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/
Draft, January 2001

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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.

Draft, January 2001                                                                              1

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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.
                                                                                 Draft, January 2001

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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.
Draft, January 2001

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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.
10                                                                                Draft, January 2001

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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).
14                                                                               Draft, January 2001

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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.
Draft, January 2001                                                                                19

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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

20                                                                                Draft, January 2001

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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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