra are produced by a radio-frequency
inductively coupled plasma. The spectra are dispersed by a grating
spectrometer, and the intensities of the line spectra are monitored at specific
wavelengths by a photosensitive device. Photocurrents from the photosensitive
device are processed and controlled by a computer system. A background
correction technique is required to compensate for variable background
contribution to the determination of the analytes. The background must be
measured adjacent to an analyte wavelength during analysis. Interferences
must be considered and addressed appropriately as discussed in Sections 4.0,
7.0, 9.0, and 11.0.
3.0 Definitions
3.1 Biosolids-A solid, semisolid, or liquid residue (sludge) generated during
treatment of domestic sewage in a treatment works.
3.2 Calibration blank-A volume of reagent water acidified with the same acid matrix
as the calibration standards (Section 7.12.1). The calibration blank is a zero
standard and is used to calibrate the ICP instrument.
3.3 Calibration standard-A solution prepared from the dilution of stock standard
solutions (Section 7.11). The calibration solutions are used to calibrate the
instrument response with respect to analyte concentration.
3.4 Calibration verification (CV) solution-A solution of method analytes, used to
evaluate the performance of the instrument system with respect to a defined set
of method criteria (Section 7.13).
3.5 Dissolved analvte-The concentration of analyte in an aqueous sample that will
pass through a 0.45 urn membrane filter assembly prior to sample acidification
(Section 8.2).
3.6 Field blank-An aliquot of reagent water or other blank matrix that is placed in a
sample container in the laboratory and treated as a sample in all respects,
including shipment to the sampling site, exposure to the sampling site
conditions, storage, preservation, and all analytical procedures (Section 8.5).
The field blank is analyzed to determine if method analytes or other
interferences are present in the field environment.
3.7 Internal standard-Pure analyte(s) added to a sample, extract, or standard
solution in a known amount(s) and used to measure the relative responses of
other method analytes that are components of the same sample or solution. The
internal standard must be an analyte that is not a sample component
(Section 11.6).
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Method 200.7
3.8 Linear dynamic range (LDR)-The concentration range over which the instrument
response to an analyte is linear (Section 9.2.3).
3.9 Matrix spike (MS) and matrix spike duplicate (MSD)-Two aliquots of the same
environmental sample to which known quantities of the method analytes are
added in the laboratory. The MS and MSD are analyzed exactly like a sample,
and their purpose is: to determine whether the sample matrix contributes bias to
the analytical results, and to indicate precision associated with laboratory
procedures. The background concentrations of the analytes in the sample
matrix must be determined in a separate aliquot and the measured values in the
MS and MSD corrected for background concentrations (Section 9.5).
3.10 Mav-This action, activity, or procedural step is neither required nor prohibited.
3.11 May not-This action, activity, or procedural step is prohibited.
3.12 Method blank-An aliquot of reagent water or other blank matrix that is treated
exactly as a sample including exposure to all glassware, equipment, solvents,
reagents, and internal standards that are used with other samples. The method
blank is used to determine if method analytes or other interferences are present
in the laboratory environment, reagents, or apparatus (Section 7.12.2).
3.13 Method detection limit (MDL)-The minimum concentration of an analyte that can
be identified, measured, and reported with 99% confidence (Section 9.2.1). The
MDL is determined according to procedures described in 40 CFR Part 136,
Appendix B.
3.14 Minimum level (ML)-The lowest level at which the entire analytical system gives
a recognizable signal and acceptable calibration point for the analyte. It is
equivalent to the concentration of the lowest calibration standard, assuming that
all method-specific sample weights, volumes and cleanup procedures have been
employed.
3.15 Must-This action, activity, or procedural step is required.
3.16 Ongoing precision and recovery standard (OPR)-The OPR test is used to
ensure that the laboratory meets performance criteria during the period that
samples are analyzed. It also separates laboratory performance from method
performance on the sample matrix. For aqueous samples, the OPR solution is
an aliquot of method blank to which known quantities of the method analytes are
added in the laboratory. For solid samples, the use of clean sand, soil or peat
moss to which known quantities of the method analytes are added in the
laboratory is recommended. The OPR is analyzed in the same manner as
samples (Section 9.7).
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Method 200.7
3.17 Plasma solution-A solution that is used to determine the optimum height above
the work coil for viewing the plasma (Section 7.16).
3.18 Reference sample-A solution of method analytes of known concentrations which
is used to fortify an aliquot of method blank or sample matrix (Section 7.14). The
reference sample is obtained from a source external to the laboratory and
different from the source of calibration standards. It is used to check laboratory
and/or instrument performance.
3.19 Shall-This action, activity or procedural step is required.
3.20 Should-This action, activity, or procedural step is suggested but not required.
3.21 Solid sample-For the purpose of this method, a sample taken from material
classified as either soil, sediment or industrial sludge.
3.22 Spectral interference check (SIC) solution-A solution of selected method
analytes of higher concentrations which is used to evaluate the procedural
routine for correcting known inter-element spectral interferences with respect to
a defined set of method criteria (Sections 7.15 and 9.4).
3.23 Standard addition-The addition of a known amount of analyte to the sample in
order to determine the relative response of the detector to an analyte within the
sample matrix. The relative response is then used to assess either an operative
matrix effect or the sample analyte concentration (Sections 9.5.3.1 and 11.6).
3.24 Standard stock solution-A concentrated solution containing one or more method
analytes prepared in the laboratory using assayed reference materials or
purchased from a reputable commercial source (Section 7.10).
3.25 Total recoverable analvte-The concentration of analyte determined either by
"direct analysis" of an unfiltered acid preserved drinking water sample with
turbidity of <1 NTU (Section 11.2.1), or by analysis of the solution extract of a
sludge, solid, or unfiltered aqueous sample following digestion by refluxing with
hot dilute mineral acid(s) as specified in the method (Sections 11.2 through
11.4).
3.26 Total Solids-The residue left in the vessel after evaporation of liquid from a
sample and subsequent drying in an oven at 103°C to 105°C.
3.27 Water sample-For the purpose of this method, a sample taken from one of the
following sources: drinking, surface, ground, storm runoff, industrial or domestic
wastewater.
January 2001 Draft
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Method 200.7
4.0 Interferences
4.1 Spectral interferences are caused by background emission from continuous or
recombination phenomena, stray light from the line emission of high
concentration elements, overlap of a spectral line from another element, or
unresolved overlap of molecular band spectra.
4.1.1 Background emission and stray light can usually be compensated for by
subtracting the background emission determined by measurement(s)
adjacent to the analyte wavelength peak. Spectral scans of samples or
single element solutions in the analyte regions may indicate not only
when alternate wavelengths are desirable because of severe spectral
interference, but also will show whether the most appropriate estimate of
the background emission is provided by an interpolation from
measurements on both sides of the wavelength peak or by the measured
emission on one side or the other. The location(s) selected for the
measurement of background intensity will be determined by the
complexity of the spectrum adjacent to the wavelength peak. The
location(s) used for routine measurement must be free of off-line spectral
interference (inter-element or molecular) or adequately corrected to
reflect the same change in background intensity as occurs at the
wavelength peak.
4.1.2 Spectral overlaps may be avoided by using an alternate wavelength or
can be compensated for by equations that correct for inter-element
contributions, which involves measuring the interfering elements. Some
potential on-line spectral interferences observed for the recommended
wavelengths are given in Table 2. When operative and uncorrected,
these interferences will produce false positive determinations and be
reported as analyte concentrations. The interferences listed are only
those that occur between method analytes. Only interferences of a direct
overlap nature that were observed with a single instrument having a
working resolution of 0.035 nm are listed. More extensive information on
interferant effects at various wavelengths and resolutions is available in
Boumans' Tables (Reference 8). Users may apply inter-element
correction factors determined on their instruments within tested
concentration ranges to compensate (off-line or on-line) for the effects of
interfering elements.
4.1.3 When inter-element corrections are applied, there is a need to verify their
accuracy by analyzing spectral interference check solutions as described
in Section 7.15. Inter-element corrections will vary for the same emission
line among instruments because of differences in resolution, as
determined by the grating plus the entrance and exit slit widths, and by
the order of dispersion. Inter-element corrections will also vary
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Method 200.7
depending upon the choice of background correction points. Selecting a
background correction point where an interfering emission line may
appear should be avoided when practical. Inter-element corrections that
constitute a major portion of an emission signal may not yield accurate
data. Users should not forget that some samples may contain uncommon
elements that could contribute spectral interferences (References 7 and
8).
4.1.4 The interference effects must be evaluated for each individual instrument
whether configured as a sequential or simultaneous instrument. For each
instrument, intensities will vary not only with optical resolution but also
with operating conditions (such as power, viewing height and argon flow
rate). When using the recommended wavelengths given in Table 1, the
analyst is required to determine and document for each wavelength the
effect from the known interferences given in Table 2, and to use a
computer routine for their automatic correction on all analyses. To
determine the appropriate location for off-line background correction, the
user must scan the area on either side adjacent to the wavelength and
record the apparent emission intensity from all other method analytes.
This spectral information must be documented and kept on file. The
location selected for background correction must either be free of off-line
inter-element spectral interference or a computer routine must be used for
automatic correction on all determinations. If a wavelength other than the
recommended wavelength is used, the user must determine and
document both the on-line and off-line spectral interference effect from all
method analytes and provide for automatic correction on all analyses.
Tests to determine the spectral interference must be done using analyte
concentrations that will adequately describe the interference. Normally,
100 mg/L single element solutions are sufficient, however, for analytes
such as iron that may be found at high concentration a more appropriate
test would be to use a concentration near the upper LDR limit. See
Section 9.4 for required spectral interference test criteria.
4.1.5 When inter-element corrections are not used, either ongoing SIC
solutions (Section 7.15) must be analyzed to verify the absence of inter-
element spectral interference, or a computer software routine must be
employed for comparing the determinative data to limits files for notifying
the analyst when an interfering element is detected in the sample at a
concentration that will produce either an apparent false positive
concentration greater than the analyte MDL, or false negative analyte
concentration less than the 99% lower control limit of the calibration
blank. When the interference accounts for 10% or more of the analyte
concentration, either an alternate wavelength free of interference or
another approved test procedure must be used to complete the analysis.
For example, the copper peak at 213.853 nm could be mistaken for the
January 2001 Draft ~9
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Method 200.7
zinc peak at 213.856 nm in solutions with high copper and low zinc
concentrations. For this example, a spectral scan in the 213.8 nm region
would not reveal the misidentification because a single peak near the zinc
location would be observed. The possibility of misidentification of copper
for the zinc peak at 213.856 nm can be identified by measuring the
copper at another emission line, e.g., 324.754 nm. Users should be
aware that, depending upon the instrumental resolution, alternate
wavelengths with adequate sensitivity and freedom from interference may
not be available for all matrices. In these circumstances the analyte must
be determined using another approved test procedure.
4.2 Physical interferences are effects associated with the sample nebulization and
transport processes. Changes in viscosity and surface tension can cause
significant inaccuracies, especially in samples containing high dissolved solids
or high acid concentrations. If physical interferences are present, they must be
reduced by such means as a high-solids nebulizer, diluting the sample, using a
peristaltic pump, or using an appropriate internal standard element. Another
problem that can occur with high dissolved solids is salt buildup at the tip of the
nebulizer, which affects aerosol flow rate and causes instrumental drift. This
problem can be controlled by a high-solids nebulizer, wetting the argon prior to
nebulization, using a tip washer, or diluting the sample. Also, it has been
reported that better control of the argon flow rates, especially for the nebulizer,
improves instrument stability and precision; this is accomplished with the use of
mass flow controllers.
4.3 Chemical interferences include molecular-compound formation, ionization
effects, and solute-vaporization effects. Normally, these effects are not
significant with the ICP-AES technique. If observed, they can be minimized by
careful selection of operating conditions (such as incident power and
observation height), by buffering of the sample, by matrix matching, and by
standard-addition procedures. Chemical interferences are highly dependent on
matrix type and the specific analyte element.
4.4 Memory interferences result when analytes in a previous sample contribute to
the signals measured in a new sample. Memory effects can result from sample
deposition on the uptake tubing to the nebulizer, and from the buildup of sample
material in the plasma torch and spray chamber. The site where these effects
occur is dependent on the element and can be minimized by flushing the system
with a rinse blank between samples (Section 7.12.1). The possibility of memory
interferences should be recognized within an analytical run and suitable rinse
times should be used to reduce them. The rinse times necessary for a particular
element must be estimated prior to analysis. This may be achieved by
aspirating a standard containing elements corresponding to either their LDR or a
concentration ten times those usually encountered. The aspiration time should
be the same as a normal sample analysis period, followed by analysis of the
10 Draft January 2001
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Method 200.7
rinse blank at designated intervals. The length of time required to reduce
analyte signals to within a factor of two of the method detection limit, should be
noted. Until the required rinse time is established, this method requires a rinse
period of at least 60 seconds between samples and standards. If a memory
interference is suspected, the sample must be analyzed again after a long rinse
period.
5.0 Safety
5.1 The toxicity or carcinogenicity of each reagent used in this method has not been
fully established. Each chemical should be regarded as a potential health
hazard and exposure to these compounds should be as low as reasonably
achievable. Each laboratory is responsible for maintaining a current awareness
file of OSHA regulations regarding the safe handling of the chemicals specified
in this method (References 9, 10, 11, and 12). A reference file of material data
handling sheets should also be made available to all personnel involved in the
chemical analysis. Specifically, concentrated HN03and HCI present various
hazards and are moderately toxic and extremely irritating to skin and mucus
membranes. Use these reagents in a fume hood whenever possible and if eye
or skin contact occurs, flush with large volumes of water. Always wear safety
glasses or a shield for eye protection, protective clothing, and observe proper
mixing when working with these reagents.
5.2 The acidification of samples containing reactive materials may result in the
release of toxic gases, such as cyanides or sulfides. Acidification and digestion
of samples should be done in a fume hood.
5.3 All personnel handling environmental samples known to contain or to have been
in contact with human waste should be immunized against known disease
causative agents.
5.4 The inductively coupled plasma should only be viewed with proper eye
protection from the ultraviolet emissions.
5.5 It is the responsibility of the user of this method to comply with relevant disposal
and waste regulations. For guidance, see Sections 14.0 and 15.0.
6.0 Equipment and Supplies
NOTE: The mention of trade names or commercial products in this method is for illustrative
purposes only and does not constitute endorsement or recommendation for use by the EPA.
Equivalent performance may be achievable using apparatus and materials other than those
suggested here. The laboratory is responsible for demonstrating equivalent performance.
January 2001 Draft 11
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Method 200.7
6.1 Inductively coupled plasma emission spectrometer:
6.1.1 Computer-controlled emission spectrometer with background-correction
capability. The spectrometer must be capable of meeting and complying
with the requirements described and referenced in Section 2.2.
6.1.2 Radio-frequency generator compliant with FCC regulations.
6.1.3 Argon gas supply-High purity grade (99.99%). When analyses are
conducted frequently, liquid argon is more economical and requires less
frequent replacement of tanks than compressed argon in conventional
cylinders.
6.1.4 A variable speed peristaltic pump is required to deliver both standard and
sample solutions to the nebulizer.
6.1.5 (Optional) Mass flow controllers to regulate the argon flow rates,
especially the aerosol transport gas, are highly recommended. Their use
will provide more exacting control of reproducible plasma conditions.
6.2 Analytical balance, with capability to measure to 0.1 mg, for use in weighing
solids, for preparing standards, and for determining dissolved solids in digests or
extracts.
6.3 A temperature adjustable hot plate capable of maintaining a temperature of
95°C.
6.4 (Optional) A temperature adjustable block digester capable of maintaining a
temperature of 95°C and equipped with 250-mL constricted digestion tubes.
6.5 (Optional) A steel cabinet centrifuge with guard bowl, electric timer and brake.
6.6 A gravity convection drying oven with thermostatic control capable of
maintaining 180°C±5°C.
6.7 (Optional) An air displacement pipetter capable of delivering volumes ranging
from 0.1-2500 uL with an assortment of high quality disposable pipet tips.
6.8 Mortar and pestle, ceramic or other nonmetallic material.
6.9 Polypropylene sieve, 5-mesh (4 mm opening).
6.10 Labware-Prevention of contamination and loss are of prime consideration for
determination of trace levels of elements. Potential contamination sources
12 Draft January 2001
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Method 200.7
include improperly cleaned laboratory apparatus and general contamination
within the laboratory environment from dust, etc. A clean laboratory work area
designated for trace element sample handling must be used. Sample containers
can introduce positive and negative errors in the determination of trace elements
by (1) contributing contaminants through surface desorption or leaching, and
(2) depleting element concentrations through adsorption processes. All
reusable labware (glass, quartz, polyethylene, PTFE, FEP, etc.) should be
sufficiently clean for the task objectives. One recommended procedure found to
provide clean labware includes washing with a detergent solution, rinsing with
tap water, soaking for four hours or more in 20% (v/v) HN03 or a mixture of
HN03 and HCI (1 +2+9), rinsing with reagent water and storing clean
(References 2 and 3). Chromic acid cleaning solutions must be avoided
because chromium is an analyte.
6.10.1 Glassware-Volumetric flasks, graduated cylinders, funnels and centrifuge
tubes (glass and/or metal-free plastic).
6.10.2 Assorted calibrated pipettes.
6.10.3 Conical Phillips beakers (Corning 1080-250 or equivalent), 250-mL with
50-mm watch glasses.
6.10.4 Griffin beakers, 250-mL with 75-mm watch glasses and (optional) 75-mm
ribbed watch glasses.
6.10.5 (Optional) PTFE and/or quartz Griffin beakers, 250-mL with PTFE covers.
6.10.6 Narrow-mouth storage bottles, FEP (fluorinated ethylene propylene) with
screw closure, 125-mL to 1-L capacities.
6.10.7 One-piece stem FEP wash bottle with screw closure, 125-mL capacity.
7.0 Reagents and Standards
7.1 Reagents may contain elemental impurities which might affect analytical data.
Only high purity reagents that conform to the American Chemical Society
specifications should be used whenever possible (Reference 13). If the purity of
a reagent is in question, analyze for contamination. All acids used for this
method must be of ultra-high purity grade or equivalent. Suitable acids are
available from a number of manufacturers. Redistilled acids prepared by sub-
boiling distillation are acceptable.
7.2 Hydrochloric acid, concentrated (specific gravity = 1.19).
January 2001 Draft 13
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Method 200.7
7.2.1 Hydrochloric acid (1+1 )-Add 500 ml concentrated HCI to 400 ml reagent
water and dilute to 1 L.
7.2.2 Hydrochloric acid (1+4)-Add 200 ml concentrated HCI to 400 ml reagent
water and dilute to 1 L.
7.2.3 Hydrochloric acid (1+20)-Add 10 ml concentrated HCI to 200 ml reagent
water.
7.3 Nitric acid, concentrated (specific gravity = 1.41).
7.3.1 Nitric acid (1 +1 )-Add 500 ml concentrated HN03 to 400 ml reagent
water and dilute to 1 L.
7.3.2 Nitric acid (1 +2)-Add 100 ml concentrated HN03 to 200 ml reagent
water.
7.3.3 Nitric acid (1 +5)-Add 50 ml concentrated HN03 to 250 ml reagent water.
7.3.4 Nitric acid (1 +9)-Add 10 ml concentrated HN03 to 90 ml reagent water.
7.4 Reagent water-All references to water in this method refer to ASTM Type I
grade water (Reference 14).
7.5 Ammonium hydroxide, concentrated (specific gravity = 0.902).
7.6 Tartaric acid-ACS reagent grade.
7.7 Hydrogen peroxide-H202.
7.7.1 Hydrogen peroxide, 50%, stabilized certified reagent grade.
7.7.2 Hydrogen peroxide, 30%, stabilized certified reagent grade.
7.8 Clean sand or soil-All references to clean sand or soil in this method refer to
sand or soil certified to be free of the analytes of interest at or above their MDLs
or to contain those analytes at certified levels.
7.9 Peat moss-All references to peat moss in this method refer to sphagnum peat
moss free of arsenic, cadmium, copper, lead, mercury, molybdenum, nickel,
selenium and zinc analytes at or above their MDLs (Table 4) or to contain those
analytes at certified levels.
14 Draft January 2001
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Method 200.7
7.10 Standard Stock Solutions-Stock standards may be purchased or prepared from
ultra-high purity grade chemicals (99.99-99.999% pure). All compounds must be
dried for one hour at 105°C, unless otherwise specified. It is recommended that
stock solutions be stored in FEP bottles. Replace stock standards when
succeeding dilutions for preparation of calibration standards cannot be verified.
CAUTION: Many of these chemicals are extremely toxic if inhaled or swallowed
(Section 5.1). Wash hands thoroughly after handling.
Typical stock solution preparation procedures follow for 1 L quantities
(Equations 1 and 2), but for the purpose of pollution prevention, the analyst is
encouraged to prepare smaller quantities when possible. Concentrations are
calculated based upon the weight of the pure element or upon the weight of the
compound multiplied by the fraction of the analyte in the compound.
Equation 1
From pure element,
m
c = —
V
where:
C = concentration (mg/L)
m = mass (mg)
V = volume (L)
Equation 2
From pure compound,
(
C =
V
where:
C = concentration (mg/L)
m = mass (mg)
V = volume (L)
gf= gravimetric factor (the weight fraction of the analyte in the
compound)
7.10.1 Aluminum solution, stock, 1 ml = 1000 ug AI-Dissolve 1.000 g of
aluminum metal, weighed accurately to at least four significant figures, in
an acid mixture of 4.0 ml of (1 +1) HCI and 1 ml of concentrated HN03 in
a beaker. Warm beaker slowly to effect solution. When dissolution is
January 2001 Draft ~
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Method 200.7
complete, transfer solution quantitatively to a 1-L flask, add an additional
10.0 ml of (1 +1) HCI and dilute to volume with reagent water.
7.10.2 Antimony solution, stock, 1 ml = 1000 ug Sb-Dissolve 1.000 g of
antimony powder, weighed accurately to at least four significant figures, in
20.0 ml (1+1) HN03 and 10.0 ml concentrated HCI. Add 100 ml reagent
water and 1.50 g tartaric acid. Warm solution slightly to effect complete
dissolution. Cool solution and add reagent water to volume in a 1-L
volumetric flask.
7.10.3 Arsenic solution, stock, 1 ml = 1000 ug As-Dissolve 1.320 g of As203 (As
fraction = 0.7574), weighed accurately to at least four significant figures,
in 100 ml of reagent water containing 10.0 ml concentrated NH4OH.
Warm the solution gently to effect dissolution. Acidify the solution with
20.0 ml concentrated HN03 and dilute to volume in a 1-L volumetric flask
with reagent water.
7.10.4 Barium solution, stock, 1 ml = 1000 ug Ba-Dissolve 1.437 g BaC03 (Ba
fraction = 0.6960), weighed accurately to at least four significant figures,
in 150 ml (1+2) HN03 with heating and stirring to de-gas and dissolve
compound. Let solution cool and dilute with reagent water in 1-L
volumetric flask.
7.10.5 Beryllium solution, stock, 1 mL = 1000 ug Be-DO NOT DRY. Dissolve
19.66 g BeSCy4H20 (Be fraction = 0.0509), weighed accurately to at
least four significant figures, in reagent water, add 10.0 mL concentrated
HN03, and dilute to volume in a 1 -L volumetric flask with reagent water.
7.10.6 Boron solution, stock, 1 mL = 1000 ug B-DO NOT DRY. Dissolve 5.716 g
anhydrous H3B03 (B fraction = 0.1749), weighed accurately to at least
four significant figures, in reagent water and dilute in a 1-L volumetric
flask with reagent water. Transfer immediately after mixing to a clean
FEP bottle to minimize any leaching of boron from the glass volumetric
container. Use of a non-glass volumetric flask is recommended to avoid
boron contamination from glassware.
7.10.7 Cadmium solution, stock, 1 mL = 1000 ug Cd-Dissolve 1.000 g Cd metal,
acid cleaned with (1+9) HN03, weighed accurately to at least four
significant figures, in 50 mL (1 +1) HN03 with heating to effect dissolution.
Let solution cool and dilute with reagent water in a 1 -L volumetric flask.
7.10.8 Calcium solution, stock, 1 mL = 1000 ug Ca-Suspend 2.498 g CaC03
(Ca fraction = 0.4005), dried at 180°C for one hour before weighing,
weighed accurately to at least four significant figures, in reagent water
and dissolve cautiously with a minimum amount of (1 +1) HN03. Add
16 Draft January 2001
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Method 200.7
10.0 ml concentrated HN03 and dilute to volume in a 1-L volumetric flask
with reagent water.
7.10.9 Cerium solution, stock, 1 ml = 1000 ug Ce-Make a slurry of 1.228 g
Ce02 (Ce fraction = 0.8141), weighed accurately to at least four
significant figures, in 100 ml concentrated HN03 and evaporate to
dryness. Make another slurry of the residue in 20 ml H20, add 50 ml
concentrated HN03, with heat and stirring add 60 ml 50% H202 drop-wise
in 1 ml increments allowing periods of stirring between the 1 ml
additions. Boil off excess H202 before diluting to volume in a 1-L
volumetric flask with reagent water.
7.10.10 Chromium solution, stock, 1 ml = 1000 ug Cr-Dissolve 1.923 g
Cr03 (Cr fraction = 0.5200), weighed accurately to at least four
significant figures, in 120 ml (1+5) HN03. When solution is
complete, dilute to volume in a 1-L volumetric flask with reagent
water.
7.10.11 Cobalt solution, stock, 1 ml = 1000 ug Co-Dissolve 1.000 g Co
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50.0 ml (1 +1) HN03. Let solution
cool and dilute to volume in a 1 -L volumetric flask with reagent
water.
7.10.12 Copper solution, stock, 1 ml = 1000 ug Cu-Dissolve 1.000 g Cu
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50.0 ml (1 +1) HN03 with heating to
effect dissolution. Let solution cool and dilute in a 1-L volumetric
flask with reagent water.
7.10.13 Iron solution, stock, 1 mL = 1000 ug Fe-Dissolve 1.000 g Fe metal,
acid cleaned with (1+1) HCI, weighed accurately to four significant
figures, in 100 mL (1+1) HCI with heating to effect dissolution. Let
solution cool and dilute with reagent water in a 1-L volumetric flask.
7.10.14 Lead solution, stock, 1 mL = 1000 ug Pb-Dissolve 1.599 g
Pb(N03)2 (Pb fraction = 0.6256), weighed accurately to at least four
significant figures, in a minimum amount of (1 +1) HN03. Add 20.0
mL (1 +1) HN03 and dilute to volume in a 1 -L volumetric flask with
reagent water.
7.10.15 Lithium solution, stock, 1 mL = 1000 ug Li-Dissolve 5.324 g Li2C03
(Li fraction = 0.1878), weighed accurately to at least four significant
figures, in a minimum amount of (1 +1) HCI and dilute to volume in
a 1 -L volumetric flask with reagent water.
January 2001 Draft ~
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Method 200.7
7.10.16 Magnesium solution, stock, 1 ml = 1000 ug Mg-Dissolve 1.000 g
cleanly polished Mg ribbon, accurately weighed to at least four
significant figures, in slowly added 5.0 ml (1+1) HCI (CAUTION:
reaction is vigorous). Add 20.0 ml (1+1) HN03 and dilute to
volume in a 1 -L volumetric flask with reagent water.
7.10.17 Manganese solution, stock, 1 ml = 1000 ug Mn-Dissolve 1.000 g
of manganese metal, weighed accurately to at least four significant
figures, in 50 ml (1+1) HN03 and dilute to volume in a 1-L
volumetric flask with reagent water.
7.10.18 Mercury solution, stock, 1 ml = 1000 ug Hg-DO NOT DRY.
CAUTION: highly toxic element. Dissolve 1.354 g HgCI2 (Hg
fraction = 0.7388) in reagent water. Add 50.0 ml concentrated
HN03 and dilute to volume in 1-L volumetric flask with reagent
water.
7.10.19 Molybdenum solution, stock, 1 ml = 1000 ug Mo-Dissolve 1.500 g
Mo03 (Mo fraction = 0.6666), weighed accurately to at least four
significant figures, in a mixture of 100 ml reagent water and 10.0
ml concentrated NH4OH, heating to effect dissolution. Let solution
cool and dilute with reagent water in a 1 -L volumetric flask.
7.10.20 Nickel solution, stock, 1 ml = 1000 ug Ni-Dissolve 1.000 g of
nickel metal, weighed accurately to at least four significant figures,
in 20.0 ml hot concentrated HN03. Cool, and dilute to volume in a
1 -L volumetric flask with reagent water.
7.10.21 Phosphorus solution, stock, 1 ml = 1000 ug P-Dissolve 3.745 g
NH4H2P04 (P fraction = 0.2696), weighed accurately to at least four
significant figures, in 200 ml reagent water and dilute to volume in
a 1 -L volumetric flask with reagent water.
7.10.22 Potassium solution, stock, 1 ml = 1000 ug K-Dissolve 1.907 g KCI
(K fraction = 0.5244) dried at 110°C, weighed accurately to at least
four significant figures, in reagent water, add 20 ml (1 +1) HCI and
dilute to volume in a 1 -L volumetric flask with reagent water.
7.10.23 Selenium solution, stock, 1 ml = 1000 ug Se-Dissolve 1.405 g
Se02 (Se fraction = 0.7116), weighed accurately to at least four
significant figures, in 200 ml reagent water and dilute to volume in
a 1 -L volumetric flask with reagent water.
7.10.24 Silica solution, stock, 1 ml = 1000 ug Si02-D0 NOT DRY.
Dissolve 2.964 g (NH4)2SiF6, weighed accurately to at least four
18 Draft January 2001
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Method 200.7
significant figures, in 200 ml (1+20) HCI with heating at 85°C to
effect dissolution. Let solution cool and dilute to volume in a 1-L
volumetric flask with reagent water.
7.10.25 Silver solution, stock, 1 ml = 1000 ug Ag-Dissolve 1.000 g Ag
metal, weighed accurately to at least four significant figures, in 80
ml (1 +1) HN03 with heating to effect dissolution. Let solution cool
and dilute with reagent water in a 1 -L volumetric flask. Store
solution in amber bottle or wrap bottle completely with aluminum
foil to protect solution from light.
7.10.26 Sodium solution, stock, 1 ml = 1000 ug Na-Dissolve 2.542 g NaCI
(Na fraction = 0.3934), weighed accurately to at least four
significant figures, in reagent water. Add 10.0 ml concentrated
HN03 and dilute to volume in a 1-L volumetric flask with reagent
water.
7.10.27 Strontium solution, stock, 1 ml = 1000 ug Sr-Dissolve 1.685 g
SrC03 (Sr fraction = 0.5935), weighed accurately to at least four
significant figures, in 200 ml reagent water with drop-wise addition
of 100 ml (1 +1) HCI. Dilute to volume in a 1 -L volumetric flask
with reagent water.
7.10.28 Thallium solution, stock, 1 ml = 1000 ug TI-Dissolve 1.303 g
TIN03 (Tl fraction = 0.7672), weighed accurately to at least four
significant figures, in reagent water. Add 10.0 ml concentrated
HN03 and dilute to volume in a 1-L volumetric flask with reagent
water.
7.10.29 Tin solution, stock, 1 ml = 1000 ug Sn-Dissolve 1.000 g Sn shot,
weighed accurately to at least four significant figures, in an acid
mixture of 10.0 ml concentrated HCI and 2.0 ml (1+1) HN03with
heating to effect dissolution. Let solution cool, add 200 ml
concentrated HCI, and dilute to volume in a 1-L volumetric flask
with reagent water.
7.10.30 Titanium solution, stock, 1 ml = 1000 ug Ti-DO NOT DRY.
Dissolve 6.138 g (NH4)2TiO(C204)2»H20 (Ti fraction = 0.1629),
weighed accurately to at least four significant figures, in 100 ml
reagent water. Dilute to volume in a 1 -L volumetric flask with
reagent water.
7.10.31 Vanadium solution, stock, 1 ml = 1000 ug V-Dissolve 1.000 g V
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50 ml (1 +1) HN03 with heating to
January 2001 Draft ~19
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Method 200.7
effect dissolution. Let solution cool and dilute with reagent water to
volume in a 1 -L volumetric flask.
7.10.32 Yttrium solution, stock 1 ml = 1000 ug Y-Dissolve 1.270 g Y203
(Y fraction = 0.7875), weighed accurately to at least four significant
figures, in 50 ml (1+1) HN03, heating to effect dissolution. Cool
and dilute to volume in a 1 -L volumetric flask with reagent water.
7.10.33 Zinc solution, stock, 1 ml = 1000 ug Zn-Dissolve 1.000 g Zn
metal, acid cleaned with (1+9) HN03, weighed accurately to at
least four significant figures, in 50 ml (1 +1) HN03 with heating to
effect dissolution. Let solution cool and dilute with reagent water to
volume in a 1 -L volumetric flask.
7.11 Mixed calibration standard solutions-For the analysis of total recoverable
digested samples, prepare mixed calibration standard solutions by combining
appropriate volumes of the stock solutions in 500 ml volumetric flasks
containing 20 ml (1 +1) HN03 and 20 ml (1 +1) HCI and dilute to volume with
reagent water. Prior to preparing the mixed standards, each stock solution
should be analyzed separately to determine possible spectral interferences or
the presence of impurities. Care should be taken when preparing the mixed
standards to ensure that the elements are compatible and stable together. To
minimize the opportunity for contamination by the containers, it is recommended
that the mixed-standard solutions be transferred to acid-cleaned, never-used
FEP fluorocarbon bottles for storage. Fresh mixed standards should be
prepared, as needed, with the realization that concentrations can change on
aging. Calibration standards not prepared from primary standards must be
initially verified using a certified reference solution. For the recommended
wavelengths listed in Table 1, some typical calibration standard combinations
are given in Table 3.
NOTE: If the addition of silver to the recommended mixed-acid calibration standard results in
an initial precipitation, add 15 mL of reagent water and warm the flask until the solution clears.
For this acid combination, the silver concentration should be limited to 0.5 mg/L.
7.12 Blanks-Three types of blanks are required for the analysis. The calibration
blank is used in establishing the analytical curve, the method blank is used to
assess possible contamination from the sample preparation procedure, and a
rinse blank is used to flush the sample uptake system and nebulizer between
standards, check solutions, and samples to reduce memory interferences.
7.12.1 The calibration and rinse blanks are prepared by acidifying reagent water
to the same concentrations of the acids as used for the standards. The
blanks should be stored separately in FEP bottles.
20 Draft January 2001
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Method 200.7
7.12.2 The method blank is reagent water that is carried through the same entire
preparation scheme as the samples including sample digestion, when
applicable. When the method blank is analyzed, it will contain all the
reagents in the same volumes as the samples.
7.13 Calibration verification (CV) solution-The CV solution is used to verify
instrument performance during analysis. It should be prepared in the same acid
mixture as the calibration standards by combining method analytes at
appropriate concentrations. Silver must be limited to <0.5 mg/L; while potassium
and phosphorus, because of higher MDLs, and silica, because of potential
contamination, should be at concentrations of 10 mg/L. For other analytes a
concentration of 2 mg/L is recommended. The CV solution should be prepared
from the same standard stock solutions used to prepare the calibration
standards and stored in an FEP bottle. Agency programs may specify or request
that additional CV solutions be prepared at specified concentrations in order to
meet particular program needs.
7.14 Reference sample-Analysis of a reference sample is required for initial and
periodic verification of calibration standards or stock standard solutions in order
to verify instrument performance. The reference sample must be obtained from
an outside source different from the standard stock solutions and prepared in the
same acid mixture as the calibration standards. The concentration of the
analytes in the reference sample solution should be >1 mg/L, except silver,
which must be limited to a concentration of 0.5 mg/L for solution stability. The
reference sample solution should be stored in a FEP bottle and analyzed as
needed to meet data-quality needs. A fresh solution should be prepared
quarterly or more frequently as needed. Alternatively, the reference sample may
be a standard or certified reference material traceable to the National Institute of
Standards and Technology.
7.15 Spectral interference check (SIC) solutions-SIC solutions containing (a) 300
mg/L Fe; (b) 200 mg/L Al; (c) 50 mg/L Ba; (d) 50 mg/L Be; (e) 50 mg/L Cd; (f) 50
mg/L Ce; (g) 50 mg/L Co; (h) 50 mg/L Cr; (i) 50 mg/L Cu; (j) 50 mg/L Mn; (k) 50
mg/L Mo; (I) 50 mg/L Ni; (m) 50 mg/L Sn; (n) 50 mg/L Si02; (o) 50 mg/L Ti;
(p) 50 mg/L TI and (q) 50 mg/L V should be prepared in the same acid mixture
as the calibration standards and stored in FEP bottles. These solutions can be
used to periodically verify a partial list of the on-line (and possible off-line) inter-
element spectral correction factors for the recommended wavelengths given in
Table 1. Other solutions could achieve the same objective as well. Multi-
element SIC solutions may be prepared and substituted for the single element
solutions provided an analyte is not subject to interference from more than one
interferant in the solution (Reference 3).
January 2001 Draft 21
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Method 200.7
NOTE: If wavelengths other than those recommended in Table 1 are used, solutions other than
those above (a through q) may be required.
7.16 Plasma solution-The plasma solution is used for determining the optimum
viewing height of the plasma above the work coil prior to using the method
(Section 10.2). The solution is prepared by adding a 5 ml aliquot from each of
the stock standard solutions of arsenic, lead, selenium, and thallium to a mixture
of 20 ml (1 +1) HN03 and 20 ml (1 +1) HCI and diluting to 500 ml with reagent
water. Store in a FEP bottle.
8.0 Sample Collection, Preservation, and Storage
8.1 Prior to the collection of an aqueous sample, consideration should be given to
the type of data required, (i.e., dissolved or total recoverable), so that
appropriate preservation and pretreatment steps can be taken. The pH of all
aqueous samples must be tested immediately prior to withdrawing an aliquot for
processing or "direct analysis" to ensure the sample has been properly
preserved. If properly acid preserved, the sample can be held up to six months
before analysis.
NOTE: Do not dip pH paper or a pH meter into the sample; remove a small aliquot with a
clean pipette and test the aliquot.
8.2 For the determination of the dissolved elements, a sample must be filtered
through a 0.45 urn pore diameter membrane filter at the time of collection or as
soon thereafter as practically possible. (Glass or plastic filtering apparatus is
recommended to avoid possible contamination. Only plastic apparatus should
be used when the determinations of boron and silica are critical). Use a portion
of the filtered sample to rinse the filter flask, discard this portion and collect the
required volume of filtrate. Acidify the filtrate with (1 +1) HN03 to pH <2
immediately following filtration.
8.3 For the determination of total recoverable elements in aqueous samples,
samples are not filtered, but acidified with (1 +1) HN03 to pH <2 (normally, 3 ml
of (1 +1) acid per liter of sample is sufficient for most ambient and drinking water
samples). Preservation may be done at the time of collection. However, to
avoid the hazards of strong acids in the field, transport restrictions, and possible
contamination, it is recommended that samples be returned to the laboratory
within two weeks of collection and acid preserved upon receipt in the laboratory.
Following acidification, the sample should be mixed, held for 16 hours, and then
verified to be pH <2 just prior to withdrawing an aliquot for processing or "direct
analysis." If, for some reason such as high alkalinity, the sample pH is verified
to be >2, more acid must be added, and the sample held for 16 hours until
verified to be pH <2.
22 Draft January2001
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Method 200.7
NOTE: When the nature of the sample is either unknown or is known to be hazardous,
acidification should be done in a fume hood.
8.4 Solid samples require no preservation prior to analysis other than storage at
4°C. There is no established holding time limitation for solid samples.
8.5 A field blank should be prepared and analyzed as required by the data user.
Use the same conditions (i.e., container, filtration and preservation) as used in
sample collection.
8.6 If a total solids determination is required, then a separate aliquot should be
collected following the procedure given in Section 8.0 of Appendix A.
9.0 Quality Assurance/Quality Control
9.1 Each laboratory that uses this method is required to operate a formal quality
assurance program (Reference 24). The minimum requirements of this program
consist of an initial demonstration of laboratory capability, analysis of samples
spiked with analyte(s) of interest to evaluate and document data quality, and
analysis of standards and blanks as tests of continued performance. Laboratory
performance is compared to established performance criteria to determine that
results of the analysis meet the performance characteristics of the method.
9.1.1 The analyst shall make an initial demonstration of the ability to generate
acceptable accuracy and precision with this method. This ability is
established as described in Section 9.2.
9.1.2 In recognition of advances that are occurring in analytical technology, the
analyst is permitted to exercise certain options to eliminate interferences
or lower the costs of measurements. These options include alternate
digestion, preconcentration, cleanup procedures, and changes in
instrumentation. Alternate determinative techniques, such as the
substitution of a colorimetric technique or changes that degrade method
performance, are not allowed. If an analytical technique other than the
techniques specified in this method is used, then that technique must
have a specificity equal to or better than the specificity of the techniques
in this method for the analytes of interest.
9.1.2.1 Each time the method is modified, the analyst is required to
repeat the procedure in Section 9.2. If the change will affect
the detection limit of the method, the laboratory is required
to demonstrate that the MDL (40 CFR Part 136, Appendix B)
is lower than the MDL for that analyte in this method, or one-
third the regulatory compliance level, whichever is higher. If
January 2001 Draft ~
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Method 200.7
the change will affect calibration, the analyst must
recalibrate the instrument according to Section 10.0.
9.1.2.2 The laboratory is required to maintain records of
modifications made to this method. These records include
the following, at a minimum:
9.1.2.2.1 The names, titles, addresses, and telephone numbers
of the analyst(s) who performed the analyses and
modification, and of the quality control officer who
witnessed and will verify the analyses and
modification.
9.1.2.2.2 A listing of analytes measured, by name and CAS
Registry number.
9.1.2.2.3 A narrative stating the reason(s) for the
modification(s).
9.1.2.2.4 Results from all quality control (QC) tests comparing
the modified method to this method, including:
(a) Method detection limit
(b) Calibration
(c) Calibration verification
(d) Initial precision and recovery
(e) Ongoing precision and recovery
(f) Analysis of blanks
(g) Matrix spike and matrix spike duplicate
analyses
9.1.2.2.5 Data that will allow an independent reviewer to
validate each determination by tracing the instrument
output (peak height, area, or other signal) to the final
result. These data are to include, where possible:
(a) Sample numbers and other identifiers
(b) Digestion/preparation or extraction dates
(c) Analysis dates and times
(d) Analysis sequence/run chronology
(e) Sample weight or volume
(f) Volume before the extraction/concentration
step
(g) Volume after each extraction/concentration
step
24 Draft January 2001
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Method 200.7
(h) Final volume before analysis
(i) Injection volume
(j) Dilution data, differentiating between dilution of
a sample or extract
(k) Instrument and operating conditions (make,
model, revision, modifications)
(I) Sample introduction system (ultrasonic
nebulizer, flow injection system, etc.)
(m) Preconcentration system
(n) Operating conditions (background corrections,
temperature program, flow rates, etc.)
(o) Detector (type, operating conditions, etc.)
(p) Mass spectra, printer tapes, and other
recordings of raw data
(q) Quantitation reports, data system outputs, and
other data to link raw data to results reported
9.1.3 Analyses of blanks are required to demonstrate freedom from
contamination. Section 9.6 describes the required types, procedures, and
criteria for analysis of blanks.
9.1.4 Analyses of MS and MSD samples are required to demonstrate the
accuracy and precision of the method and to monitor for matrix
interferences (Section 9.5). When results of these spikes indicate atypical
method performance for samples, an alternative extraction or cleanup
technique must be used to bring method performance within acceptable
limits. If method performance cannot be brought within the limits given in
this method, the result may not be reported for regulatory compliance
purposes.
9.1.5 The laboratory shall, on an ongoing basis, demonstrate through
calibration verification (Section 9.3) and through analysis of the OPR
standard (Section 9.7) that the analytical system is meeting the
performance criteria.
9.1.6 The laboratory shall maintain records to define the quality of data that are
generated. Development of accuracy statements is described in Sections
9.5.5.1 and 9.7.7.
9.1.7 All samples must be associated with an acceptable OPR, MS/MSD, IPR,
and uncontaminated blanks.
9.2 Initial demonstration of laboratory capability.
January 2001 Draft 25
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Method 200.7
9.2.1 Method detection limit-To establish the ability to detect the analyte(s) of
interest, the analyst shall determine the MDL for each analyte according
to the procedure in 40 CFR 136, Appendix B using the apparatus,
reagents, and standards that will be used in the practice of this method.
The laboratory must produce an MDL that is less than or equal to the
MDL specified in Table 4 (to be determined by the validation study) or
one-third the regulatory compliance limit, whichever is greater. MDLs
must be determined when a new operator begins work or whenever a
change in instrument hardware or operating conditions is made that may
affect the MDL. MDLs must be determined for solids with clean sand or
soil matrix if solid samples are to be run and/or with a reagent water
matrix if aqueous samples are to be run. MDLs also must be determined
for biosolids with peat moss if sludge samples are to be analyzed for
arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium,
and zinc.
9.2.2 Initial precision and recovery (IPR)-To establish the ability to generate
acceptable precision and recovery, the analyst shall perform the following
operations.
9.2.2.1 Spike four aliquots of reagent water (for aqueous samples)
or clean sand or soil (for solid samples) or peat moss (for
biosolid samples) with the analyte(s) of interest at one to
five times the ML. Analyze the four aliquots according to the
procedures in Section 11.0. This test must use the
containers, labware, and reagents that will be used with
samples and all digestion, extraction, and concentrations
steps.
9.2.2.2 Using the results of the four analyses, compute the average
percent recovery (X) for the analyte(s) in each aliquot and
the standard deviation of the recovery (s) for each analyte.
9.2.2.3 For each analyte, compare s and X with the corresponding
limits for IPR in (Table 5- to be determined in validation
study). If s and X for all analyte(s) meet the acceptance
criteria, system performance is acceptable and analysis of
blanks and samples may begin. If, however, any individual
s exceeds the precision limit or any individual X falls outside
the range for accuracy, system performance is unacceptable
for that analyte. Correct the problem and repeat the test.
9.2.3 Linear dynamic range (LDR)-The upper limit of the LDR must be
established for each wavelength used. It must be determined from a
linear calibration prepared in the normal manner using the established
26 Draft January 2001
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Method 200.7
analytical operating procedure for the instrument. The LDR should be
determined by analyzing successively higher standard concentrations of
the analyte until the observed analyte concentration is no more than 10%
below the stated concentration of the standard. LDRs must be
documented and kept on file. The LDR which may be used for the
analysis of samples should be judged by the analyst from the resulting
data. Calculated sample analyte concentrations that are greater than
90% of the determined upper LDR limit must be diluted and analyzed
again. The LDRs should be verified annually or whenever, in the
judgement of the analyst, a change in analytical performance caused by
either a change in instrument hardware or operating conditions would
dictate they should be redetermined.
9.2.4 Reference sample-When beginning the use of this method, quarterly, and
as needed to meet data quality requirements, the analyst must verify the
calibration standards and acceptable instrument performance with the
preparation and analysis of a reference sample (Section 7.14). To verify
the calibration standards, the determined mean concentration from three
analyses of the reference sample must be within ±5% of the stated
reference sample value. If the reference sample is not within the required
limits, an immediate second analysis of the reference sample is
recommended to confirm unacceptable performance. If both the
calibration standards and acceptable instrument performance cannot be
verified, the source of the problem must be identified and corrected before
proceeding with further analyses.
9.3 Calibration verification-A laboratory must analyze a CV solution (Section 7.13)
and a calibration blank (Section 7.12.1) immediately following daily calibration,
after every 10th sample (or more frequently, if required), and at the end of the
sample run. The analysis data of the calibration blank and CV solution must be
kept on file with the sample analyses data.
9.3.1 The result of the calibration blank should be less than the analyte ML or
one-third the regulatory compliance level, whichever is greater.
9.3.2 Analysis of the CV solution immediately following calibration must verify
that the instrument is within performance criteria (to be determined by the
validation study) (Table 5).
9.3.3 If the calibration cannot be verified within the specified limits, both the CV
solution and the calibration blank should be analyzed again. If the
second analysis of the CV solution or the calibration blank confirm
calibration to be outside the limits, sample analysis must be discontinued,
the cause determined, corrected, and/or the instrument recalibrated. All
January 2001 Draft 27
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Method 200.7
samples following the last acceptable CV solution must be analyzed
again.
9.4 Spectral interference check (SIC) solution-For all determinations the laboratory
must periodically verify the inter-element spectral interference correction routine
by analyzing SIC solutions (Section 7.15).
9.4.1 For interferences from iron and aluminum, only those correction factors
(positive or negative) which, when multiplied by 100, exceed the analyte
ML, or one-third the regulatory compliance, whichever is greater, or fall
below the lower limit for the calibration blank, need be tested on a daily
basis. The lower calibration blank control limit is determined by
subtracting the ML, or one-third the regulatory compliance limit, whichever
is greater, from zero.
9.4.2 For the other interfering elements, only those correction factors (positive
or negative) which, when multiplied by 10 to calculate apparent analyte
concentrations that exceed the analyte ML, or one-third the regulatory
compliance, whichever is greater, or fall below the lower limit for the
calibration blank, need be tested on a daily basis.
9.4.3 If the correction routine is operating properly, the determined apparent
analyte(s) concentration from analysis of each interference solution
(Section 7.15, a through q) should fall within a specific concentration
range bracketing the calibration blank. This concentration range is
calculated by multiplying the concentration of the interfering element by
the value of the correction factor being tested and dividing by 10. If, after
subtraction of the analyte ML, or one-third the regulatory compliance,
whichever is greater, the apparent analyte concentration is outside
(above or below) this range, a change in the correction factor of more
than 10% should be suspected. The cause of the change should be
determined and corrected and the correction factor should be updated.
NOTE: The SIC solution should be analyzed more than once to confirm a change has
occurred, with adequate rinse time between solutions and before subsequent analysis of the
calibration blank.
9.4.4 If the correction factors as tested on a daily basis are found to be within
the 10% criteria for five consecutive days, the required verification
frequency of those factors in compliance may be extended to a weekly
basis. Also, if the nature of the samples analyzed is such (e.g., finished
drinking water) that they do not contain concentrations of the interfering
elements at the 10 mg/L level, daily verification is not required; however,
28 Draft January 2001
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Method 200.7
all inter-element spectral correction factors must be verified annually and
updated if necessary.
9.4.5 All inter-element spectral correction factors must be verified whenever
there is a change in instrument operating conditions. Examples of
changes requiring rigorous verification of spectral correction factors are:
changes in incident power, changes in nebulizer gas flow rate, or
installation of a new torch injector with a different orifice.
9.4.6 If the instrument does not display negative concentration values, fortify
the SIC solutions with the elements of interest at 1 mg/L and test for
analyte recoveries that are below 95%. In the absence of measurable
analyte, over-correction could go undetected because a negative value
could be reported as zero.
9.4.7 For instruments without inter-element correction capability or when inter-
element corrections are not used, SIC solutions (containing similar
concentrations of the major components in the samples, e.g., >10 mg/L)
can serve to verify the absence of effects at the wavelengths selected.
These data must be kept on file with the sample analysis data. If the SIC
solution confirms an operative interference that is >10% of the analyte
concentration, the analyte must be determined using a wavelength and
background correction location free of the interference or by another
approved test procedure. Users are advised that high salt concentrations
can cause analyte signal suppressions and confuse interference tests.
9.5 Matrix spike (MS) and matrix spike duplicates (MSD)-To assess the performance
of the method on a given sample matrix, the laboratory must spike, in duplicate,
a minimum of 10% (one sample in 10) of the samples from a given sampling site
or, if for compliance monitoring, from a given discharge. Blanks may not be
used for MS/MSD analysis.
9.5.1 The concentration of the MS and MSD shall be determined as follows:
9.5.1.1 If, as in compliance monitoring, the concentration of
analytes in the sample is being checked against a regulatory
concentration limit, the spiking level shall be at that limit or
at 1-5 times the background concentration of the sample,
whichever is greater. (For notes on Ag, Sn, and Ba see
Sections 1.7, 1.8, and 1.9).
9.5.1.2 If the concentration of analytes in a sample is not being
checked against a regulatory concentration limit, the spike
shall be at 1-5 times the background concentration.
January 2001 Draft ~29
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Method 200.7
9.5.1.3 For solid and sludge samples, the concentration added
should be expressed as mg/kg and is calculated for a one
gram aliquot by multiplying the added analyte concentration
in solution (mg/L) by the conversion factor 100 (mg/L x
0. 1 L/0.001 kg = 1 00, Section 1 2.5). (For notes on Ag, Sn,
and Ba see Sections 1 .7, 1 .8, and 1 .9).
9.5.2 Assessing spike recovery.
9.5.2.1 To determine the background concentration (B), analyze
one sample aliquot from each set of 10 samples from each
site or discharge according to the procedure in Section 1 1 .
If the expected background concentration is known from
previous experience or other knowledge, the spiking level
may be established a priori.
NOTE: The concentrations of calcium, magnesium, sodium and strontium in environmental
waters, along with iron and aluminum in solids and sludge can vary greatly and are not
necessarily predictable. Major constituents should not be spiked to >25 mg/L so that the sample
matrix is not altered and the analysis is not affected. _
9.5.2.2 Prepare a standard solution to produce an appropriate
concentration in the sample (Section 9.5.1).
9.5.2.3 Spike two additional sample aliquots with the spiking
solution and analyze these aliquots as described in Section
1 1 to determine the concentration after spiking (A).
9.5.2.4 Calculate the percent recovery (P) in each aliquot (Equation
3).
Equation 3
(A-B)
v
T
where:
P = Percent recovery
A = Measured concentration of analyte after spiking
B = Measured concentration of analyte before spiking
_ T = True concentration of the spike _
9.5.3 Compare the percent recovery with the QC acceptance criteria in Table 5
(to be determined in validation study).
30 Draft January 2001
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Method 200.7
9.5.3.1 If P falls outside the designated range for recovery in Table
5, the results have failed to meet the established
performance criteria. If P is unacceptable, analyze the OPR
standard (Section 9.7). If the OPR is within established
performance criteria (Table 5), the analytical system is
within specification and the problem can be attributed to
interference by the sample matrix. The data user should be
informed that the result for that analyte in the unfortified
sample is suspect due to either the heterogeneous nature of
the sample or matrix effects, and analysis by method of
standard addition or the use of an internal standard(s)
(Section 11.6) should be considered.
9.5.3.2 If the results of both the spike and the OPR test fall outside
the acceptance criteria, the analytical system is judged to be
outside specified limits. The analyst must identify and
correct the problem and analyze the sample batch again.
9.5.4 Assess the possible need for the method of standard additions (MSA) or
internal standard elements by the following tests. Directions for using
MSA or internal standard(s) are given in Section 11.6.
9.5.4.1 Analyte addition test: An analyte(s) standard added to a
portion of a prepared sample, or its dilution, should have a
recovery of 85% to 115% of the known value. The
analyte(s) addition should produce a minimum level of 20
times and a maximum level of 100 times the method
detection limit. If the analyte addition is <20% of the sample
analyte concentration, the dilution test described in Section
9.5.4.2 should be used. If recovery of the analyte(s) is not
within the specified limits, a matrix effect should be
suspected, and the associated data flagged accordingly.
The method of additions or the use of an appropriate
internal standard element may provide more accurate data.
9.5.4.2 Dilution test: If the analyte concentration is sufficiently high
(minimally, a factor of 50 above the instrument detection
limit in the original solution but <90% of the linear limit), an
analysis of a 1+4 dilution should agree (after correction for
the fivefold dilution) within ±10% of the original
determination. If not, a chemical or physical interference
effect should be suspected and the associated data flagged
accordingly. The method of standard additions or the use of
an internal-standard element may provide more accurate
data for samples failing this test.
January 2001 Draft ~
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Method 200.7
9.5.5 Recovery for samples should be assessed and records maintained.
9.5.5.1 After the analysis of five samples of a given matrix type
(river water, biosolids, etc.). For which the analyte(s) pass
the tests in Section 9.5.3, compute the average percent
recovery (P) and the standard deviation of the percent
recovery (SP) for the analyte(s). Express the accuracy
assessment as a percent recovery interval from P - 2SP to P
+ 2SP for each matrix. For example, if P = 90% and SP =
10% for five analyses of river water, the accuracy interval is
expressed as 70 -110%.
9.5.5.2 Update the accuracy assessment for each metal in each
matrix regularly (e.g., after each five to ten new
measurements).
9.5.6 Precision of matrix spike and duplicate.
9.5.6.1 Relative percent difference between duplicates-Compute
the relative percent difference (RPD) between the MS and
MSD results according to Equation 4 using the
concentrations found in the MS and MSD. Do not use the
recoveries calculated in Section 9.5.2 for this calculation
because the RPD is inflated when the background
concentration is near the spike concentration.
Equation 4
RPD = 200*-
where:
RPD = Relative percent different
D1 = Concentration of the analyte in the MS sample
D2 = Concentration of the analyte in the MSD sample
9.5.6.2 The RPD for the MS/MSD pair must not exceed the
acceptance criterion in Table 5 (to be determined in
validation study). If the criterion is not met, the system is
judged to be outside accepted limits of performance. The
problem must be identified and corrected, and the analytical
batch must be analyzed again.
32 Draft January 2001
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Method 200.7
9.5.6.3 Reference material analysis can provide additional
interference data. The analysis of reference samples is a
valuable tool for demonstrating the ability to perform the
method acceptably. Reference materials containing high
concentrations of analytes can provide additional
information on the performance of the spectral interference
correction routine.
9.6 Blanks.
9.6.1 Method blank.
9.6.1.1 Prepare a method blank with each sample batch (samples of
the same matrix - reagent water for aqueous samples, clean
sand or soil for solid samples, peat moss for biosolid
samples) started through the sample preparation process
(Section 11.0) on the same 12-hour shift, to a maximum of
20 samples). Analyze the blank immediately after the OPR
is analyzed (Section 9.7) to demonstrate freedom from
contamination.
9.6.1.2 If the analyte(s) of interest or any potentially interfering
substance is found in the method blank at a concentration
equal to or greater than the ML (Table 4, to be determined
by the validation study) or 1/3 the regulatory compliance
level, whichever is greater, sample analysis must be halted,
the source of the contamination determined, the samples
must be prepared again with a fresh method blank and OPR
and analyzed again.
9.6.1.3 Alternatively, if a sufficient number of blanks (three
minimum) are analyzed to characterize the nature of a
blank, the average concentration plus two standard
deviations must be less than the regulatory compliance
level.
9.6.1.4 If the result for a single blank remains above the ML or if the
result for the average concentration plus two standard
deviations of three or more blanks exceeds the regulatory
compliance level, results for samples associated with those
blanks may not be reported for regulatory compliance
purposes.
9.6.2 Field blank.
January 2001 Draft ~
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Method 200.7
9.6.2.1 Analyze the field blank(s) shipped with each set of samples
(samples collected from the same site at the same time, to a
maximum of 20 samples). Analyze the blank immediately
before analyzing the samples in the batch.
9.6.2.2 If the analyte(s) of interest or any potentially interfering
substance is found in the field blank at a concentration
equal to or greater than the ML or greater than one-fifth the
level in the associated sample, whichever is greater, results
for associated samples may be the result of contamination
and may not be reported for regulatory compliance
purposes.
9.6.2.3 Alternatively, if a sufficient number of field blanks (three
minimum) are analyzed to characterize the nature of the
field blank, the average concentration plus two standard
deviations must be less than the regulatory compliance level
or less than one-half the level in the associated sample,
whichever is greater.
9.6.2.4 If contamination of the field blanks and associated samples
is known or suspected, the laboratory should communicate
this to the sampling team so that the source of
contamination can be identified and corrective measures
taken prior to the next sampling event.
9.6.3 Equipment blanks-Before any sampling equipment is used at a given site,
it is recommended that the laboratory or cleaning facility generate
equipment blanks to demonstrate that the sampling equipment is free
from contamination. Two types of equipment blanks are recommended:
bottle blanks and sampler check blanks.
9.6.3.1 Bottle blanks-After undergoing appropriate cleaning
procedures (Section 6.10), bottles should be subjected to
conditions of use to verify the effectiveness of the cleaning
procedures. A representative set of sample bottles should
be filled with reagent water acidified to pH < 2 and allowed
to stand for a minimum of 24 hours. Ideally, the time that
the bottles are allowed to stand should be as close as
possible to the actual time that sample will be in contact with
the bottle. After standing, the water should be analyzed for
any signs of contamination. If any bottle shows signs of
contamination, the problem must be identified, the cleaning
procedures corrected or cleaning solutions changed, and all
affected bottles cleaned again.
34 Draft January 2001
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Method 200.7
9.6.3.2 Sampler check blanks-Sampler check blanks are generated
in the laboratory or at the equipment cleaning contractor's
facility by processing reagent water through the sampling
devices using the same procedures that are used in the
field.
9.6.3.2.1 Sampler check blanks are generated by filling a large
carboy or other container with reagent water (Section
7.1) and processing the reagent water through the
equipment using the same procedures that are used
in the field. For example, manual grab sampler check
blanks are collected by directly submerging a sample
bottle into the water, filling the bottle, and capping.
Subsurface sampler check blanks are collected by
immersing the sampler into the water and pumping
water into a sample container. Whatever precautions
and equipment are used in the field should also be
used to generate these blanks.
9.6.3.2.2 The sampler check blank should be analyzed using
the procedures in this method. If the target analyte(s)
or any potentially interfering substance is detected in
the blank, the source of contamination or interference
must be identified and the problem corrected. The
equipment should be demonstrated to be free from
contamination before the equipment is used in the
field.
9.6.3.2.3 Sampler check blanks should be run on all equipment
that will be used in the field. If, for example, samples
are to be collected using both a grab sampling device
and a subsurface sampling device, a sampler check
blank must be run on both pieces of equipment.
9.7 Ongoing precision and recovery.
9.7.1 For aqueous samples, prepare an OPR sample (laboratory fortified
method blank) identical to the IPR aliquots (Section 9.2.2.1) with each
preparation batch (samples of the same matrix started through the sample
preparation process (Section 11.0) on the same 12-hour shift, to a
maximum of 20 samples) by spiking an aliquot of reagent water with the
analyte(s) of interest.
9.7.2 For solid samples, the use of clean sand or soil fortified as in Section
9.7.1 is recommended.
January 2001 Draft ~
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Method 200.7
9.7.3 For biosolid samples, the use of peat moss fortified as in Section 9.7.1 is
recommended.
9.7.4 Analyze the OPR sample immediately before the method blank and
samples from the same batch.
9.7.5 Compute the percent recovery of each analyte in the OPR sample.
9.7.6 For each analyte, compare the concentration to the limits for ongoing
recovery in (Table 5 - to be determined in validation study). If all
analyte(s) meet the acceptance criteria, system performance is
acceptable and analysis of blanks and samples may proceed. If,
however, any individual recovery falls outside of the range given, the
analytical processes are not being performed properly for that analyte.
Correct the problem, prepare the sample batch again with fresh OPR and
method blank, and reanalyze the QA/QC and samples.
9.7.7 Add results that pass the specifications in Section 9.7.6 to IPR and
previous OPR data for each analyte in each matrix. Update QC charts to
form a graphic representation of continued laboratory performance.
Develop a statement of laboratory accuracy for each analyte in each
matrix type by calculating the average percent recovery (P) and the
standard deviation of percent recovery (SP). Express the accuracy as a
recovery interval from P - 2SP to P + 2SP. For example, if P = 95% and
SP = 5%, the accuracy is 85 -105%.
10.0 Calibration and Standardization
10.1 For initial and daily operation, calibrate the instrument according to the
instrument manufacturer's recommended procedures, using mixed calibration
standard solutions (Section 7.11).
10.2 The calibration line should include at least three non-zero points with the high
standard near the upper limit of the linear dynamic range (Section 9.2.3) and the
low standard that contains the analyte(s) of interest at the ML (Section 1.12,
Table 4, to be determined during the validation study). Replicates of a
calibration blank (Section 7.13.1) and the highest standard provide an optimal
distribution of calibration standards to minimize the confidence band for a
straight-line calibration in a response region with uniform variance (Reference
20).
10.3 Calculate the slope and intercept of a line using weighted linear regression. Use
the inverse of the standard's concentration squared (1/x2) as the weighting
factor. The calibration is acceptable if the R2 is greater than 0.995 and the
absolute value of the intercept is less than the MDL for the target analyte. If
36 Draft January 2001
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Method 200.7
these conditions are not met, then the laboratory may not report data analyzed
under that calibration and must recalibrate the instrument.
10.4 The concentration of samples is determined using Equation 5.
Equation 5
y = mx + b
where y = sample concentration
m = slope (calculated In Section 10.3)
x = instrument response
_ b = Intercept (calculated In Section 10.3) _
1 0.5 Response factor may be calculated as an alternative to weighted linear regression for
instrument calibration. Calculate the response factor (RF) at each concentration, as
follows:
Equation 6
where:
Rx = Peak height or area
Cy = Concentration of standard x
-X—
10.5.1 Calculate the mean response factor (RFJ, the standard deviation of the
RFm, and the relative standard deviation (RSD) of the mean (Equation 7).
Equation 7
SD
RSD= 100*-
where:
RSD = Relative standard deviation of the mean
SD = Standard deviation of the RFm
RFm = the mean response factor
10.5.2 Performance criteria for the calibration will be calculated after the
validation of the method.
January 2001 Draft 37
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Method 200.7
11.0 Procedure
11.1 Aqueous sample preparation (Dissolved analytes)-For the determination of
dissolved analytes in ground, drinking and surface waters, pipet an aliquot (>20
ml) of the filtered, acid preserved sample into a 50-mL polypropylene centrifuge
tube. Add an appropriate volume of (1 +1) HN03 to adjust the acid concentration
of the aliquot to approximate a 1% (v/v) HN03 solution (e.g., add 0.2 ml (1+1)
HN03 to a 20 ml aliquot of sample). Cap the tube and mix. The sample is now
ready for analysis. Allowance for sample dilution should be made in the
calculations (Section 12). If mercury is to be determined, a separate aliquot
must be additionally acidified to contain 1% (v/v) HCI to match the signal
response of mercury in the calibration standard and reduce memory interference
effects.
NOTE: If a precipitate is formed during acidification, transport, or storage, the sample aliquot
must be treated using the procedure described in Sections 11.2.2 through 11.2.7 prior to
analysis.
11.2 Aqueous Sample Preparation-Total Recoverable Analytes
11.2.1 For the "direct analysis" of total recoverable analytes in drinking water
samples containing turbidity <1 NTU, treat an unfiltered, acid preserved
sample aliquot using the sample preparation procedure described in
Section 11.1 while making allowance for sample dilution in the data
calculation (Section 12.0). For the determination of total recoverable
analytes in all other aqueous samples or for preconcentrating drinking
water samples prior to analysis, follow the procedure given in
Sections 11.2.2 through 11.2.7.
11.2.2 For the determination of total recoverable analytes in aqueous samples of
>1 NTU turbidity, transfer a 100 ml (±1 ml) aliquot from a well mixed,
acid preserved sample to a 250-mL Griffin beaker. (When necessary,
smaller sample aliquot volumes may be used).
NOTE: If the sample contains undissolved solids >1%, a well mixed, acid preserved aliquot
containing no more than 1 gparticulate material should be cautiously evaporated to near 10 mL
and extracted using the acid-mixture procedure described in Sections 11.3.3 through 11.3.6.
11.2.3 Add 2 mL (1+1) HN03 and 1.0 mL of (1+1) HCI to the beaker containing
the measured volume of sample. Place the beaker on the hot plate for
solution evaporation. The hot plate should be located in a fume hood and
previously adjusted to provide evaporation at a temperature of
approximately but no higher than 85°C. (See the following note). The
beaker should be covered with an elevated watch glass or other
38 Draft January2001
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Method 200.7
necessary steps should be taken to prevent sample contamination from
the fume hood environment.
NOTE: For proper heating, adjust the temperature control of the hot plate such that an
uncovered Griffin beaker containing 50 mL of water placed in the center of the hot plate can be
maintained at a temperature approximately but no higher than 85°C. (Once the beaker is
covered with a watch glass, the temperature of the water will rise to approximately 95° C).
11.2.4 Reduce the volume of the sample aliquot to about 20 mL by gentle
heating at 85°C. DO NOT BOIL. This step takes about two hours for a
100 mL aliquot with the rate of evaporation rapidly increasing as the
sample volume approaches 20 mL. (A spare beaker containing 20 mL of
water can be used as a gauge).
11.2.5 Cover the lip of the beaker with a watch glass to reduce additional
evaporation and gently reflux the sample for 30 minutes. (Slight boiling
may occur, but vigorous boiling must be avoided to prevent loss of the
HCI-H20 azeotrope).
11.2.6 Allow the beaker to cool. Quantitatively transfer the sample solution to a
50-mL volumetric flask, dilute to volume with reagent water, stopper and
mix.
11.2.7 Allow any undissolved material to settle overnight, or centrifuge a portion
of the prepared sample until clear. (If after centrifuging or standing
overnight, the sample contains suspended solids that would clog the
nebulizer, a portion of the sample may be filtered for their removal prior to
analysis. However, care should be exercised to avoid potential
contamination from filtration). The sample is now ready for analysis.
Because the effects of various matrices on the stability of diluted samples
cannot be characterized, all analyses should be performed as soon as
possible after the completed preparation.
11.3 Solid sample preparation-Total recoverable analytes
11.3.1 For the determination of total recoverable analytes in solid samples, mix
the sample thoroughly and transfer a portion to a tared weighing dish.
For samples with <35% estimated moisture, a 20 g portion is sufficient.
For samples with estimated moisture >35%, a larger aliquot 50-100 g is
required. Dry the sample to a constant weight at 60°C. The sample is
dried at 60°C to prevent the loss of mercury and other possible volatile
metallic compounds, to facilitate sieving, and to ready the sample for
grinding.
January 2001 Draft 39
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Method 200.7
11.3.2 To achieve homogeneity, sieve the dried sample using a 5-mesh
polypropylene sieve and grind in a mortar and pestle. (The sieve, mortar
and pestle should be cleaned between samples). From the dried, ground
material weigh accurately a representative 1.0 ± 0.01 g aliquot (W) of the
sample and transfer to a 250-mL Phillips beaker for acid extraction
(Sections 1.6, 1.7, 1.8, and 1.9).
11.3.3 To the beaker, add 4 ml of (1+1) HN03 and 10 ml of (1+4) HCI. Cover
the lip of the beaker with a watch glass. Place the beaker on a hot plate
for reflux extraction of the analytes. The hot plate should be located in a
fume hood and previously adjusted to provide a reflux temperature of
approximately 95°C (See the following note).
NOTE: For proper heating, adjust the temperature control of the hot plate such that an
uncovered Griffin beaker containing 50 mL of water placed in the center of the hot plate can be
maintained at a temperature approximately but no higher than 85°C. (Once the beaker is
covered with a watch glass the temperature of the water will rise to approximately 95° C). Also,
a block digester capable of maintaining a temperature of95°C and equipped with 250 mL
constricted volumetric digestion tubes may be substituted for the hot plate and conical beakers in
the extraction step.
11.3.4 Heat the sample and gently reflux for 30 minutes. Very slight boiling may
occur, but vigorous boiling must be avoided to prevent loss of the HCI-
H20 azeotrope. Some solution evaporation will occur (3-4 mL).
11.3.5 Allow the sample to cool and quantitatively transfer the extract to a 100-
ml_ volumetric flask. Dilute to volume with reagent water, stopper and
mix.
11.3.6 Allow the sample extract solution to stand overnight to separate insoluble
material or centrifuge a portion of the sample solution until clear. (If after
centrifuging or standing overnight, the extract solution contains
suspended solids that would clog the nebulizer, a portion of the extract
solution may be filtered for their removal prior to analysis. However, care
should be exercised to avoid potential contamination from filtration). The
sample extract is now ready for analysis. Because the effects of various
matrices on the stability of diluted samples cannot be characterized, all
analyses should be performed as soon as possible after the completed
preparation.
11.3.7 Determine the total solids content of the sample using the procedure in
Appendix A.
11.4 Sludge sample preparation-Total recoverable analytes.
40 Draft January 2001
-------
Method 200.7
NOTE: It may be possible to use the solids digestion (Section 11.3) for sludge samples,
depending on the composition of the sludge sample and the analyte(s) of interest. Under this
performance-based method, it is admissible to change the digestion technique as long as all
quality control and assurance tests meet the criteria published in Tables 4 and 5. This method
has been validated using the sludge sample digestion in Section 11.4 of this method, and it works
for all the analytes listed in Section 1.1.
11.4.1 Determination of total recoverable analytes in sludge samples containing
total suspended solids >1% (w/v).
11.4.1.1 Mix the sample thoroughly and transfer a portion to a tared
weighing dish. For samples with <35% estimated moisture a
20 g portion is sufficient. For samples with estimated
moisture >35% a larger aliquot of 50-100 g is required. Dry
the sample to a constant weight at 60°C. The sample is
dried at 60°C to prevent the loss of mercury and other
possible volatile metallic compounds, to facilitate sieving,
and to ready the sample for grinding.
11.4.1.2 To achieve homogeneity, sieve the dried sample using a 5-
mesh polypropylene sieve and grind in a mortar and pestle.
(The sieve, mortar and pestle should be cleaned between
samples). From the dried, ground material weigh accurately
a representative 1.0 ± 0.01 g aliquot (W) of the sample and
transfer to a 250-mL Phillips beaker for acid extraction
(Sections 1.6, 1.7, 1.8, and 1.9).
11.4.1.3 Add 10 ml of (1 +1) HN03 to the beaker and cover the lip of
the beaker with a watch glass. Place the beaker on a hot
plate and reflux the sample for 10 minutes. Remove the
sample from the hot plate and allow to cool. Add 5 ml of
concentrated HN03 to the beaker, replace the watch glass,
place on a hot plate, and reflux for 30 minutes. Repeat this
last step once. Remove the beaker from the hot plate and
allow the sample to cool. Add 2 ml of reagent water and 3
ml of 30% H202. Place the beaker on a hot plate and heat
the sample until a gentle effervescence is observed. Once
the reaction has subsided, additional 1 ml aliquots of the
30% H202 should be added until no effervescence is
observed, but to no more than a total of 10 ml. Add 2 ml
concentrated HCI and 10 ml of reagent water to the sample,
cover with a watch glass and reflux for 15 minutes.
January 2001 Draft 41
-------
Method 200.7
11.4.1.4 Cool the sample and dilute to 100 ml with reagent water.
Any remaining solid material should be allowed to settle, or
an aliquot of the final sample volume may be centrifuged.
11.4.1.5 Determine the total solids content of the sample using the
procedure in Appendix A.
11.4.2 Determination of total recoverable analytes in sludge samples containing
total suspended solids < 1% (w/v).
11.4.2.1 Transfer 100 ml of well-mixed sample to a 250-mL Griffin
beaker.
11.4.2.2 Add 3 ml of concentrated HN03 and place the beaker on a
hot plate. Heat the sample and cautiously evaporate to a
volume of 5 ml. If the sample contains large amounts of
dissolved solids, adjust this volume upwards to prevent the
sample from going to dryness. Remove the beaker from the
hot plate and allow the sample to cool. Add 3 ml of
concentrated HN03, cover with a watch glass and gently
reflux the sample until the sample is completely digested or
no further changes in appearance occur, adding additional
aliquots of acid if necessary to prevent the sample from
going to dryness. Then remove the watch glass and reduce
the sample volume to 3 ml, again adjusting upwards if
necessary.
11.4.2.3 Cool the beaker, then add 10 m L of reagent water and 4 m L
of (1 +1) HCI to the sample and reflux for 15 minutes. Cool
the sample and dilute to 100 ml with reagent water. Any
remaining solid material should be allowed to settle, or an
aliquot of the final sample volume may be centrifuged.
11.4.2.4 Determine the total solids content of the sample using the
procedure in Appendix A.
11.5 Sample analysis.
11.5.1 Prior to daily calibration of the instrument, inspect the sample introduction
system including the nebulizer, torch, injector tube and uptake tubing for
salt deposits, dirt and debris that would restrict solution flow and affect
instrument performance. Clean the system when needed or on a daily
basis.
11.5.2 Configure the instrument system.
42 Draft January 2001
-------
Method 200.7
11.5.2.1 Specific wavelengths are listed in Table 1. Other
wavelengths may be substituted if they can provide the
needed sensitivity and are corrected for spectral
interference. However, because of the difference among
various makes and models of spectrometers, specific
instrument operating conditions cannot be given. The
instrument and operating conditions utilized for
determination must be capable of providing data of
acceptable quality to the program and data user. The
analyst should follow the instructions provided by the
instrument manufacturer unless other conditions provide
similar or better performance for a task. Operating
conditions for aqueous solutions usually vary from 1100 -
1200 watts forward power, 15-16 mm viewing height, 15 -
19 L/min. argon coolant flow, 0.6 -1 L/min. argon aerosol
flow, 1-1.8 mL/min. sample pumping rate with a one minute
preflush time and measurement time near 1 s per
wavelength peak (for sequential instruments) and near 10 s
per sample (for simultaneous instruments). Use of the
Cu/Mn intensity ratio at 324.754 nm and 257.610 nm (by
adjusting the argon aerosol flow) has been recommended as
a way to achieve repeatable interference correction factors
(Reference 17).
11.5.2.2 Prior to using this method, optimize the plasma operating
conditions. The following procedure is recommended for
vertically configured plasmas. The purpose of plasma
optimization is to provide a maximum signal-to-background
ratio for the least sensitive element in the analytical array.
The use of a mass flow controller to regulate the nebulizer
gas flow rate greatly facilitates the procedure.
11.5.2.3 Ignite the plasma and select an appropriate incident rf
power with minimum reflected power. Allow the instrument
to become thermally stable before beginning. This usually
requires at least 30 to 60 minutes of operation. While
aspirating the 1000 ug/mL solution of yttrium
(Section 7.10.32), follow the instrument manufacturer's
instructions and adjust the aerosol carrier gas flow rate
through the nebulizer so a definitive blue emission region of
the plasma extends approximately from 5-20 mm above the
top of the work coil (Reference 18). Record the nebulizer
gas flow rate or pressure setting for future reference.
January 2001 Draft 43
-------
Method 200.7
11.5.2.4 After establishing the nebulizer gas flow rate, determine the
solution uptake rate of the nebulizer in mL/min. by aspirating
a known volume calibration blank for a period of at least
three minutes. Divide the spent volume by the aspiration
time (in minutes) and record the uptake rate. Set the
peristaltic pump to deliver the uptake rate in a steady even
flow.
11.5.2.5 After horizontally aligning the plasma and/or optically
profiling the spectrometer, use the selected instrument
conditions from Sections 11.5.2.3 and 11.5.2.4, and aspirate
the plasma solution (Section 7.16), containing 10 ug/mL
each of As, Pb, Se and Tl. Collect intensity data at the
wavelength peak for each analyte at 1 mm intervals from 14
-18 mm above the top of the work coil. This region of the
plasma is commonly referred to as the analytical zone
(Reference 19). Repeat the process using the calibration
blank. Determine the net signal to blank intensity ratio for
each analyte for each viewing height setting. Choose the
height for viewing the plasma that provides the largest
intensity ratio for the least sensitive element of the four
analytes. If more than one position provides the same ratio,
select the position that provides the highest net intensity for
the least sensitive element or accept a compromise position
of the intensity ratios of all four analytes.
11.5.2.6 The instrument operating condition finally selected as
optimum should provide the lowest reliable method
detection limits.
11.5.2.7 If either the instrument operating conditions, such as
incident power and/or nebulizer gas flow rate are changed,
or a new torch injector tube having a different orifice i.d. is
installed, the plasma and plasma viewing height should be
reoptimized.
11.5.2.8 Before daily calibration and after the instrument warmup
period, the nebulizer gas flow must be reset to the
determined optimized flow. If a mass flow controller is being
used, it should be reset to the recorded optimized flow rate.
In order to maintain valid spectral inter-element correction
routines, the nebulizer gas flow rate should be the same
from day-to-day (<2% change). The change in signal
intensity with a change in nebulizer gas flow rate for both
44 Draft January 2001
-------
Method 200.7
"hard" (Pb 220.353 nm) and "soft" (Cu 324.754) lines is
illustrated in Figure 1.
11.5.3 The instrument must be allowed to become thermally stable before
calibration and analyses. This usually requires at least 30 to 60 minutes
of operation. After instrument warmup, complete any required optical
profiling or alignment particular to the instrument.
11.5.4 Prior to and during the analysis of samples, the laboratory must comply
with the required QA/QC procedures (Section 9). QA/QC data must be
generated using the same instrument operating conditions (Section 11.5)
and calibration routine (Section 10) in effect for sample analysis. The
data must be documented and kept on file so that they are available for
review by the data user.
11.5.5 A peristaltic pump must be used to introduce all solutions to the nebulizer.
To allow equilibrium to be reached in the plasma, aspirate all solutions for
30 seconds after reaching the plasma before beginning integration of the
background corrected signal to accumulate data. When possible, use the
average value of replicate integration periods of the signal to be
correlated to the analyte concentration. Flush the system with the rinse
blank (Section 7.12.1) fora minimum of 60 seconds (Section 4.4) between
all standard or sample solutions, OPRs, MS, MSD, and check solutions.
11.5.6 Determined sample analyte concentrations that are 90% or more of the
upper limit of the analyte LDR must be diluted with reagent water that has
been acidified in the same manner as calibration blank and analyzed
again.
11.5.7 Also, for the inter-element spectral interference correction routines to
remain valid during sample analysis, the interferant concentration must
not exceed its LDR. If the interferant LDR is exceeded, analyte detection
limits are raised and determination by another approved test procedure
that is either more sensitive and/or interference free is recommended. If
another approved method is unavailable, the sample may be diluted with
acidified reagent water and reanalyzed.
11.5.8 When it is necessary to assess an operative matrix interference (e.g.,
signal reduction due to high dissolved solids), the tests described in
Section 9.5.4 and 11.6 are recommended.
11.5.9 Report data as directed in Section 12.0.
11.6 If the method of standard additions (MSA) is used, standards are added at one
or more levels to portions of a prepared sample. This technique compensates
January 2001 Draft ~5
-------
Method 200.7
for enhancement or depression of an analyte signal by a matrix (Reference 21).
It will not correct for additive interferences such as contamination, inter-element
interferences, or baseline shifts. This technique is valid in the linear range when
the interference effect is constant over the range, the added analyte responds
the same as the endogenous analyte, and the signal is corrected for additive
interferences. The simplest version of this technique is the single-addition
method. This procedure calls for two identical aliquots of the sample solution to
be taken. To the first aliquot, a small volume of standard is added; while to the
second aliquot, a volume of acid blank is added equal to the standard addition.
The sample concentration is calculated with Equation 8.
Equation 8
s~
(Sl-s2)*v2
where:
Cs = Sample concentration (mg/L)
C = Concentration of the standard solution (mg/L)
S1 = Signal for fortified aliquot
S2 = Signal for unfortified aliquot
V1 = Volume of the standard addition (L)
_ Vy = Volume of the sample aliquot (L) used for MSA _
For more than one fortified portion of the prepared sample, linear regression
analysis can be applied using a computer or calculator program to obtain the
concentration of the sample solution. An alternative to using the method of
standard additions is use of the internal standard technique by adding one or
more elements (not in the samples and verified not to cause an uncorrected
inter-element spectral interference) at the same concentration (which is sufficient
for optimum precision) to the prepared samples (blanks and standards) that are
affected the same as the analytes by the sample matrix. Use the ratio of analyte
signal to the internal standard signal for calibration and quantitation.
12.0 Data Analysis and Calculations
12.1 Sample data should be reported in units of mg/L for aqueous samples and mg/kg
dry weight for solid and sludge samples.
1 2.2 For dissolved aqueous analytes (Section 11.1) report the data generated directly
from the instrument with allowance for sample dilution. Do not report analyte
concentrations below the MDL.
12.3 For total recoverable aqueous analytes (Section 1 1 .2), multiply solution analyte
concentrations by the dilution factor 0.5, when 100 ml aliquot is used to produce
46 Draft January 2001
-------
Method 200.7
the 50 mL final solution, and report data as instructed in Section 12.4. If an
aliquot volume other than 100 mL is used for sample preparation, adjust the
dilution factor accordingly. Also, account for any additional dilution of the
prepared sample solution needed to complete the determination of analytes
exceeding 90% or more of the LDR upper limit. Do not report data below the
determined analyte MDL concentration.
12.4 For analytes with MDLs <0.01 mg/L, round the data values to the thousandth
place and report analyte concentrations up to three significant figures. For
analytes with MDLs >0.01 mg/L, round the data values to the hundredth place
and report analyte concentrations up to three significant figures. Extract
concentrations for solids and sludge data should be rounded in a similar manner
before calculations in Section 12.5 are performed.
12.5 For total recoverable analytes in solid and sludge samples (Sections 11.3 and
11.4), round the solution analyte concentrations (mg/L) as instructed in Section
12.4. Report the data up to three significant figures as mg/kg dry-weight basis
unless specified otherwise by the program or data user. Calculate the
concentration using Equation 9.
Equation 9
C*V*D
s~ W
where:
Cs=Sample concentration (mg/kg, dry-weight basis)
C=Concentration in extract (mg/L)
V=Volume of extract (L, 100 mL = 0.1L)
D=Dilution factor (undiluted = 1)
W=Dry weight of sample aliquot extracted (kg, 1g = 0.001kg)
Do not report analyte data below the solids MDL.
12.6 To report percent solids or mg/kg of solid and sludge samples, use the
procedure in Appendix A.
12.7 The QC data obtained during the analyses provide an indication of the quality of
the sample data and should be provided with the sample results.
13.0 Method Performance
13.1 MDLs and MLs will be determined in a validation study. Preliminary MDL values
are given in Table 4. The ML for each analyte can be calculated by multiplying
January 2001 Draft 47
-------
Method 200.7
the MDL by 3.18 and rounding to the number nearest (2, 5, or 10 X 10") where n
is a positive or negative integer.
14.0 Pollution Prevention
14.1 Pollution prevention encompasses any technique that reduces or eliminates the
quantity or toxicity of waste at the point of generation. Numerous opportunities
for pollution prevention exist in laboratory operation. The EPA has established a
preferred hierarchy of environmental management techniques that places
pollution prevention as the management option of first choice. Whenever
feasible, laboratory personnel should use pollution prevention techniques to
address their waste generation (e.g., Section 7.10). When wastes cannot be
feasibly reduced at the source, the Agency recommends recycling as the next
best option.
14.2 For information about pollution prevention that may be applicable to laboratories
and research institutions, 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, (202) 872-4477.
15.0 Waste Management
15.1 The Environmental Protection Agency requires that laboratory waste
management practices be conducted consistent with all applicable rules and
regulations. The Agency urges laboratories to protect the air, water, and land by
minimizing and controlling all releases from hoods and bench operations,
complying with the letter and spirit of any sewer discharge permits and
regulations, and by complying with all solid and hazardous waste 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," available from the American
Chemical Society at the address listed in the Section 14.2.
16.0 References
1. U.S. Environmental Protection Agency. Inductively Coupled Plasma-Atomic
Emission Spectrometric Method for Trace Element Analysis of Water and
Wastes-Method 200.7, Dec. 1982. EPA-600/4-79-020, revised March 1983.
2. U.S. Environmental Protection Agency. Inductively Coupled Plasma Atomic
Emission Spectroscopy Method 6010, SW-846 Test Methods for Evaluating
Solid Waste, 3rd Edition, 1986.
48 Draft January 2001
-------
Method 200.7
3. U.S. Environmental Protection Agency. Method 200.7: Determination of Metals
and Trace Elements in Water and Wastes by Inductively Coupled Plasma-
Atomic Emission Spectrometry, revision 3.3, EPA 600 4-91/010 June 1991.
4. U.S. Environmental Protection Agency. Inductively Coupled Plasma-Atomic
Emission Spectrometry Method for the Analysis of Waters and Solids, EMMC,
July 1992.
5. Fassel, V.A. et al. Simultaneous Determination of Wear Metals in Lubricating
Oils by Inductively-Coupled Plasma Atomic Emission Spectrometry. Anal.
Chem. 48:516-519, 1976.
6. Merryfield, R.N. and R.C. Loyd. Simultaneous Determination of Metals in Oil by
Inductively Coupled Plasma Emission Spectrometry. Anal. Chem. 51:1965-1968,
1979.
7. Winge, R.K. etal. Inductively Coupled Plasma-Atomic Emission Spectroscopy:
An Atlas of Spectral Information, Physical Science Data 20. Elsevier Science
Publishing, New York, New York, 1985.
8. Boumans, P.W.J.M. Line Coincidence Tables for Inductively Coupled Plasma
Atomic Emission Spectrometry, 2nd edition. Pergamon Press, Oxford, United
Kingdom, 1984.
9. 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. Available
from the National Technical Information Service (NTIS) as PB-277256.
10. OSHA Safety and Health Standards, General Industry, (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, (Revised,
January 1976).
11. Safety in Academic Chemistry Laboratories, American Chemical Society
Publication, Committee on Chemical Safety, 3rd Edition, 1979.
12. Proposed OSHA Safety and Health Standards, Laboratories, Occupational
Safety and Health Administration, Federal Register, July 24, 1986.
13. Rohrbough, W.G. et al. Reagent Chemicals, American Chemical Society
Specifications, 7th edition. American Chemical Society, Washington, D.C.,
1986.
January 2001 Draft 49
-------
Method 200.7
14. American Society for Testing and Materials. Standard Specification for Reagent
Water, D1193-77. Annual Book of ASTM Standards, Vol. 11.01. Philadelphia,
PA, 1991.
15. Cocte of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.
16. Maxfield, R. and B. Mindak. EPA Method Study 27, Method 200.7 Trace Metals
by ICP, Nov. 1983. Available from National Technical Information Service
(NTIS) as PB 85-248-656.
17. Botto, R.I., Quality Assurance in Operating a Multielement ICP Emission
Spectrometer. Spectrochim. Acta, 39B(1):95-113, 1984.
18. Wallace, G.F., Some Factors Affecting the Performance of an ICP Sample
Introduction System. Atomic Spectroscopy, Vol. 4, p. 188-192, 1983.
19. Koirtyohann, S.R. et al. Nomenclature System for the Low-Power Argon
Inductively Coupled Plasma, Anal. Chem. 52:1965, 1980.
20. Deming, S.N. and S.L. Morgan. Experimental Design for Quality and
Productivity in Research, Development, and Manufacturing, Part III, pp 119-123.
Short course publication by Statistical Designs, 9941 Rowlett, Suite 6, Houston,
TX 77075, 1989.
21. Winefordner, J.D., Trace Analysis: Spectroscopic Methods for Elements,
Chemical Analysis, Vol. 46, pp. 41-42.
22. Jones, C.L. et al. An Interlaboratory Study of Inductively Coupled Plasma
Atomic Emission Spectroscopy Method 6010 and Digestion Method 3050. EPA-
600/4-87-032, U.S. Environmental Protection Agency, Las Vegas, Nevada,
1987.
23. Martin, T.D., E.R. Martin and S.E. Long. Method 200.2: Sample Preparation
Procedure for Spectrochemical Analyses of Total Recoverable Elements, EMSL
ORD, USEPA, 1989.
24. Handbook of Analytical Quality Control in Water and Wastewater Laboratories]
U.S. Environmental Protection Agency. EMSL-Cincinnati, OH, March 1979.
50 Draft January 2001
-------
Method 200.7
17.0 Tables, Diagrams, Flowcharts, and Validation Data
TABLE 1: WAVELENGTHS, ESTIMATED INSTRUMENT DETECTION
LIMITS,
Analyte
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Cerium
Chromium
Cobalt
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Silica (Si02)
Silver
Sodium
Strontium
Thallium
Tin
Titanium
Vanadium
Zinc
AND RECOMMENDED
Wavelength3
(nm)
308.215
206.833
193.759
493.409
313.042
249.678
226.502
315.887
413.765
205.552
228.616
324.754
259.940
220.353
670.784
279.079
257.610
194.227
203.844
231.604
214.914
766.491
196.090
251.611
328.068
588.995
421.552
190.864
189.980
334.941
292.402
213.856
CALIBRATION
Estimated
Detection
Limit"
(M9/L)
45
32
53
2.3
0.27
5.7
3.4
30
48
6.1
7.0
5.4
6.2
42
3.7d
30
1.4
2.5
12
15
76
700e
75
26d (Si02)
7.0
29
0.77
40
25
3.8
7.5
1.8
Calibrate0
to
(mg/L)
10
5
10
1
1
1
2
10
2
5
2
2
10
10
5
10
2
2
10
2
10
20
5
10
0.5
10
1
5
4
10
2
5
January 2001
Draft
51
-------
Method 200.7
aThe wavelengths listed are recommended because of their sensitivity and
overall acceptability. Other wavelengths may be substituted if they can provide
the needed sensitivity and are treated with the same corrective techniques for
spectral interference (see Section 4.1).
bThese estimated 3-sigma instrumental detection limits are provided only as a
guide to instrumental limits (Reference 16). The method detection limits are
sample dependent and may vary as the sample matrix varies. Detection limits
for solids can be estimated by dividing these values by the grams extracted per
liter, which depends upon the extraction procedure. Divide solution detection
limits by 10 for 1 g extracted to 100 ml for solid detection limits.
Suggested concentration for instrument calibration (Reference 2). Other
calibration limits in the linear ranges may be used.
dCalculated from 2-sigma data (Reference 5).
"Highly dependent on operating conditions and plasma position.
52 Draft January 2001
-------
Method 200.7
TABLE 2: ON-LINE METHOD INTER-ELEMENT SPECTRAL
INTERFERENCES ARISING FROM INTERFERANTS AT THE 100 mg/L
LEVEL
Analyte
Ag
Al
As
B
Ba
Be
Ca
Cd
Ce
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Si02
Sn
Sr
Tl
Ti
V
Zn
Wavelength
(nm)
328.068
308.215
193.759
249.678
493.409
313.042
315.887
226.502
413.765
228.616
205.552
324.754
259.940
194.227
766.491
670.784
279.079
257.610
203.844
588.995
231.604
214.914
220.353
206.833
196.099
251.611
189.980
421.552
190.864
334.941
292.402
213.856
Interferant3
Ce, Ti, Mn
V, Mo, Ce, Mn
V, Al, Co, Fe, Ni
None
None
V, Ce
Co, Mo, Ce
Ni, Ti, Fe, Ce
None
Ti, Ba, Cd, Ni, Cr, Mo, Ce
Be, Mo, Ni
Mo, Ti
None
V, Mo
None
None
Ce
Ce
Ce
None
Co, TI
Cu, Mo
Co, Al, Ce, Cu, Ni, Ti, Fe
Cr, Mo, Sn, Ti, Ce, Fe
Fe
None
Mo, Ti, Fe, Mn, Si
None
Ti, Mo, Co, Ce, Al, V, Mn
None
Mo, Ti, Cr, Fe, Ce
Ni, Cu, Fe
"These on-line interferences from method analytes and titanium only were
observed using an instrument with 0.035 nm resolution (see Section 4.1.2).
Interferant ranked by magnitude of intensity with the most severe interferant
listed first in the row.
January 2001 Draft 53
-------
Method 200.7
TABLE 3: MIXED STANDARD SOLUTIONS
Solution Analytes
I Ag, As, B, Ba, Ca, Cd, Cu, Mn, Sb, and
II Se
III K, Li, Mo, Na, Sr, and Ti
IV Co, P, V, and Ce
V Al, Cr, Hg, Si02, Sn, and Zn
Be, Fe, Mg, Ni, Pb, and TI
54 Draft January 2001
-------
Method 200.7
TABLE 4: TOTAL RECOVERABLE METHOD DETECTION LIMITS (MDL)a
MDLs
Analyte Aqueous, mg/Lb Solids, mg/kgc
Ag
Al
As
Bd
Ba
Be
Ca
Cd
Ce
Co
Cr
Cu
Fe
Hg
K
Li
Mg
Mn
Mo
Na
Ni
P
Pb
Sb
Se
Si02
Sn
Sr
Tl
Ti
V
Y
Zn
0.002
0.02
0.008
0.003
0.001
0.0003
0.01
0.001
0.02
0.002
0.004
0.003
0.03e
0.007
0.3
0.001
0.02
0.001
0.004
0.03
0.005
0.06
0.01
0.008
0.02
0.02
0.007
0.0003
0.001
0.02
0.003
0.002
0.3
3
2
—
0.2
0.1
2
0.2
3
0.4
0.8
0.5
6
2
60
0.2
3
0.2
1
6
1
12
2
2
5
—
2
0.1
0.2
3
1
0.3
a Table will be changed after interlaboratory validation of Method 200.7.
bMDL concentrations are computed for original matrix with allowance for 2x
sample preconcentration during preparation. Samples were processed in PTFE
and diluted in 50-mL plastic centrifuge tubes.
c Estimated, calculated from aqueous MDL determinations.
d Boron not reported because of glassware contamination. Silica not
determined in solid samples.
e Elevated value due to fume-hood contamination.
January 2001 Draft 55
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Method 200.7
TABLE 5: PERFORMANCE CRITERIA FOR METHOD 200.7 (TO BE DETERMINED
DURING INTERLABORATORY VALIDATION)
56 Draft January 2001
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Method 200.7
Pb-Cu ICP-AES EMISSION PROFILE
32
30
28
26
24
22
20 -
18
16 -
14 -
Net Emision Intensity Counts (X10 )
12
475 525 575 625 675 725 775
Nebulizer Argon Flow Rate - mL/min
Figure 1
825
January 2001
Draft
57
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Method 200.7
Appendix A: Total Solids in Solid and Semisolid Matrices
1.0 Scope and Application
1.1 This procedure is applicable to the determination of total solids in such solid and
semisolid samples as soils, sediments, biosolids (municipal sewage sludge)
separated from water and wastewater treatment processes, and sludge cakes
from vacuum filtration, centrifugation, or other biosolids dewatering processes.
1.2 This procedure is taken from EPA Method 1684: Total, Fixed, and Volatile Solids
in Solid and Semi-Solid Matrices.
1.3 Method detection limits (MDLs) and minimum levels (MLs) have not been
formally established for this draft procedure. These values will be determined
during the validation of Method 1684.
1.4 This procedure is performance based. The laboratory is permitted to omit any
step or modify any procedure (e.g. to overcome interferences, to lower the cost
of measurement), provided that all performance requirements in this procedure
are met. Requirements for establishing equivalency are given in Section 9.1.2 of
Method 200.7.
1.5 Each laboratory that uses this procedure must demonstrate the ability to
generate acceptable results using the procedure in Section 9.2.
2.0 Summary of Method
2.1 Sample aliquots of 25-50 g are dried at 103°C to 105°C to drive off water in the
sample.
2.3 The mass of total solids in the sample is determined by comparing the mass of
the sample before and after each drying step.
3.0 Definitions
3.1 Total Solids-The residue left in the vessel after evaporation of liquid from a
sample and subsequent drying in an oven at 103°C to 105°C.
3.2 Additional definitions are given in Sections 3.0 of Method 200.7.
4.0 Interferences
4.1 Sampling, subsampling, and pipeting multi-phase samples may introduce
serious errors (Reference 13.1). Make and keep such samples homogeneous
January 2001 Draft ~
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Method 200.7
during transfer. Use special handling to ensure sample integrity when
subsampling. Mix small samples with a magnetic stirrer. If visible suspended
solids are present, pipet with wide-bore pipets. If part of a sample adheres to
the sample container, intensive homogenization is required to ensure accurate
results. When dried, some samples form a crust that prevents evaporation;
special handling such as extended drying times are required to deal with this.
Avoid using a magnetic stirrer with samples containing magnetic particles.
4.2 The temperature and time of residue drying has an important bearing on results
(Reference 1). Problems such as weight losses due to volatilization of organic
matter, and evolution of gases from heat-induced chemical decomposition,
weight gains due to oxidation, and confounding factors like mechanical occlusion
of water and water of crystallization depend on temperature and time of heating.
It is therefore essential that samples be dried at a uniform temperature, and for
no longer than specified. Each sample requires close attention to desiccation
after drying. Minimize the time the desiccator is open because moist air may
enter and be absorbed by the samples. Some samples may be stronger
desiccants than those used in the desiccator and may take on water.
4.3 Residues dried at 103°C to 105°C may retain some bound water as water of
crystallization or as water occluded in the interstices of crystals. They lose C02
in the conversion of bicarbonate to carbonate. The residues usually lose only
slight amounts of organic matter by volatilization at this temperature. Because
removal of occluded water is marginal at this temperature, attainment of constant
weight may be very slow.
4.4 Results for residues high in oil or grease may be questionable because of the
difficulty of drying to constant weight in a reasonable time.
4.5 The determination of total solids is subject to negative error due to loss of
ammonium carbonate and volatile organic matter during the drying step at
103°C to 105°C. Carefully observe specified ignition time and temperature to
control losses of volatile inorganic salts if these are a problem.
5.0 Safety
5.1 Refer to Section 5.0 of Method 200.7 for safety precautions.
6.0 Equipment and Supplies
NOTE: Brand names, suppliers, and part numbers are cited for illustrative purposes only. No
endorsement is implied. Equivalent performance may be achieved using equipment and
materials other than those specified here, but demonstration of equivalent performance that
meets the requirements of this method is the responsibility of the laboratory.
Draft January2001
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Method 200.7
6.1 Evaporating Dishes-Dishes of 100-mL capacity. The dishes may be made of
porcelain (90-mm diameter), platinum, or high-silica glass.
6.2 Watch glass-Capable of covering the evaporating dishes (Section 6.1).
6.3 Steam bath.
6.4 Desiccator-Moisture concentration in the desiccator should be monitored by an
instrumental indicator or with a color-indicator desiccant.
6.5 Drying oven-Thermostatically-controlled, capable of maintaining a uniform
temperature of 103°C to 105°C throughout the drying chamber.
6.6 Analytical balance-Capable of weighing to 0.1 mg for samples having a mass up
to 200 g.
6.7 Container handling apparatus-Gloves, tongs, or a suitable holder for moving
and handling hot containers after drying.
6.8 Bottles-Glass or plastic bottles of a suitable size for sample collection.
6.9 Rubber gloves (Optional).
6.10 No. 7 Cork borer (Optional).
7.0 Reagents and Standards
7.1 Reagent water-Deionized, distilled, or otherwise purified water.
7.2 Sodium chloride-potassium hydrogen phthalate standard (NaCI-KHP).
7.2.1 Dissolve 0.10 g sodium chloride (NaCI) in 500 ml reagent water. Mix to
dissolve.
7.2.2 Add 0.10 g potassium hydrogen phthalate (KHP) to the NaCI solution
(Section 7.2.1) and mix. If the KHP does not dissolve readily, warm the
solution while mixing. Dilute to 1 L with reagent water. Store at 4°C.
Assuming 100% volatility of the acid phthalate ion, this solution contains
200 mg/L total solids, 81.0 mg/L volatile solids, and 119 mg/L fixed solids.
8.0 Sample Collection, Preservation, and Storage
8.1 Use resistant-glass or plastic bottles to collect sample for solids analysis,
provided that the material in suspension does not adhere to container walls.
Sampling should be done in accordance with Reference 13.2. Begin analysis as
soon as possible after collection because of the impracticality of preserving the
January 2001 Draft ~
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Method 200.7
sample. Refrigerate the sample at 4°C up to the time of analysis to minimize
microbiological decomposition of solids. Preferably do not hold samples more
than 24 hours. Under no circumstances should the sample be held more than
seven days. Bring samples to room temperature before analysis.
9.0 Quality Control
9.1 Quality control requirements and requirements for performance-based methods
are given in Section 9.1 of Method 200.7.
9.2 Initial demonstration of laboratory capability - The initial demonstration of
laboratory capability is used to characterize laboratory performance and method
detection limits.
9.2.1 Method detection limit (MDL) - The method detection limit should be
established for the analyte, using diluted NaCI-KHP standard (Section
7.2). To determine MDL values, take seven replicate aliquots of the
diluted NaCI-KHP solution and process each aliquot through each step of
the analytical method. Perform all calculations and report the
concentration values in the appropriate units. MDLs should be determined
every year or whenever a modification to the method or analytical system
is made that will affect the method detection limit.
9.2.2 Initial Precision and Recovery (IPR) - To establish the ability to generate
acceptable precision and accuracy, the analyst shall perform the following
operations:
9.2.2.1 Prepare four samples by diluting NaCI-KHP standard
(Section 7.2) to 1-5 times the MDL. Using the procedures in
Section 11, analyze these samples for total solids.
9.2.2.2 Using the results of the four analyses, compute the average
percent recovery (x) and the standard deviation (s, Equation
1) of the percent recovery for total solids.
Equation 1
.=
n- l
Where:
n = number of samples
x = % recovery in each sample
s = standard deviation
A-4 Draft January 2001
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Method 200.7
9.2.2.3 Compare s and x with the corresponding limits for initial
precision and recovery in Table 2 (to be determined in
validation study). If s and x meet the acceptance criteria,
system performance is acceptable and analysis of samples
may begin. If, however, s exceeds the precision limit or x
falls outside the range for recovery, system performance is
unacceptable. In this event, correct the problem, and repeat
the test.
9.3 Laboratory blanks
9.3.1 Prepare and analyze a laboratory blank initially (i.e. with the tests in
Section 9.2) and with each analytical batch. The blank must be subjected
to the same procedural steps as a sample, and will consist of
approximately 25 g of reagent water.
9.3.2 If material is detected in the blank at a concentration greater than the
MDL (Section 1.3), analysis of samples must be halted until the source of
contamination is eliminated and a new blank shows no evidence of
contamination. All samples must be associated with an uncontaminated
laboratory blank before the results may be reported for regulatory compli-
ance purposes.
9.4 Ongoing Precision and Recovery
9.4.1 Prepare an ongoing precision and recovery (OPR) solution identical to
the IPR solution described in Section 9.2.2.1.
9.4.2 An aliquot of the OPR solution must be analyzed with each sample batch
(samples started through the sample preparation process (Section 11) on
the same 12-hour shift, to a maximum of 20 samples).
9.4.3 Compute the percent recovery of total solids in the OPR sample.
9.4.4 Compare the results to the limits for ongoing recovery in Table 2 (to be
determined in validation study). If the results meet the acceptance criteria,
system performance is acceptable and analysis of blanks and samples
may proceed. If, however, the recovery of total solids falls outside of the
range given, the analytical processes are not being performed properly.
Correct the problem, reprepare the sample batch, and repeat the OPR
test. All samples must be associated with an OPR analysis that passes
acceptance criteria before the sample results can be reported for
regulatory compliance purposes.
9.4.5 results that pass the specifications in Section 9.4.4 to IPR and previous
OPR data. Update QC charts to form a graphic representation of
continued laboratory performance. Develop a statement of laboratory
January 2001 Draft ~
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Method 200.7
accuracy for each analyte by calculating the average percent recovery (R)
and the standard deviation of percent recovery (SR). Express the
accuracy as a recovery interval from R-2SR to R+2SR. For example, if
R=05% and SR=5%, the accuracy is 85-115%.
9.5 Duplicate analyses
9.5.1 Ten percent of samples must be analyzed in duplicate. The duplicate
analyses must be performed within the same sample batch (samples
whose analysis is started within the same 12-hour period, to a maximum
of 20 samples).
9.5.2 The total solids of the duplicate samples must be within 10%.
10.0 Calibration and Standardization
10.1 Calibrate the analytical balance at 2 mg and 1000 mg using class "S" weights.
10.2 Calibration shall be within ± 10% (i.e. ±0.2 mg) at 2 mg and ± 0.5% (i.e. ±5 mg)
at 1000 mg. If values are not within these limits, recalibrate the balance.
11.0 Procedure
11.1 Preparation of evaporating dishes-Heat dishes and watch glasses at 103°C to
105°C for 1 hour in an oven. Cool and store the dried equipment in a
desiccator. Weigh each dish and watch glass prior to use (record combined
weight as "Wdish").
11.2 Preparation of samples
11.2.1 Fluid samples-lf the sample contains enough moisture to flow readily, stir
to homogenize, place a 25 to 50 g sample aliquot on the prepared
evaporating dish. If the sample is to be analyzed in duplicate, the mass of
the two aliquots may not differ by more than 10%. Spread each sample
so that it is evenly distributed over the evaporating dish. Evaporate the
samples to dryness on a steam bath. Cover each sample with a watch
glass, and weigh (record weight as "Wsampte").
NOTE: Weigh wet samples quickly because wet samples tend to lose weight by evaporation.
Samples should be weighed immediately after aliquots are prepared.
11.2.2 Solid samples-lf the sample consists of discrete pieces of solid material
(dewatered sludge, for example), take cores from each piece with a No. 7
cork borer or pulverize the entire sample coarsely on a clean surface by
hand, using rubber gloves. Place a 25 to 50 g sample aliquot of the
pulverized sample on the prepared evaporating dish. If the sample is to
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Method 200.7
be analyzed in duplicate, the mass of the two aliquots may not differ by
more than 10%. Spread each sample so that it is evenly distributed over
the evaporating dish. Cover each sample with a watch glass, and weigh
(record weight as "Wsample").
11.3 Dry the samples at 103°C to 105°C for a minimum of 12 hours, cool to balance
temperature in an individual desiccator containing fresh desiccant, and weigh.
Heat the residue again for 1 hour, cool it to balance temperature in a desiccator,
and weigh. Repeat this heating, cooling, desiccating, and weighing procedure
until the weight change is less than 5% or 50 mg, whichever is less. Record the
final weight as "Wtotal."
NOTE: It is imperative that dried samples weighed quickly since residues often are very
hygroscopic and rapidly absorb moisture from the air. Samples must remain in the dessicator
until the analyst is ready to weigh them.
12.0 Data Analysis and Calculations
12.1 Calculate the % solids or the mg solids/kg sludge for total solids (Equation 2).
Equation 2
% total solids = —^ — * 100
"sample ~ "dish
or
mg total solids W. ., - W,.,
— = —^ ^-* 1 000 000
kg sludge Wsample - Wdish
Where:
Wdjsh=Weight of dish (mg)
Wsample=Weight of wet sample and dish (mg)
W^fal=Weight of dried residue and dish (mg)
12.2 Sample results should be reported as % solids or mg/kg to three significant
figures. Report results below the ML as < the ML, or as required by the
permitting authority or in the permit.
13.0 Method Performance
13.1 Method performance (MDL and quality control acceptance criteria) will be
determined during the multi-lab validation of this method.
13.2 Total solids duplicate determinations must agree within 10% to be reported for
permitting purposes. If duplicate samples do not meet this criteria, the problem
must be discovered and the sample must be run over.
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Method 200.7
14.0 Pollution Prevention
14.2 Pollution prevention details are given in Section 14 of Method 200.7.
15.0 Waste Management
15.1 Waste management details are given in Section 15 of Method 200.7.
16.0 References
16.1 "Standard Methods for the Examination of Water and Wastewater," 18th ed. and
later revisions, American Public Health Association, 1015 15th Street NW,
Washington, DC 20005. 1-35: Section 1090 (Safety), 1992.
16.2 U.S. Environmental Protection Agency, 1992. Control of Pathogens and Vector
Attraction in Sewage Sludge. Publ 625/R-92/013. Office of Research and
Development, Washington, DC.
17.0 Tables, Diagrams, Flowcharts, and Validation Data
17.1 Tables containing method requirements for QA/QC will be added after the
validation study has been performed.
Draft January 2001
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