EPA-821-R-01-006
January 2001
Method 1632
Chemical Speciation of Arsenic in Water and Tissue by Hydride
Generation Quartz Furnace Atomic Absorption Spectrometry
Revision A
January 2001
U.S. Environmental Protection Agency
Office of Water
Engineering and Analysis Division (4303)
Ariel Rios Building
1200 Pennsylvania Avenue, NW
Washington, B.C. 20460
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Method 163 2
Acknowledgments
Method 1632 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). The method was
prepared under EPA Contract 68-C3-0337 by the DynCorp Environmental Programs Division with
assistance from Quality Works, Inc. and Interface, Inc. The method is based on procedures developed by
Eric Crecelius of the Battelle Marine Sciences Laboratory in Sequim, Washington.
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. This method
version contains minor editorial changes to the September 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
Engineering and Analysis Division (4303)
U.S. Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460
Phone: 202/260-7134
Fax: 202/260-7185
Draft, January 2001
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Method 163 2
Introduction
This analytical method supports water quality monitoring programs authorized under the Clean Water Act
(CWA, the "Act"). CWA Section 304(a) requires EPA to publish water quality criteria that reflect the
latest scientific knowledge concerning the physical fate (e.g., concentration and dispersal) of pollutants, the
effects of pollutants on ecological and human health, and the effect of pollutants on biological community
diversity, productivity, and stability.
CWA Section 303 requires each State to set a water quality standard for each body of water within its
boundaries. A State water quality standard consists of a designated use or uses of a water body or a
segment of a water body, the water quality criteria that are necessary to protect the designated use or uses,
and an anti-degradation policy. These water quality standards serve two purposes: (1) they establish the
water quality goals for a specific water body, and (2) they are the basis for establishing water quality-based
treatment controls and strategies beyond the technology-based controls required by CWA Sections 301(b)
and 306.
In defining water quality standards, a State may use narrative criteria, numeric criteria, or both. However,
the 1987 amendments to CWA required States to adopt numeric criteria for toxic pollutants (designated in
Section 307(a) of the Act) based on EPA Section 304(a) criteria or other scientific data, when the discharge
or presence of those toxic pollutants could reasonably be expected to interfere with designated uses.
In some cases, these water quality criteria (WQC) are as much as 280 times lower than levels measurable
using approved EPA methods and required to support technology-based permits. EPA developed new
sampling and analysis methods to specifically address State needs for measuring toxic metals at WQC
levels, when such measurements are necessary to protect designated uses in State water quality standards.
The latest criteria published by EPA are those listed in the National Toxics Rule (58 FR 60848) and the
Stay of Federal Water Quality Criteria for Metals (60 FR 22228). These rules include WQC for 13
metals, and it is these criteria on which the new sampling and analysis methods are based. Method 1632
was specifically developed to provide reliable measurements of inorganic arsenic at EPA WQC levels using
hydride generation quartz furnace atomic absorption techniques. It has since been modified to include
determination of arsenic species.
In developing methods for determination of trace metals, EPA found that one of the greatest difficulties was
precluding sample contamination during collection, transport, and analysis. The degree of difficulty,
however, is highly dependent on the metal and site-specific conditions. This method is designed to preclude
contamination in nearly all situations. It also contains procedures necessary to produce reliable results at
the lowest WQC levels published by EPA. In recognition of the variety of situations to which this Method
may be applied, and in recognition of continuing technological advances, Method 1632 is performance
based. Alternative procedures may be used so long as those procedures are demonstrated to yield reliable
results.
Requests for additional copies of this publication should be directed to:
U.S. EPANCEPI
P.O. Box 42419
Cincinnati, OH 45242
1-800-490-9198
Fax: (513)489-8695
http://www.epa.gov/ncepihom/
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Method 163 2
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 tests. The terms "shall," "must," and "may not" define
procedures required for producing reliable data at water quality criteria levels. 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.
Draft, January 2001
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Method 1632
Chemical Speciation of Arsenic in Water and Tissue by Hydride Generation
Quartz Furnace Atomic Absorption Spectrometry
1.0 Scope and Application
1 . 1 This method is for determination of inorganic arsenic (IA), arsenite (As+3), arsenate (As+5),
monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in filtered and unfiltered water and
in tissue by hydride generation and quartz furnace atomic absorption detection. The method is for use
in EPA's data gathering and monitoring programs associated with the Clean Water Act. The method
is based on a contractor-developed method (Reference 16.1) and on peer-reviewed, published
procedures for the speciation of As in aqueous samples (Reference 16.2).
1 .2 This method is accompanied by Method 1669: Sampling Ambient Water for Trace Metals at EPA
Water Quality Criteria Levels (the Sampling Guidance). The Sampling Guidance may be necessary
to preclude contamination during the sampling process.
1 .3 This method is designed for measurement of As species in water in the range 0.01-50 Aig/L and in
tissue in the range 0. 10-500 jWg/g dry weight. This method may be applicable to determination of
arsenic species in industrial discharges after sample dilution. Existing regulations (40 CFR parts 400-
500) typically limit concentrations in industrial discharges to the part-per-billion (ppb) range, whereas
ambient As concentrations are normally in the low part-per-trillion (ppt) to low part-per-billion range.
1 .4 The method detection limits and minimum levels of quantitation in this method are usually dependent
on the level of background elements and interferences rather than instrumental limitations. Table 1
lists method detection limits (MDLs) and minimum levels of quantitation (MLs) in water when no
background elements or interferences are present as determined by two laboratories. Table 1 also
shows MDLs and MLs in a reference tissue matrix (corn oil).
1 .5 The ease of contaminating water samples with As and interfering substances cannot be
overemphasized. This method includes suggestions for improvements in facilities and analytical
techniques that should maximize the ability of the laboratory to make reliable trace metals
determinations and minimize contamination (Section 4.0). Additional suggestions for improvement of
existing facilities may be found in EPA's Guidance on Establishing Trace Metals Clean Rooms in
Existing Facilities, which is available from the National Center for Environmental Publications and
Information (NCEPI) at the address listed in the introduction to this document.
1 .6 Clean and ultra clean — The terms "clean" and "ultra clean" have been applied to the techniques needed
to reduce or eliminate contamination in trace metals determinations. These terms are not used in this
method because they lack an exact definition. However, the information provided in this method is
consistent with EPA's summary guidance on clean and ultra clean techniques.
1 .7 This method follows the EPA Environmental Methods Management Council's "Format for Method
Documentation."
1 .8 This method is "performance based." The laboratory is permitted to modify the method to overcome
interferences or lower the cost of measurements if all performance criteria are met. Section 9.1.2
gives the requirements for establishing method equivalency.
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Method 163 2
1.9 Any modification of this method, beyond those expressly permitted, shall be considered a major
modification subject to application and approval of alternate test procedures at 40 CFR 136.4 and
136.5.
1.10 Each laboratory that uses this method must demonstrate the ability to generate acceptable results
(Section 9.2).
1.11 This method is accompanied by a data verification and validation guidance document, Guidance
on the Documentation and Evaluation of Trace Metals Data Collected for CWA Compliance
Monitoring. This guidance document may be useful for reviewing data collected using this
method.
2.0 Summary of Method
2.1 Aqueous sample—A 500- to 1000-mL water sample is collected directly into a cleaned fluoropolymer,
conventional or linear polyethylene, polycarbonate, or polypropylene sample bottle using sample
handling techniques specially designed for collection of metals at trace levels (Reference 16.3). Water
samples are preserved in the field by the addition of 3 mL of pretested 6M HC1 per liter of sample.
The recommended holding time is 28 days.
2.2 Tissue sample—A 10- to 50-g wet weight sample is collected into a glass or fluoropolymer,
conventional or linear polyethylene, polycarbonate, or polypropylene sample bottle, also using sample
handling techniques specially designed for collection of metals at trace levels. The tissue sample is
either freeze-dried and stored at room temperature or stored frozen at less than -18 °C. Prior to
analysis, tissue samples are digested in HC1 or NaOH at 80 °C for 16 hours. Matrix spike recoveries
indicate that As+3 is more stable in HC1 than NaOH.
2.3 An aliquot of water sample or tissue digestate is placed in a specially designed reaction vessel, and 6M
HC1 is added.
2.4 Four percent NaBH4 solution is added to convert IA, MMA, and DMA to volatile arsines.
2.5 Arsines are purged from the sample onto a cooled glass trap packed with 15% OV-3 on Chromosorb®
W AW-DMCS, or equivalent.
2.6 The trapped arsines are thermally desorbed, in order of increasing boiling points, into an inert gas
stream that carries them into the quartz furnace of an atomic absorption spectrophotometer for
detection. The first arsine to be desorbed is AsH3, which represents IA in the sample. MMA and
DMA are desorbed and detected several minutes after the first arsine.
2.7 Quality is ensured through calibration and testing of the hydride generation, purging, and detection
systems.
2.8 To determine the concentration of As+3, another aliquot of water sample or tissue digestate is placed in
the reaction vessel and Tris-buffer is added. The procedure in Sections 2.4 through 2.7 is repeated to
quantify only the arsine produced from As+3.
2.9 The concentration of As+5 is the concentration of As+3 subtracted from the concentration of IA.
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Method 163 2
3.0 Definitions
3.1 Apparatus—Throughout this method, the sample containers, sampling devices, instrumentation, and
all other materials and devices used in sample collection, sample processing, and sample analysis that
come in contact with the sample and therefore require careful cleaning will be referred to collectively
as the Apparatus.
3.2 Dissolved Inorganic Arsenic—All NaBH4-reducible As+3 and As+5 found in aqueous solution filtrate
after passing the sample through a 0.45 pn capsule filter.
3.3 Total Inorganic Arsenic—All NaBH4-reducible As+3 and As+5 found in a sample. In this method, total
inorganic arsenic and total recoverable inorganic arsenic are synonymous.
3.4 Definitions of other terms used in this method are given in the glossary at the end of the method.
4.0 Contamination and Interferences
4.1 Preventing ambient water samples from becoming contaminated during the sampling and analytical
processes constitutes one of the greatest difficulties encountered in trace metal determinations. Over
the last two decades, marine chemists have come to recognize that much of the historical data on the
concentrations of dissolved trace metals in seawater are erroneously high because the concentrations
reflect contamination from sampling and analysis rather than ambient levels. Therefore, it is
imperative that extreme care be taken to avoid contamination when collecting and analyzing ambient
water samples for As species at trace levels.
4.2 Samples may become contaminated by numerous routes. Potential sources of trace metal
contamination during sampling include: metallic or metal-containing labware, containers, sampling
equipment, reagents, and reagent water; improperly cleaned and stored equipment, labware, and
reagents; and atmospheric inputs such as dirt and dust. Even human contact can be a source of trace
metal contamination.
4.3 Contamination Control
4.3.1 Philosophy—The philosophy behind contamination control is to ensure that any object or
substance that contacts the sample is arsenic-free and free from any material that may
contain As, As species, or material that might interfere with the analysis of samples.
4.3.1.1 The integrity of the results produced must not be compromised by contamination of
samples. This method and the Sampling Method give requirements and suggestions for
control of sample contamination.
4.3.1.2 Substances in a sample cannot be allowed to contaminate the laboratory work area or
instrumentation used for trace metal measurements. This method gives requirements
and suggestions for protecting the laboratory.
4.3.1.3 Although contamination control is essential, personnel health and safety remain the
highest priority. The Sampling Method and Section 5.0 of this method give
requirements and suggestions for personnel safety.
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Method 163 2
4.3.2 Avoiding contamination—The best way to control contamination is to completely avoid
exposure of the sample to contamination in the first place. Avoiding exposure means
performing operations in an area known to be free from contamination. Two of the most
important factors in avoiding/reducing sample contamination are (1) an awareness of
potential sources of contamination and (2) strict attention to the work being done.
Therefore, it is imperative that the procedures described in this method be carried out by
well-trained, experienced personnel.
4.3.3 Use a clean environment—The ideal environment for processing samples is a class 100
clean room (Section 1.5). If a clean room is not available, all sample preparation should be
performed in a class 100 clean bench or a nonmetal glove box fed by arsenic- and particle-
free air or nitrogen. Digestions should be performed in a nonmetal fume hood situated,
ideally, in the clean room.
4.3.4 Minimize exposure—Any apparatus that will contact samples, blanks, or standard solutions
should be opened or exposed only in a clean room, clean bench, or glove box so that
exposure to an uncontrolled atmosphere is minimized. When not in use, the apparatus
should be covered with clean plastic wrap and stored in the clean bench, in a plastic box, or
in a glove box, or bagged in clean zip-type bags. Minimizing the time between cleaning and
use will also minimize contamination.
4.3.5 Clean work surfaces—Before a given batch of samples is processed, all work surfaces in the
hood, clean bench, or glove box in which the samples will be processed should be cleaned by
wiping with a lint-free cloth or wipe soaked with reagent water.
4.3.6 Wear gloves—Sampling personnel must wear clean, non-talc gloves during all operations
involving handling of the apparatus, samples, and blanks. Only clean gloves may touch the
apparatus. If another object or substance is touched, the glove(s) must be changed before
again handling the apparatus. If it is even suspected that gloves have become contaminated,
work must be halted, the contaminated gloves removed, and a new pair of clean gloves put
on. Wearing multiple layers of clean gloves will allow the old pair to be quickly stripped
with minimal disruption to the work activity.
4.3.7 Use metal-free apparatus—All apparatus used for determination of As and/or As species at
ambient water quality criteria levels must be nonmetallic and free of material that may
contain metals.
4.3.7.1 Construction materials—Only fluoropolymer (FEP, PTFE), conventional or linear
polyethylene, polycarbonate, or polypropylene containers should be used for samples
that will be analyzed for As. PTFE is less desirable than FEP because the sintered
material in PTFE may contain contaminants and is susceptible to serious memory
effects (Reference 16.4). All materials, regardless of construction, that will directly or
indirectly contact the sample must be cleaned using the procedures given (Section
6.1.2) and must be known to be clean and arsenic-free before proceeding.
Note: Glass containers may be used for tissue sample collection.
4.3.7.2 Serialization—It is recommended that serial numbers be indelibly marked or etched on
each piece of apparatus so that contamination can be traced. Logbooks should be
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Method 163 2
maintained to track the sample from the container through the labware to injection into
the instrument. It may be useful to dedicate separate sets of labware to different
sample types; e.g., receiving waters and effluents. However, the apparatus used for
processing blanks and standards must be mixed with the apparatus used to process
samples so that contamination of all labware can be detected.
4.3.7.3 The laboratory or cleaning facility is responsible for cleaning the apparatus used by the
sampling team. If there are any indications that the apparatus is not clean when
received by the sampling team (e.g., ripped storage bags), an assessment of the
likelihood of contamination must be made. Sampling must not proceed if it is possible
that the apparatus is contaminated. If the apparatus is contaminated, it must be
returned to the laboratory or cleaning facility for proper cleaning before it is used in
any sampling activity.
4.3.8 Avoid sources of contamination—Avoid contamination by being aware of potential sources
and routes of contamination.
4.3.8.1 Contamination by carryover—Contamination may occur when a sample containing low
concentrations of As is processed immediately after a sample containing relatively high
concentrations of As. To reduce carryover, the sample introduction system may be
rinsed between samples with dilute acid and reagent water. When an unusually
concentrated sample is encountered, it should be followed by analysis of a method
blank to check for carryover. Samples known or suspected to contain the lowest
concentration of As should be analyzed first followed by samples containing higher
levels.
4.3.8.2 Contamination by samples—Significant laboratory or instrument contamination may
result when untreated effluents, in-process waters, landfill leachates, and other samples
containing high concentrations of As are processed and analyzed. This method is not
intended for application to these samples, and samples containing high concentrations
should not be permitted into the clean room and laboratory dedicated for processing
trace metal samples.
4.3.8.3 Contamination by indirect contact—Apparatus that does not directly come in contact
with the samples may still be a source of contamination. For example, clean tubing
placed in a dirty plastic bag may pick up contamination from the bag and subsequently
transfer the contamination to the sample. Therefore, it is imperative that every piece of
the apparatus that is directly or indirectly used in the collection, processing, and
analysis of water and tissue samples be thoroughly cleaned (see Section 6.1.2).
4.3.8.4 Contamination by airborne particulate matter—Less obvious substances capable of
contaminating samples include airborne particles. Samples may be contaminated by
airborne dust, dirt, particles, or vapors from unfiltered air supplies; nearby corroded or
rusted pipes, wires, or other fixtures; or metal-containing paint. Whenever possible,
sample processing and analysis should occur as far as possible from sources of
airborne contamination.
4.4 Interferences—Water vapor may condense in the transfer line between the cold trap and the atomizer
if it is not well heated. Such condensation can interfere with the determination of DMA.
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Method 163 2
5.0 Safety
5.1 The toxicity or carcinogenicity of each chemical used in this method has not been precisely
determined; however, each compound should be treated as a potential health hazard. Exposure to
these compounds should be reduced to the lowest possible level. It is recommended that the laboratory
purchase a dilute standard solution of the As and/or As species to be used in this method. If solutions
are prepared from pure solids, they shall be prepared in a hood, and a NIOSH/MESA-approved toxic
gas respirator shall be worn when high concentrations are handled.
5.2 This method does not address all safety issues associated with its use. The laboratory is responsible
for maintaining a current awareness file of OSHA regulations for the safe handling of the chemicals
specified in this method. A reference file of material safety data sheets (MSDSs) should also be made
available to all personnel involved in these analyses. It is also suggested that the laboratory perform
personal hygiene monitoring of each analyst who uses this method and that the results of this
monitoring be made available to the analyst. Additional information on laboratory safety can be found
in References 16.5-16.8.
5.3 Samples suspected to contain high concentrations of As and/or As species are handled using
essentially the same techniques used in handling radioactive or infectious materials. Well-ventilated,
controlled access laboratories are required. Assistance in evaluating the health hazards of particular
laboratory conditions may be obtained from certain consulting laboratories and from State
Departments of Health or Labor, many of which have an industrial health service. Each laboratory
must develop a strict safety program for handling As and/or As species.
5.3.1 Facility—When samples known or suspected of containing high concentrations (> 50 (jg/Lor
>500(jg/g) of total As are handled, all operations (including removal of samples from
sample containers, weighing, transferring, and mixing) should be performed in a glove box
demonstrated to be leak tight or in a fume hood demonstrated to have adequate air flow.
Gross losses to the laboratory ventilation system must not be allowed. Handling of the
dilute solutions normally used in analytical and animal work presents no inhalation hazards
except in an accident.
5.3.2 Protective equipment—Disposable plastic gloves, apron or laboratory coat, safety glasses or
mask, and a glove box or fume hood adequate for radioactive work should be used when
handling arsenic powders. During analytical operations that may give rise to aerosols or
dusts, personnel should wear respirators equipped with activated carbon filters.
5.3.3 Training—Workers must be trained in the proper method of removing contaminated gloves
and clothing without contacting the exterior surfaces.
5.3.4 Personal hygiene—Hands and forearms should be washed thoroughly after each
manipulation and before breaks (including coffee, lunch, and shift).
5.3.5 Confinement—Isolated work areas posted with signs, with their own segregated glassware
and tools, and with plastic absorbent paper on bench tops will aid in confining
contamination.
5.3.6 Effluent vapors—The effluent vapors from the atomic absorption spectrophotometer (AAS)
should pass through either a column of activated charcoal or a trap designed to remove As
and/or As species.
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Method 163 2
5.3.7 Waste handling—Good waste handling techniques include minimizing contaminated waste.
Plastic bag liners should be used in waste cans. Janitors and other personnel must be trained
in the safe handling of waste.
5.3.8 Decontamination
5.3.8.1 Decontamination of personnel—Use any mild soap with plenty of scrubbing action.
5.3.8.2 Glassware, tools, and surfaces—Satisfactory cleaning may be accomplished by
washing with any detergent and water.
5.3.9 Laundry—Clothing known to be contaminated should be collected in plastic bags. Persons
who convey the bags and launder the clothing should be advised of the hazard and trained in
proper handling. If the launderer knows of the potential problem, the clothing may be put
into a washing machine without contact. The washing machine should be run through a full
cycle before being used for other clothing.
6.0 Apparatus and Materials
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
Environmental Protection Agency. Equivalent performance may be achievable using apparatus,
materials, or cleaning procedures other than those suggested here. The laboratory is responsible
for demonstrating equivalent performance.
6.1 Sampling Equipment
6.1.1 Sample collection bottles—Fluoropolymer, conventional or linear polyethylene,
polycarbonate, or polypropylene, 500-1000 mL for aqueous samples. Glass or plastic
(fluoropolymer, etc.) jars for tissue samples.
6.1.2 Cleaning—Sample collection bottles, glass jars, and glass vials are cleaned with liquid
detergent and thoroughly rinsed with reagent water. The bottles are then immersed in IN
trace metal grade HC1 for at least 48 hours. The bottles are thoroughly rinsed with reagent
water, air dried in a class 100 area, and double-bagged in new polyethylene zip-type bags
until needed.
NOTE: Plastic sample bottles should not be cleaned with HNO3 as it oxidizes chemicals that may
remain in the plastic.
6.1.3 Tissue digestion vials— Glass scintillation vials (25-mL) with fluoropolymer-lined lids are
used for the digestion of tissue samples.
6.2 Equipment for bottle and glassware cleaning.
6.2.1 Vats—Up to 200-L capacity, constructed of high-density polyethylene (HOPE) or other
nonmetallic, non-contaminating material suitable for holding dilute HC1.
6.2.2 Laboratory sink—In Class 100 clean area, with high-flow reagent water for rinsing.
6.2.3 Clean bench—Class 100, for drying rinsed bottles.
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Method 163 2
6.3 Atomic absorption spectrophotometer (AAS)—Any AAS may serve as a detector. A bracket is
required to hold the quartz atomizer in the optical path of the instrument. Table 3 gives typical
conditions for the spectrophotometer.
6.3.1 Electrodeless discharge lamp—For measuring As at 193.7 nm.
6.3.2 Quartz cuvette burner tube (Reference 16.2)—70 mm long and 9 mm in diameter with two 6
mm O.D. side tubes, each 25 mm long. Figure 1A shows a schematic diagram of the tube
and bracket.
6.4 Reaction vessel—Figure IB shows the schematic diagram for the vessel used for the reaction of the
sample with sodium borohydride. The system consists of the following:
6.4.1 125-mL gas wash bottle—Corning # 1760-125, or equivalent, onto which an 8 mm O.D.
sidearm inlet tube 2 cm long has been grafted. A smaller reaction vessel (30-mL size) can
be used for up to 5 mL aqueous samples and tissue digestates.
6.4.2 Silicone rubber stopper septum—Ace Glass #9096-32, or equivalent.
6.4.3 Four-way fluoropolymer stopcock valve—Capable of switching the helium from the purge
to the analysis mode of operation.
6.4.4 Flow meter/needle valve—Capable of controlling and measuring gas flow rate to the
reaction vessel at 150 (±30) mL/minute.
6.4.5 Silicone tubing—All glass-to-glass connections are made with silicone rubber sleeves.
6.5 Cryogenic trap—Figure 1C shows the schematic diagram for the trap. It consists of the following:
6.5.1 Nichrome wire (22-gauge).
6.5.2 Variacs for controlling Nichrome wire.
6.5.3 A 6 mm O.D. borosilicate glass U-tube about 30 cm long with a 2 cm radius of bend (or
similar dimensions to fit into a tall wide mouth Dewar flask), which has been silanized and
packed halfway with 15% OV-3 on Chromosorb® W AW DMCS (45-60 mesh), or
equivalent. The ends of the tube are packed with silanized glass wool.
6.5.3.1 Conditioning the trap—The input side of the trap (the side that is not packed) is
connected with silicone rubber tubing to He at a flow rate of 40 mL/min, and the trap is
placed in an oven at 175°C for two hours. At the end of this time, two 25 i\L aliquots
of GC column conditioner (Silyl-8®, Supelco, Inc., or equivalent) are injected through
the silicone tubing into the glass trap. The trap is returned to the oven, with the He still
flowing, for 24 hours.
6.5.3.2 After conditioning, the trap is wrapped with approximately 1.8 m of 22-gauge
Nichrome wire, the ends of which are affixed to crimp-on electrical contacts.
6.5.3.3 The trap is connected by silicone rubber tubing to the output of the reaction vessel.
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Method 163 2
The output side of the trap is connected by 6 mm O.D. borosilicate tubing that has been
wrapped by Nichrome wire to the input of the flame atomizer.
6.5.4 Dewar flask—Capable of containing the trap described in Section 6.5.3.
6.6 Recorder/integrator—Any integrator with a range compatible with the AAS is acceptable.
6.7 Pipettors—All-plastic pneumatic fixed volume and variable pipettors in the range of 10 i\L to 5.0 mL.
6.8 Analytical balance—Capable of weighing to the nearest 0.01 g.
7.0 Reagents and Standards
7.1 River/reagent Water—Water demonstrated to be free from As species at the MDL as well as
potentially interfering substances. The water can be prepared by distillation or collected from the field
and filtered through a 0.2 ^m filter. It has been observed that deionized water can have an oxidizing
potential that diminishes As+3 response (References 16.1,16.2, and 16.9).
7.2 Hydrochloric acid—Trace-metal grade, purified, concentrated, reagent-grade HC1.
7.2.1 6M hydrochloric acid—Equal volumes of trace metal grade concentrated HC1 (Section 7.2)
and river/reagent water (Section 7.1) are combined to give a solution approximately 6M in
HC1.
7.2.2 2M hydrochloric acid—Trace metal grade concentrated HC1 (Section 7.2) and river/reagent
water (Section 7.1) are combined in a 1:6 ratio to give a solution approximately 2M in HC1.
7.3 Tris buffer—394 g of Tris-HCl (tris(hydroxymethyl)aminomethane hydrochloride) and 2.5 g of
reagent grade NaOH (sodium hydroxide) are dissolved in river/reagent water (Section 7.1) to make 1.0
L of a solution that is 2.5 M tris-HCl and 2.475 M HC1.
7.4 Sodium hydroxide — Reagent grade NaOH.
7.4.1 2M NaOH—Add 80 g of reagent grade NaOH to a 1 -L flask. Add about 700 mL of
river/reagent water. After the solid dissolves, dilute to 1 L to give a 2M NaOH solution.
7.4.2 0.02M NaOH—Add 10.0 mL of 2M NaOH (Section 7.4.1) to a 1-L flask. Dilute to 1 L
with river/reagent water to give a 0.02M NaOH solution.
7.5 Sodium borohydride solution (NaBH4)—Four grams of > 98% NaBH4 (previously analyzed and
shown to be free of measurable As) are dissolved in 100 mL of 0.02 M NaOH solution. This solution
is stable for only 8-10 hours, and must be made daily.
7.6 Liquid nitrogen (LN2)—For cooling the cryogenic trap.
7.7 Helium—Grade 4.5 (standard laboratory grade) helium.
7.8 Hydrogen—Grade 4.5 (standard laboratory grade) hydrogen.
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Method 163 2
7.9 Air—Grade 4.5 (standard laboratory grade) air.
7.10 Ascorbic acid
7.10.1 10% Ascorbic acid—Add 10 g reagent ascorbic acid to about 70 mL of river/reagent water
(Section 7.1) and swirl to dissolve. After the powder dissolves, dilute to 100 mL, producing
a solution which is stable for one year when stored at 4°C.
7.10.2 0.1% Ascorbic acid—Dilute 10 mL of 10% ascorbic acid solution to 1 L with river/reagent
water. This solution should be made as needed.
7.11 Arsenic standards—It is recommended that laboratories purchase standard solutions of 1000
mg/L and dilute them to make working standard solutions (Section 7.13.6). Sections 7.13.1
through 7.13.4 give directions for making stock solutions if a source is not readily available.
7.11.1 Arsenite (As+3) standard—A 1000 mg/L stock solution is made up by the dissolution of 1.73
g of reagent grade NaAsO2 in 1.0 L of the 0.1% ascorbic acid solution (Section 7.12.2).
This solution is stable for at least one year if kept refrigerated in an amber bottle.
7.11.2 Arsenate (As+5) standard—To prepare a 1000 mg/L stock solution, 4.16 g of reagent grade
Na2HAsO4 -7H2O are dissolved in 1.0 L of river/reagent water (Section 7.1). This stock
solution has been found to be stable for at least 10 years.
7.11.3 Monomethylarsonate (MMA) standard—To prepare a stock solution of 1000 mg/L, 3.90 g
of CH3AsO(ONa)2 -6H2O is dissolved in 1.0 L of river/reagent water (Section 7.1). This
stock solution has been found to be stable for at least 10 years.
7.11.4 Dimethylarsinate (DMA) standard—To prepare a stock solution of 1000 mg/L, 2.86 g of
reagent grade (CH3)2AsO2Na-3H2O (cacodylic acid, sodium salt) is dissolved in 1.0 L
river/reagent water (Section 7.1). This stock solution has been found to be stable for at least
10 years.
7.11.5 Working standard solution A—Prepare an intermediate solution containing 10 mg/L of As3+,
MMA and DMA combining measured aliquots of the above stock solutions (7.13.1, 7.13.3
and 7.13.4) and diluting to a measured volume with river/reagent water. Prepare a working
standard solution containing 500 Aig/L of As3+, MMA and DMA by diluting the intermediate
solution in river/reagent water.
NOTE: As3+ is used for calibrating the analytical system for inorganic arsenic (As3+ + As5+).
7.11.6 Working standard solution B—Prepare an intermediate solution containing 10 mg/L of As3+,
As5+, MMA and DMA combining measured aliquots of the above stock solutions (7.13.1
through 7.13.4) and diluting to a measured volume with river/reagent water. Prepare a
working standard solution containing 500 Aig/L of As3+,As5+, MMA and DMA by diluting
the intermediate solution in river/reagent water.
7.12 Corn oil—Reference matrix for tissue samples.
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Method 163 2
8.0 Sample Collection, Preservation, and Storage
8.1 Sample collection—Aqueous samples are collected as described in the Sampling Method (Reference
16.3). Tissue samples are collected as described in Reference 16.10.
8.2 Sample filtration—This step is not required if total IA and/or As species are the target analyte(s). For
dissolved IA and/or As species, samples and field blanks are filtered through a 0.45 (jm capsule filter
at the field site as described in the Sampling Method. If the dissolved As species are required
analytes, the water sample must be field filtered without contact to air. This can be accomplished by
using a capsule filter and exercising care during the filtration process. The extra care is necessary
because anoxic water may contain high concentrations of soluble iron and manganese that rapidly
precipitate when exposed to air. Iron and manganese hydroxy/oxides precipitates remove dissolved As
from water. After the sample is filtered, however, the concern is not as great. The samples are
preserved through acidification, and when the water is acidified these precipitates will dissolve.
8.3 Water sample preservation—Sample preservation must be performed in the field to reduce changes in
As speciation that may occur during transport and storage. Water samples are acidified to pH <2 with
hydrochloric acid (3 mL 6M HC1/L sample) and stored at 0-4° C from the time of collection until
analysis. Other preservation techniques for water and a variety of matrices have been explored
(References 16.1 and 16.11 through 16.13) but only the procedure described here is to be used. If As
species are not target analytes, the samples may be preserved upon receipt by the laboratory.
8.3.1 Wearing clean gloves, remove the cap from the sample bottle, add the volume of reagent
grade acid that will bring the pH to < 2 and recap the bottle immediately. If the bottle is
full, withdraw the necessary volume using a precleaned plastic pipette and then add the acid.
NOTE: When te sting pH, do not dip pH paper or a pH meter into the sample; remove a small
aliquot with a clean pipette and test the pH of the aliquot.
8.3.2 Store the preserved sample for a minimum of 48 hours at 0-4°C to allow the As adsorbed on
the container walls to completely dissolve in the acidified sample.
8.3.3 Sample bottles should be stored in polyethylene bags at 0-4°C until analysis.
8.3.3 The holding time for aqueous samples is 28 days from the time of collection until the time of
analysis.
8.4 Tissue sample preservation—The tissue sample must be frozen in the sampling container at less than -
18 °C or freeze-dried and stored at room temperature. The holding time for tissue samples is 2 years.
9.0 Quality Control/Quality Assurance
9.1 Each laboratory that uses this method is required to operate a formal quality assurance program
(Reference 16.3). The minimum requirements of this program consist of an initial demonstration of
laboratory capability, analysis of samples spiked with As and/or As species to evaluate and document
data quality, and analysis of standards and blanks as tests of continued performance. To determine if
the results of analyses meet the performance characteristics of the method, laboratory performance is
compared to established performance criteria.
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Method 163 2
9.1.1 The laboratory 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 laboratory is
permitted to exercise certain options to eliminate interferences or lower the costs of
measurements. These options include alternate digestion, concentration, and 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, that technique must have a specificity equal to or better than the specificity of the
techniques in the referenced method for the analytes of interest.
9.1.2.1 Each time this method is modified, the laboratory is required to repeat the procedures 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 less than or
equal to the MDL for this method or one-third the regulatory compliance level,
whichever is greater. If the change will affect calibration, the laboratory must
recalibrate the instrument according to Section 10.0 of this method.
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 metals measured (As and/or As species), by name and CAS
Registry number.
9.1.2.2.3 A narrative stating 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) Calibration (Section 10.1)
(b) Calibration verification (Section 9.5 and 10.2)
(c) Initial precision and recovery (Section 9.2.2)
(d) Analysis of blanks (Section 9.6)
(e) Matrix spike/matrix spike duplicate analysis (Section 9.3 and 9.4)
(f) Ongoing precision and recovery (Section 9.7)
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) Preparation dates
(c) Analysis dates and times
(d) Analysis sequence/run chronology
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Method 163 2
(e) Sample volume
(f) Volume before each preparation step
(g) Volume after each preparation step
(h) Final volume before analysis
(i) Dilution data
(j) Instrument and operating conditions (make, model, revision, modifications)
(k) Sample introduction system (ultrasonic nebulizer, hydride generator, flow injection
system, etc.)
(1) Operating conditions (ashing temperature, temperature program, flow rates, etc.)
(m) Detector (type, operating conditions, etc.)
(n) Printer tapes and other recordings of raw data
(o) Quantitation reports, data system outputs, and other data to link the raw data to
the results reported
9.1.3 Analyses of blanks are required to demonstrate freedom from contamination. Section 9.6
describes the required blank types and the procedures and criteria for analysis of blanks.
9.1.4 The laboratory shall spike at least 10% of the samples with As species to monitor method
performance. Section 9.3 describes this test. When results of these spikes indicate atypical
method performance, an alternate extraction or cleanup technique must be used to bring
method performance within acceptable limits. If method performance for spikes cannot be
brought within the limits given in this method, the result may not be reported or used for
permitting or regulatory compliance purposes.
9.1.5 The laboratory shall, on an ongoing basis, demonstrate through calibration verification (for
water and tissue samples) and through analysis of the ongoing precision and recovery
aliquot (for tissue samples) that the analytical system is within specified limits. Sections 9.5
and 9.7 describe these required procedures.
9.1.6 The laboratory shall maintain records to define the quality of data that are generated.
Section 9.3.4 describes the development of accuracy statements.
9.2 Initial demonstration of laboratory capability.
9.2.1 Method detection limit—To establish the ability to detect each As species, the laboratory
must determine the MDL for each analyte per 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 for each analyte that is no more than one-tenth the
regulatory compliance level or that is less than or equal to the MDL listed in Table 1,
whichever is greater.
9.2.2 Initial precision and recovery (IPR)—To establish the ability to generate acceptable
precision and recovery, the laboratory shall perform the following operations.
9.2.2.1 Analyze four aliquots of river/reagent water (Section 7.1) or corn oil (tissue reference
matrix; Section 7.14) spiked with the analyte(s) of interest at one to five times the ML
(Table 1). All sample preparation steps, and the containers, labware, and reagents that
will be used with samples must be used in this test.
9.2.2.2 Using results of the set of four analyses, compute the average percent recovery (X) of
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Method 163 2
each analyte in each aliquot and the standard deviation (s) of the recovery of the
analyte.
9.2.2.3 Compare X and s for each analyte with the corresponding limits for initial precision
and recovery in Table 2. If s and X meet the acceptance criteria, system performance
is acceptable and analysis of blanks and samples may begin. If, however, s exceeds the
precision limit or X falls outside the range for accuracy, system performance is
unacceptable. The laboratory should correct the problem and repeat the test (Section
9.2.2.1).
9.2.3 Quality control sample (QCS)—The QCS must be prepared from a source different from
that used to produce the calibration standards. River/reagent water and marine water that
contain certified concentrations of total As may be purchased. Certified reference materials
for As species are not currently available. When beginning use of this method and on a
quarterly basis, or as required to meet data quality needs, the calibration standards and
acceptable instrument performance must be verified with the preparation and analyses of a
QCS (Section 7.10). To verify the calibration standards, the determined mean concentration
from three analyses of the QCS must be within ± 10% of the stated QCS value. If the QCS
is not within the required limits, an immediate second analysis of the QCS is recommended
to confirm unacceptable performance. If the calibration standards and/or acceptable
instrument performance cannot be verified, the source of the problem must be identified and
corrected before proceeding with further analyses.
9.3 Method Accuracy—To assess the performance of the method on a given sample matrix, the laboratory
must perform matrix spike (MS) and matrix spike duplicate (MSB) sample analyses on 10% of the
samples from each site being monitored, or at least one MS sample analysis and one MSB sample
analysis must be performed for each sample set (samples collected from the same site at the same
time, to a maximum of 10 samples), whichever is more frequent.
9.3.1 The concentration of the MS and MSB is determined as follows:
9.3.1.1 If, as in compliance monitoring, the concentration of analyte(s) in the sample is being
checked against a regulatory concentration limit, the spike must contain the analyte(s)
at that limit or at one to five times the background concentration, whichever is greater.
9.3.1.2 If the concentration(s) is not being checked against a regulatory limit, the
concentration(s) must be at one to five times the background concentration or at one to
five times the ML(s) in Table 1, whichever is greater.
9.3.2 Assessing spike recovery
9.3.2.1 Betermine the background concentration (B) of As species by analyzing one sample
aliquot according to the procedures in Section 11.0.
9.3.2.2 Prepare a matrix spiking solution that will produce the appropriate level (Section 9.3.1)
of analyte(s) of interest in the sample when the spiking solution is added.
9.3.2.3 Spike two additional aliquots with the matrix spiking solution and analyze these
aliquots to determine the concentration after spiking (A).
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Method 163 2
9.3.2.4 Calculate each percent recovery of the matrix spike and matrix spike duplicate by
using Equation 1.
Equation 1
A-B
P= 100*
T
Where P = Percent recovery of the spike
A = Concentration of the spiked aliquot
B = Background concentration of the sample
T = Known value of the spike
9.3.3 Compare the percent recovery (P) with the corresponding QC acceptance criteria in Table 2.
If P falls outside the designated range for recovery, the result has failed the acceptance
criteria.
9.3.3.1 If the system performance is unacceptable, analyze the calibration verification standard
(CALVER, Section 9.5.2) for water samples, or the ongoing precision and recovery
sample (Section 9.7) for tissue samples. If the CALVER or OPR is within acceptance
criteria (Table 2), the analytical system is within specified limits and the problem can
be attributed to the sample matrix.
9.3.3.2 For samples that exhibit matrix problems, further isolate As species from the sample
matrix using chelation, extraction, concentration, or other means, and repeat the
accuracy test (Sections 9.3.2).
NOTE: The use of these techniques to reduce matrix problems may affect the speciation of the As
in solution.
9.3.3.3 If matrix problems cannot be corrected and the recovery for As species remains outside
the acceptance criteria, the analytical result in the unspiked sample is suspect and may
not be reported or used for permitting or regulatory compliance purposes.
9.3.4 Recovery for samples should be assessed and records maintained.
9.3.4.1 After the analysis of five samples of a given matrix type (river water, lake water, etc.)
for which As species pass the tests in Section 9.3.3, compute the average percent
recovery (P) (P = percent recovery in 9.3.2.4) and the standard deviation of the percent
recovery (SP). 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%.
9.3.4.2 Update the accuracy assessment in each matrix regularly (e.g., after each 5-10 new
measurements).
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Method 163 2
9.4 Precision of MS/MSB
9.4.1 Calculate the relative percent difference (RPB) between the MS and MSB using the
concentrations found in the MS and MSB (Equation 1). Bo not use the recoveries
calculated in Section 9.3.2.4 for this calculation because the RPB of recoveries is inflated
when the background concentration is near the spike concentration.
Equation 2
RPD= 1 00*
Where:
RPB = Relative percent difference
B] = Concentration of the analyte in the MS sample
B2 = Concentration of the analyte in the MSB sample
9.4.2 Compare the RPB with the limits in Table 2. If the criteria are not met, the analytical
system performance is judged to be unacceptable. Correct the problem and reanalyze all
samples in the sample set associated with the MS/MSB that failed the RPB test.
9.5 Calibration verification (also see Section 10.2)
9.5.1 Calibration verification (CALVER) shall be performed immediately after the analytical
system is calibrated or before analyzing any samples in a sample batch. In addition, the
CALVER standard shall be analyzed after every 10 samples and after the last analytical
sample in a sample batch. Refer to Section 10.2.2 and 10.2.3 for procedures on analyzing
the CALVER standard.
9.5.2 Recovery of the CALVER standard must be within the control limits specified in Table 2. If
recovery of the CALVER standard is outside the control limits in Table 2, the analysis must
be stopped, the problem corrected, the instrument recalibrated, and the calibration verified.
Samples processed after the last satisfactory calibration verification must be re-analyzed.
9.6 Blanks—Blanks are analyzed to demonstrate freedom from contamination.
9.6.1 Calibration blanks- A calibration blank consists of river/reagent water placed in the reaction
vessel and analyzed like a sample (Section 11.4 and 11.5). At least one calibration blank
must be analyzed after calibration. A calibration blank is also analyzed after each analysis
of the CALVER standard (Section 9.5). If As species or any potentially interfering
substance is found in the blank at a concentration equal to or greater than the MBL (Table
1), sample analysis must be halted, the source of the contamination determined, the problem
corrected, and the sample batch and a fresh calibration blank reanalyzed.
9.6.2 Method blanks—The method blank is an aliquot of river/reagent water or corn oil (tissue
reference matrix; Section 7.14) that is treated exactly as a sample including exposure to all
glassware, equipment and reagents that are used with samples. It is used to determine if
analytes or interferences are present in the laboratory environment, the reagents, or the
apparatus.
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Method 163 2
9.6.2.1 Prepare a minimum of 1 method blank with each sample batch (samples of the same
matrix started through the preparation process on the same 12-hour shift, to a
maximum of 20 samples). Three method blanks are preferred.
NOTE: Method blanks for water samples are identical to the calibration blanks (see Section
9.6.1). Analyze the method blank immediately after analysis of the CALVER (Section 9.5) for water
samples, or OPR (Section 9.7) for tissue samples, to demonstrate freedom from contamination.
9.6.2.2 If As species or any potentially interfering substance is found in the blank at a
concentration equal to or greater than the MDL (Table 1), sample analysis must be
halted, the source of the contamination determined, the problem corrected, and the
sample batch and a fresh method blank reanalyzed.
9.6.2.3 Alternatively, if a sufficient number of method 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.
9.6.2.4 If the result for a single method blank remains above the MDL 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 or used for permitting or regulatory compliance purposes. Stated another
way, results for all initial precision and recovery tests (Section 9.2) and all samples
must be associated with an uncontaminated method blank before these results may be
reported or used for permitting or regulatory compliance purposes.
9.6.3 Field blanks for water samples
9.6.3.1 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 10 samples). If the samples are filtered
for the determination of dissolved As and/or As species, the field blank shall be filtered
as well. Analyze the blank immediately before analyzing the samples in the batch.
9.6.3.2 If As species or any potentially interfering substance is found in the field blank at a
concentration equal to or greater than the ML (Table 1), 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 or used for permitting or
regulatory compliance purposes.
9.6.3.3 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.
9.6.3.4 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 before the next sampling
event.
9.6.4 Equipment blanks—Before any sampling equipment is used at a given site, the laboratory or
cleaning facility is required to generate equipment blanks to demonstrate that the sampling
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Method 163 2
equipment is free from contamination. Two types of equipment blanks are required: bottle
blanks and sampler check blanks.
9.6.4.1 Bottle blanks—After undergoing appropriate cleaning procedures (Section 6.1.2),
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
river/reagent water (Section 7.1) 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.
9.6.4.2 Sampler check blanks for water samples—Sampler check blanks are generated in the
laboratory or at the equipment cleaning contractor's facility by processing river/reagent
water (Section 7.1) through the sampling devices using the same procedures that are
used in the field (see Sampling Method). Therefore, the "clean hands/dirty hands"
technique used during field sampling should be followed when preparing sampler check
blanks at the laboratory or cleaning facility.
9.6.4.2.1 Sampler check blanks are generated by filling a large carboy or other
container with river/reagent water (Section 7.1) and processing the
river/reagent water (Section 7.1) through the equipment using the same
procedures that are used in the field (see Sampling Method). 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. "Clean hands/dirty hands"
techniques must be used.
9.6.4.2.2 The sampler check blank must be analyzed using the procedures in this
method. If As and/or As species 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 must be demonstrated to
be free from As and/or As species before the equipment may be used in the
field.
9.6.4.2.3 Sampler check blanks must 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 - Because water samples do not require digestion prior to analysis,
OPR samples are only required for tissue samples. CALVER analysis in Section 9.5 is equivalent to
the analysis of an aqueous OPR.
9.7.1 For each sample batch (i.e., samples of the same matrix started through the extraction
process on the same 12-hour shift, to a maximum of 20 samples), prepare an ongoing
precision and recovery (OPR) aliquot in the same manner as IPR aliquots (Section 9.2.2).
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Method 163 2
9.7.2 Analyze the OPR aliquot before analyzing the method blank and samples from the same
batch.
9.7.3 Compute the percent recovery of As species in the OPR aliquot.
9.7.4 Compare the recovery in the OPR sample to the limits for ongoing recovery in Table 2. If
the acceptance criteria are met, system performance is acceptable and analysis of blanks and
samples may proceed. If, however, recovery falls outside of the range given, the analytical
processes are not being performed properly. Correct the problem, prepare the sample batch
again, and repeat the OPR test.
9.7.5 Add results that pass the specifications to IPR and previous OPR data for As species.
Update QC charts to form a graphic representation of continued laboratory performance.
Develop a statement of laboratory accuracy 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%.
9.8 The specifications in this method can be met if the instrument used is calibrated properly and then
maintained in a calibrated state. A given instrument will provide the most reproducible results if
dedicated to the settings and conditions required for the analyses of As and/or As species by this
method.
9.9 Depending on specific program requirements, field duplicates may be collected to determine the
precision of the sampling technique. The relative percent difference (RPD, Equation 2) between field
duplicates should be less than 20%.
10.0 Calibration and Standardization
10.1 Calibration—Calibration is required before any samples or method blanks are analyzed.
10.1.1 Standards are analyzed by addition of measured aliquots of the working standard solution A
(Section 7.13.5) directly into the reaction vessel that has been pre-filled with river/reagent
water (70 mL for the 125-mL reaction vessel; 5 mL for the 30-mL reaction vessel). Proceed
with analysis of the standards following procedures in Section 11.4.
10.1.2 The calibration must contain 3 or more non-zero points. For a given As species, the lowest
calibration point must be less than or equal to the ML shown in Table 1.
10.1.3 Calculate the calibration factor (CF) for IA, MMA and DMA in each calibration standard
using the following equation.
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Method 163 2
Equation 3
CF =
Where,
CF = Calibration factor [peak area or height units / ng]
Rx = Peak height or area for As species in standard [peak area or height units]
mx = Mass of As species in standard analyzed
10.1.4 For each analyte of interest, calculate the mean calibration factor (CFm), the standard
deviation of the CFm (SD), and the relative standard deviation (RSD) of the mean, where
RSD = 100 x SD/CFm.
10.1.5 Appropriateness of CF—If the RSD as calculated in Section 10.1.4 is less than 20%, the
CFm may be used to calculate sample concentrations. Otherwise, use weighted linear
regression to calculate a slope and intercept for the calibration line.
10.1.6 When analyzing for As3+, the calibration line for IA can be used.
10.1.7 Following calibration, analyze a calibration blank. The concentrations of As and As species
in the calibration blank be less than the MDL.
10.2 Calibration verification—A calibration verification is performed immediately after calibration
and after analysis of a maximum of every 10 samples thereafter (Section 10.2.2). Blanks and
samples may not be analyzed until these criteria are met.
10.2.1 Verify the specificity of the instrument for As and adjust the wavelength or tuning until the
resolving power (Table 3) specified in this method is met.
10.2.2 Calibration verification for IA, MMA and DMA
10.2.2.1 Calibration verification (CALVER)—Prepare the CALVER standard by adding a
measured volume of working standard solution B to the reaction vessel (pre-filled
with river/reagent water) corresponding to the mid-level standard used to establish
the calibration line. The CALVER standard is then purged and analyzed for IA,
MMA and DMA following procedures in Section 11.4. Compute the percent
recovery of As species using the initial calibration.
10.2.2.2 Compare the recovery with the corresponding limit for calibration verification in
Table 2. If acceptance criteria are met, system performance is acceptable and
analysis of blanks and samples may continue using the response from the initial
calibration. If acceptance criteria are not met, system performance is
unacceptable. Locate and correct the problem and/or prepare a new calibration
verification standard and repeat the test (Sections 10.2.1 through 10.2.3), or
recalibrate the system (Sections 10.1 and 10.2). All samples after the last
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Method 163 2
acceptable calibration verification must be reanalyzed.
10.2.3 Calibration verification for As3+
10.2.3.1 Before the As3+ analysis of samples, the CALVER standard is analyzed at the
beginning of an analytical batch, following every 10 samples, and at the end of an
analytical batch. The CALVER standard is prepared by adding a measured
volume of working standard solution B to the reaction vessel pre-filled with
river/reagent water (70 or 5 mLs). The CALVER standard should correspond to
the mid-level standard used to establish the calibration line. The CALVER
standard is then purged and analyzed for As3+ in Section 11.5. Compute the
percent recovery of As3+ using the initial calibration.
10.2.3.2 Compare the recovery with the corresponding limit for calibration verification in
Table 2. If acceptance criteria are met, system performance is acceptable and
analysis of blanks and samples may continue using the response from the initial
calibration. If acceptance criteria are not met, system performance is
unacceptable. Locate and correct the problem and/or prepare a new calibration
check standard and repeat the test (Sections 10.2.1 through 10.2.3), or recalibrate
the system (Sections 10.1 and 10.2). If the recovery does not meet the acceptance
criteria specified in Table 2, analyses must be halted and the problem corrected.
All samples after the last acceptable calibration verification for As3+ must be
reanalyzed for As3+.
10.3 Analyze a calibration blank following every calibration verification to demonstrate that there is
no carryover of the analytes of interest and that the analytical system is free from contamination.
The concentrations of As and As species in the calibration blank must be less than the MDL. If
the concentration of an analyte in the blank result is equal to or exceeds the MDL, correct the
problem, verify the calibration (Section 10.1), and repeat the analysis of the calibration blank.
11.0 Sample Preparation and Analysis
11.1 Set up the AAS system according to manufacturer's instructions. The settings in Tables 3 and 4
can be used as a guide. Calibrate the instrument according to Section 10.1.
NOTE: Precision and sensitivity are affected by gas flow rates and these must be individually optimized
for each system using the settings in Table 5 as an initial guide.
11.2 To light the flame, turn on the air and H2, and expose the end of the quartz cuvette to a flame. At
this point, a flame will be burning out the ends of the tube. Allow the tube to heat for
approximately five minutes, then place a flat metal spatula over each end of the tube in sequence.
An invisible air/hydrogen flame should now be burning in the center of the cuvette. To check for
the flame, place a mirror near the end of the tube and observe condensation of water vapor or
turn-off the room light to observe the flame.
11.3 Tissue samples large enough to sub-sample must be homogenized to a fine paste with a stainless
steel mill, or finely chopped with stainless steel tools on an acid-cleaned, plastic cutting board.
Clean sample handling techniques must be followed. Digest tissue samples by adding 10 mL of
2M HC1 to 0.5 g of either wet or dry tissue in a 25-mL glass scintillation vial. Cap the vial with
a fluoropolymer-lined lid and heat overnight (16 hours) in an oven at 75 - 85 °C. Cool and
Draft, January 2001 21
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Method 163 2
analyze the overlying liquid. Tissue may also be digested in 2M NaOH overnight at 75 - 85 °C;
however, As+3 and As+5 are more stable in HC1 than NaOH. If only IA, MMA, and DMA are
required, the advantage of the NaOH digestion is that, if it is available, ICP-MS can be used to
quantify total As (Reference 16.14) in the digestate.
11.4 Inorganic As, MMA, and DMA determination.
11.4.1 Purging of Samples
11.4.1.1 To achieve a detection limit < 0.01 (jg/L, place a known volume of aqueous
sample (up to 70 mL) into the large (125-mL) reaction vessel. If less than 70 mL
of sample is used, add sufficient river/reagent water (Section 7.1) to result in a
total volume of 70 mL. Add 5.0 mL of 6MHC1. Set the four-way valve on the
reaction vessel to pass the flow of He through the sample and onto the trap and
begin purging the vessel with He.
11.4.1.2 To analyze tissue digestates or to analyze water samples with a detection limit >
0.01 Aig/L, place a known volume of aqueous sample (up to 5 mL) or tissue
digestate (up to 2 mL) into the small (30 mL) reaction vessel. Add 1.0 mL of 6M
HC1. Set the four-way valve on the reaction vessel to pass the flow of He through
the sample and onto the trap and begin purging the vessel with He.
11.4.1.3 Lower the trap into a Dewar flask containing LN2 and top the flask off with LN2
to a constant level.
11.4.1.4 For a large reaction vessel, add 10 mL of NaBH4 solution slowly (over a period of
approximately two minutes) through the rubber septum with a disposable
hypodermic syringe and begin timing the reaction. For the small reaction vessel,
add 2.0 mL of NaBH4 slowly over a 1-minute period. After seven minutes, turn
the stopcock on the four-way valve to bypass the reaction vessel and pass helium
directly to the trap. Arsines are purged from the sample onto the cooled glass trap
packed with 15% OV-3 on Chromosorb® W AW DMCS, or equivalent.
11.4.2 Trap desorption and AAS analysis
11.4.2.1 Quickly remove the trap from the LN2, activate the heating coils to heat the trap,
and begin recording output from the AAS system. The transfer line is maintained
at 75 - 85 °C. The trapped arsines are thermally desorbed, in order of increasing
boiling points, into an inert gas stream that carries them into the quartz furnace of
an atomic absorption spectrophotometer for detection. The first arsine to be
desorbed is AsH3, which represents total inorganic As in the sample. The MMA
and DMA are desorbed and detected several minutes after the arsine.
11.4.2.2 To ensure that all organic reduction products have been desorbed from the trap,
maintain the trap temperature at 65 - 85 °C and keep He flowing through the trap
for at least three minutes between samples.
11.4.3 The trap should be cooled for one minute before re-using for another analysis to reduce the
possibility of cracking.
22 Draft, January 2001
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Method 163 2
11.5 Arsenite (As+3) Determination
11.5.1 pH Adjustment
11.5.1.1 To analyze water samples with a detection limit < 0.01 Aig/L, place a known
volume (up to 70 mL) in the large (125-mL) reaction vessel. If less than 70 mL of
sample is used, add sufficient river/reagent water (Section 7.1) to result in a total
volume of 70 mL. Add 3.0 mL of Tris buffer to bring the sample's pH to 5 to 7.
If the sample is strongly acidic or basic, it must be either neutralized or have more
buffer added to obtain a pH of 5 to 7.
11.5.1.2 To analyze tissue digestates or to analyze water samples with a detection limit >
0.01 Aig/L, place a known volume of aqueous sample (up to 5 mL) or tissue
digestate (up to 2 mL) in the small reaction vessel. Add 1.0 mL of Tris buffer. If
the sample is strongly acidic or basic, it must be either neutralized or have more
buffer added to obtain a pH of 5 to 7.
11.5.2 Purging of samples—For a large reaction vessel, add 3.0 mL of NaBH4 solution quickly
(about 10 seconds) through the rubber septum with a disposable hypodermic syringe and
begin timing the reaction. For a small reaction vessel, add 1.0 mL of NaBH4 in a short
injection (about 10 seconds). The injections are quicker for As+3 determinations than for
Inorganic As, MMA, DMA determinations (Section 11.4.1.4) because rapid evolution of H2
does not occur at a neutral pH. After seven minutes, turn the stopcock on the four-way
valve to bypass the reaction vessel and pass helium directly to the trap. Arsines are purged
from the sample onto the cooled glass trap packed with 15% OV-3 on Chromosorb® W AW
DMCS, or equivalent.
11.5.3 Trap desorption and AAS analysis—Desorption of arsines from the trap follows the same
procedure as in Sections 11.4.2 through 11.4.3 to complete the determination of As+3
concentration. During this procedure, small, irreproducible quantities of organic arsines
may be released at this pH and should be ignored. This separation of arsenite is
reproducible and essentially 100% complete.
11.6 Arsenate (As+5) determination—The concentration of As+5 is calculated by subtracting the As+3
determined in Section 11.5 from the total inorganic As determined on an aliquot of the same
sample in Section 11.4.
12.0 Data analysis and calculations
12.1 For water samples, compute the concentration of As species in ng/L using the calibration data
(Section 10.1):
Draft, January 2001 23
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Method 163 2
C
Equation 4
Rx
L
CFV
Where:
Rx = Peak height or area for As species in the sample [peak height or area units]
CFm = Mean calibration factor for As species [peak height or area units l\\g\
Vs = Volume of sample purged and analyzed [L]
For tissue samples, compute the concentration of As species in (jg/g as follows:
Equation 5
c —
g
Where:
Rx = Peak height or area As species in the digestate [peak height or area units]
CFm = Mean calibration factor for As species [peak height or area units l\\g\
V^est = Total volume of tissue digestate [mL]
Vd = Volume of digestate added to reaction vessel [mL]
n\ = mass of sample digested [g]
12.2 If the concentration exceeds the calibration range, dilute the sample by successive factors of 10
until the concentration is within the calibration range.
12.3 Reporting
12.3.1 Report results for each As species at or above the ML, in (jg/L or (jg/g, to three significant
figures. Report results for each As species in samples below the ML as less than the value
of the ML, or as required by the regulatory authority or in the permit. Report results for
each As species in field blanks at or above the ML, in (jg/L or (jg/g, to three significant
figures. Report results for each As species in field blanks below the ML but at or above the
MDL to two significant figures. Report results for each As species not detected in field
blanks as less than the value of the MDL, or as required by the regulatory authority or in the
permit.
12.3.2 Report results for each As species in samples, method blanks, and field blanks separately,
unless otherwise requested or required by a regulatory authority or in a permit. If blank
correction is requested or required, subtract the concentration of each As species in the
method blank, average of multiple method blanks, or field blank from the concentration of
24 Draft, January 2001
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Method 163 2
the respective As species in the sample to obtain the net sample As species concentration.
Among the preceding blanks, only one may be subtracted.
12.3.3 Results from tests performed with an analytical system that is not in control must not be
reported or otherwise used for permitting or regulatory compliance purposes, but does not
relieve a discharger or permittee of reporting timely results.
13.0 Method Performance
Tables 1 contains MDLs and MLs for As species in water and tissue matrices. The QC acceptance criteria
in Table 2 are based on quality control data generated during As speciation analysis by Method 1632 for
the Cook Inlet Study (1998). Details on how the criteria were developed can be found in Reference 16.16.
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. Many opportunities for pollution prevention exist in
laboratory operation. 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. When wastes cannot be feasibly reduced at the source, the Agency recommends
recycling as the next best option. The acids used in this method should be reused as practicable
by purifying with electrochemical techniques. The only other chemicals used in this method are
the neat materials used in preparing standards. These standards are used in extremely small
amounts and pose little threat to the environment when managed properly. Standards should be
prepared in volumes consistent with laboratory use to minimize the disposal of excess volumes of
expired standards.
14.2 For information about pollution prevention that may be applied to laboratories and research
institutions, consult Less is Better: Laboratory Chemical Management for Waste Reduction,
available from the American Chemical Society's Government Affairs Publications ,1155 16th
Street NW, Washington DC 20036, 202/872-4600, orgovtrelations@acs.org.
15.0 Waste Management
15.1 The laboratory is responsible for complying with all federal, state, and local regulations
governing waste management, particularly hazardous waste identification rules and land disposal
restrictions, and for protecting the air, water, and land by minimizing and controlling all releases
from fume hoods and bench operations. Compliance with all sewage discharge permits and
regulations is also required.
15.2 Acids and samples at pH < 2 must be either neutralized before being disposed or handled as
hazardous waste.
15.3 For further information on waste management, consult The Waste Management Manual for
Laboratory Personnel and Less is Better: Laboratory Chemical Management for Waste
Reduction, both available from the American Chemical Society's Government Affairs
Publications, 1155 16th Street NW, Washington, DC 20036.
Draft, January 2001 25
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Method 163 2
16.0 References
16.1 Crecelius, E.A., Bloom, N.S., Cowan, C.E., and Jenne, E.A., Speciation of Selenium and
Arsenic in Natural Waters and Sediments, Volume 2: Arsenic Speciation. Final Report,
Prepared for Electric Power Research Institute, Palo Alto, CA by Battelle, Pacific Northwest
Laboratories, Richland, WA, 1986.
16.2 Andreae, M.O. "Determination of Arsenic Species in Natural Waters," Anal. Chem. 1977, 49,
820.
16.3 Method 1669, "Method for Sampling Ambient Water of Metals at EPA Ambient Criteria
Levels," U.S. Environmental Protection Agency, Office of Water, Office of Science and
Technology, Engineering and Analysis Division (4303), 401 M St SW, Washington, DC 20460
(January 1996).
16.4 Patterson, C.C. and Settle, D.M. "Accuracy in Trace Analysis"; In National Bureau of
Standards Special Publication 422; LaFleur, P.O., Ed., U.S. Government Printing Office,
Washington, DC, 1976.
16.5 "Working with Carcinogens," Department of Health, Education, and Welfare, Public Health
Service, Centers for Disease Control, NIOSH, Publication 77-206, August 1977, NTIS PB-
277256.
16.6 "OSHA Safety and Health Standards, General Industry," OSHA 2206, 29 CFR 1910.
16.7 "Safety in Academic Chemistry Laboratories," ACS Committee on Chemical Safety, 1979.
16.8 "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.
16.9 Andrae, M.O., 1983. "Biotransformation of arsenic in the marine environment." InW.H.
Lederer and R.J. Fensterheim (Eds.), Arsenic: Industrial, Biomedical, Environmental
Perspectives. Van Nostrand-Reinhold, New York, pp. 378-392.
16.10 Lauenstein, G.G. and A.Y. Cantillo (Eds.). July, 1983. Silver Spring, MD. NOAA Technical
Memorandum NOS ORCA 71. Sampling and Analytical Methods of the National Status and
Trends Program National Benthic Surveillance and Mussel Watch Projects 1984-1992, Volume
1: Overview and Summary of Methods.
16.11 Aggett, J. and Kriegman, M.R. "Preservation of Arsenic(III) and Arsenic(V) in Samples of
Sediment Interstitial Water," Analyst 1987, 112, 153.
16.12 Wing, R., D. K. Nordstrom, and G.A. Parks. "Treatment of Groundwater Samples to Prevent
Loss or Oxidation of Inorganic Arsenic Species."; In Analytical Characterization of Arsenic in
Natural Waters. R. Wing's Master's Thesis, 1987, Stanford University.
26 Draft, January 2001
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Method 163 2
16.13 Crecelius, E. and J. Yager. "Intercomparison of Analytical Methods for Arsenic Speciation in
Human Urine." Environmental Health Perspectives 1997,105, 650.
16.14 Method 1640, "Determination of Trace Elements in Water by Preconcentration and Inductively
Coupled Plasma-Mass Spectrometry," U.S. Environmental Protection Agency, Office of Water,
Office of Science and Technology, Engineering and Analysis Division (4303), 401 M St SW,
Washington, DC 20460 (April, 1997). Draft.
16.15 "Results of the EPA Method 1632 Validation Study," July 1996. Available from the EPA
Sample Control Center, 6101 Stevenson Avenue, Alexandria, VA 22304, 703-461-2100.
16.16 "Development of Quality Control Criteria for Method 1632, Revision A," July 2000. Available
from the EPA Sample Control Center, 6101 Stevenson Avenue, Alexandria, VA 22304, 703-
461-2100.
17.0 Glossary
The definitions and purposes below are specific to this method, but have been conformed to common usage
as much as possible.
17.1 Ambient water—Water in the natural environment (e.g., river, lake, stream, and other receiving
water), as opposed to an effluent discharge.
17.2 Equipment blank—An aliquot of river/reagent water (Section 7.1) that is subjected in the
laboratory to all aspects of sample collection and analysis, including contact with all sampling
devices and apparatus. The purpose of the equipment blank is to determine if the sampling
devices and apparatus for sample collection have been adequately cleaned before shipment to the
field site. An acceptable equipment blank must be achieved before the sampling devices and
apparatus are used for sample collection. In addition, equipment blanks should be run on
random, representative sets of gloves, storage bags, and plastic wrap for each lot to determine if
these materials are free from contamination before use.
17.3 Field blank—An aliquot of river/reagent water (Section 7.1) that is placed in a sample container
in the laboratory, shipped to the field, and treated as a sample in all respects, including contact
with the sampling devices and exposure to sampling site conditions, storage, preservation, and all
analytical procedures, which may include filtration. The purpose of the field blank is to
determine if the field or sample transporting procedures and environments have contaminated the
sample.
17.4 Field duplicates (FD1 and FD2)—Two separate samples collected in separate sample bottles at
the same time and place under identical circumstances and treated exactly the same throughout
field and laboratory procedures. Analyses of FD1 and FD2 give a measure of the precision
associated with sample collection, preservation, and storage, as well as with laboratory
procedures.
17.5 Initial precision and recovery (IPR)—Four aliquots of the ongoing precision and recovery
standard analyzed to establish the ability to generate acceptable precision and accuracy. IPR
tests are performed before a method is used for the first time and any time the method or
instrumentation is modified.
Draft, January 2001 27
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Method 163 2
17.6 Matrix spike (MS) and matrix spike duplicate (MSB)—Aliquots of an environmental sample to
which known quantities of the analytes are added in the laboratory. The MS and MSB are
analyzed exactly like samples. Their purpose is to quantify the bias and precision caused by the
sample matrix. 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 MSB corrected for
background concentrations.
17.7 May—This action, activity, or procedural step is optional.
17.8 May not—This action, activity, or procedural step is prohibited.
17.9 Method blank—An aliquot of river/reagent water (Section 7.1) or corn oil (Section 7.14) that is
treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents,
internal standards, and surrogates that are used with samples. The method blank is used to
determine if analytes or interferences are present in the laboratory environment, the reagents, or
the apparatus.
17.10 Minimum level (ML)—The lowest level at which the entire analytical system must give 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-specified sample
weights, volumes, and cleanup procedures have been employed. The ML is calculated by
multiplying the MBL by 3.18 and rounding the result to the number nearest to (1, 2, or 5) x 1 On,
where n is an integer.
17.11 Must—This action, activity, or procedural step is required.
17.12 Ongoing precision and recovery (OPR)—A method blank spiked with known quantities of
analytes. The OPR is analyzed exactly like a sample. Its purpose is to assure that the results
produced by the laboratory remain within the limits specified in the referenced methods for
precision and accuracy.
17.13 Quality control sample (QCS)—A sample containing all or a subset of the analytes at known
concentrations. The QCS is obtained from a source external to the laboratory or is prepared
from a source of standards different from the source of calibration standards. It is used to check
laboratory performance with test materials prepared external to the normal preparation process.
17.14 Reagent water—Water demonstrated to be free of As, As species, and potentially interfering
substances at the MBLs for As and/or As species.
17.15 River Water—Freshwater containing arsenic species at concentrations below the MBLs.
17.16 Should—This action, activity, or procedural step is suggested but not required.
17.17 Stock solution—A solution containing an analyte that is prepared using a reference material
traceable to EPA, the National Institute of Science and Technology (NIST), or a source that will
attest to the purity and authenticity of the reference material.
28 Draft, January 2001
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Method 163 2
18.0 Tables and Figures
TABLE 1. ARSENIC SPECIATION ANALYSIS USING METHOD 1632: METHOD
DETECTION LIMIT (MDL) AND MINIMUM LEVEL (ML)1
Water2
Analyte
Inorganic Arsenic (As+3 +As+5)
Arsenite (As+3)
Monomethylarsonic acid (MMA)
Dimethylarsinic acid (DMA)
MDL
0.003 Aig/L
0.003 Aig/L
0.004 Aig/L
0.02 Aig/L
ML
0.01 A^g/L
0.01 A^g/L
0.01 Aig/L
0.05 Aig/L
Tissue3
MDL
0.03 Aig/g
0.02 A/g/g
0.01 A^g/g
0.04 A^g/g
ML
0.10A,g/g
0.10^8/g
0.05 A^g/g
0.10A,g/g
1 MDL determined by the procedure in 40 CFR Part 136, Appendix B.
2 MDL for inorganic As in water was obtained from a validation study involving two
laboratories (Ref. 16.15). MDL for As+3, MMA and DMA in water was obtained from data
provided by Frontier Geosciences (Ref. 16.16).
3 MDL for tissue was determined from spiked corn oil samples by Battelle Marine Sciences
Laboratory (Ref. 16.16).
TABLE 2. QUALITY CONTROL ACCEPTANCE CRITERIA FOR EPA METHOD 16321
IPR (Section 9.2)
Analyte2
IA
As+3
MMA
DMA
s
< 25%
< 25%
< 20%
< 30%
X
60-140%
40-160%
70-130%
50-150%
OPR
(Section 9.7)
50-150%
30-170%
60-140%
40-160%
Calibration
Verification
(Section 9.5)
80-120%
70-130%
80-120%
70-130%
MS/MSD
(Section 9.3)
%R
50-150%
30-170%
60-140%
40-160%
RPD
< 35%
< 35%
< 25%
< 40%
1 Acceptance criteria based on quality control data generated during As speciation analysis for the Cook
Inlet Study (1998). Details can be found in Reference 16.16.
2 IA - Inorganic arsenic (As+3 + As+5); MMA - monomethylarsonic acid; DMA - dimethylarsinic acid.
Draft, January 2001
29
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Method 163 2
TABLE 3: TYPICAL SPECTROPHOTOMETER SETTINGS
Parameter Typical Setting
EDL energy 59
EDL power 8 W
Wavelength 193.7 nm
Slit width O.Vnm
TABLE 4: TYPICAL FLOW RATES AND PRESSURES FOR GASES IN THE HYDRIDE
GENERATION SYSTEM
Gas Flow Rate (mL/min) Pressure (Ib/in2)
He 150 10
H2 350 20
Air 180 20
30 Draft, January 2001
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Method 163 2
Figure 1. Arsenic Speciation Apparatus: (a) Quartz Cuvette Burner Tube, (b) Reaction Vessel, and
(c) Schematic Diagram
1B
REACTION VESSEL
H, Input
From Trap
1C
SCHEMATIC DIAGRAM
ToBumw
80-C
W»« -wound
Pyrfl« U-Tub*
ChromBMXb "W
Arwnic
I E.D.L.
1 T
Chart fUcorOvr Output
Drq/f, January 2001
31
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