gffi fU-
&EPA   Method 1632: Determination of
        Inorganic Arsenic in Water by
        Hydride Generation Flame Atomic
        Absorption
                                    ' Printed on Recycled Paper

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 Method 1632
                                    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  (BAD).  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 method has been reviewed and approved for publication by 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.


Questions  concerning this method or its application should be addressed to:

W.A. Telliard
USEPA Office of Water
Analytical Methods Staff
Mail Code 4303
401 M Street, SW
Washington, DC 20460
Phone:  202/260-7120
Fax:   202/260-7185
                                                                             Draft, April 1995

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                                                                                      Method 1632
                                          Introduction

This analytical method was designed to support water quality monitoring programs authorized under the
Clean Water Act.  Section 304(a) of the Clean Water Act requires EPA to publish water quality criteria
that reflect the latest scientific knowledge about  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.

Section 303 of the Clean Water Act requires states 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 waterbody
or a segment of a waterbody, the water quality criteria that are necessary to protect the designated use or
uses,  and an antidegradation policy.  These water quality standards serve two purposes:  (1) they establish
the water quality goals for a specific waterbody, and (2) they are the basis for establishing water quality-
based treatment controls and strategies beyond the technology-based controls required by Sections 301(b)
and 306 of the Clean Water Act.

In  defining water quality standards, the  state may  use narrative criteria,  numeric criteria,  or  both.
However, the 1987 amendments to the Clean Water Act 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 are as  much as 280 times lower than those achievable using
existing EPA methods and required to support technology-based permits. Therefore, EPA developed new
sampling and analysis methods to specifically  address state needs for measuring toxic metals at water
quality criteria 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 (57
FR 60848).  This rule includes water quality criteria 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 flame atomic
absorption techniques.

In developing these methods, EPA  found that one of the greatest difficulties in measuring pollutants at
these  levels 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 analytical
method,  therefore, is designed to provide the level of protection necessary to preclude contamination in
nearly all situations.   It is also designed to provide the procedures necessary to produce reliable results
at the lowest  possible water quality criteria published by EPA.  In recognition of the variety of situations
to which this method may be applied, and in recognition of continuing technological advances, the method
is performance based. Alternative procedures may be used, so long as those procedures are demonstrated
to yield reliable results.

Requests for  additional copies should be directed  to:

U.S. EPA NCEPI
11029 Kenwood Road
Cincinnati, OH 45242
513/489-8190

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 Method 1632
     Note:  This method is intended to be performance based, and the laboratory is permitted to omit
     any step or modify any procedure if all performance requirements set forth in this method are
     met. The laboratory is not allowed to omit any quality control analyses. The terms "must,"
     "may," and "should" are included throughout this method and are intended to illustrate the
     importance of the procedures in producing verifiable data at water quality criteria levels. The
     term "must" is used to indicate that researchers in trace metals analysis have found certain
     procedures essential in successfully analyzing samples and avoiding contamination; however,
     these procedures can be modified or omitted  if the laboratory can demonstrate that data quality
     is not affected.
IV
                                                                                  Draft, April 1995

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                                                                                Method 1632
                                Method  1632
                       Inorganic Arsenic  in Water by
                      Hydride Generation  Flame AA
 1.0    Scope and Application

 1.1     This method is for determination of total inorganic arsenic (As) in filtered and unfiltered water
        by hydride generation and flame 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 determination of arsenic in aqueous samples (Reference 16.2).

 1.2     This method is accompanied by Method 1669: Sampling Ambient Water for Determination of
        Trace Metals at EPA Water Quality Criteria Levels (Sampling Method).  The Sampling
        Method is necessary to ensure that contamination will not compromise trace metals
        determinations during the sampling process.

 1.3     This method is designed for measurement of dissolved and total arsenic in the range of 10-200
        ng/L. This method is not intended for determination of arsenic at concentrations normally
        found in treated and untreated discharges from industrial facilities. Existing regulations (40
        CFR Parts 400-500) typically limit concentrations in industrial discharges to the part-per-
        billion (ppb) range, whereas ambient  arsenic  concentrations are normally in the  low part-per-
        trillion (ppt)  range.

 1.4     The detection limits and quantitation  levels in this method are usually dependent on the level
        of background elements rather than instrumental limitations. The method detection limit
        (MDL; 40 CFR  136, Appendix B)  for total inorganic arsenic has been determined to be 2 ng/L
        when no background elements or interferences are present. The minimum level  (ML) has been
        established at 10 ng/L.

 1.5     The ease of contaminating water samples with the metal(s) of interest 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 gives these
       suggestions.  Additional suggestions for improvement of existing facilities may  be found in
       EPA's Guidance for 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.
Draft, April 1995

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 Method 1632
 1.6    Clean and ultraclean—The terms "clean" and "ultraclean" 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 ultraclean
        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 analyst 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.

 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 analyst who uses this method must demonstrate the ability to  generate acceptable results
        using the procedure in 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.  Before this method is used, data users should  state data quality
        objectives (DQOs) required for a project.


 2.0    Summary of Method

 2.1     A 100-2000 mL sample is collected directly into a specially cleaned, pretested, fluoropolymer,
        conventional or linear polyethylene, polycarbonate, or polypropylene bottle using sample
        handling techniques  specially designed for collection of metals at trace levels (Reference  16.3).

 2.2     The sample  is either field  or laboratory preserved by the addition of 5 mL of pretested  10%
        HNO3 per liter of sample, depending on the time between sample collection and arrival at the
        laboratory.

2.3     An aliquot of sample is removed and placed in a specially designed reaction vessel.

2.4     Before analysis, 6 M HC1  and 4% NaBH4 solution are added to convert  organic and inorganic
        arsenic to volatile arsines.

2.5     The arsines are purged from the sample onto a cooled glass  trap packed with 15% OV-3 on
        Chromasorb® WAW-DMCSO. or equivalent.
                                                                                Draft, April 1995

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                                                                                      Method 1632
 2.6     The trapped arsines are thermally desorbed, in order of increasing boiling points, into an inert
         gas stream that carries them into the flame of an atomic absorption spectrophotometer for
         detection.  The first arsine to be desorbed will be AsH3, which represents total inorganic
         arsenic in the sample.

 2.7     Quality is ensured through calibration and testing of the hydride generation, purging, and
         detection systems.
 3.0    Definitions

 3.1     As defined by this method, total inorganic arsenic means all NaBH4-reducible inorganic arsenic
         compounds found in aqueous solution. This method can be extended to measure organic
         arsenic as well.  Organic arsenic includes, but is not limited to, monomethylarsonate and
         dimethylarsonate.  In this context, "total" arsenic refers to the forms and species of arsenic, not
         to the total recoverable or dissolved fraction normally determined in an unfiltered or filtered
         sample, respectively.  In  this method,  the total recoverable fraction  will be referred to as "total
         recoverable" or "unfiltered."

 3.2     As defined by this method, dissolved inorganic arsenic means all NaBH4-reducible inorganic
         arsenic compounds found in aqueous solution filtrate after passing the sample through a 0.45-
         uM capsule filter.

 3.3    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 process constitutes one of the greatest difficulties encountered in trace metals
        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 trace metals.

 4.2     Samples may become contaminated by numerous routes. Potential sources of trace metals
        contamination  during sampling include:  metallic or metal-containing labware (e.g., talc gloves
        that contain high levels of zinc), 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 metals  contamination.
Draft, April 1995

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Method 1632
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 metal free and free from any material that may
               contain metals.

               4.3.1.1 The integrity of the results produced cannot 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 metals 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 of this method give
                      requirements and suggestions for personnel safety.

       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 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—The 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 being
               used, the apparatus should be covered with clean plastic wrap, stored in the clean
               bench or in a plastic box or 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.
                                                                                Draft, April 1995

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                                                                                      Method 1632
        4.3.6   Wear gloves—Sampling personnel must wear clean, nontalc 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 metals at ambient
               water quality criteria levels must be nonmetallic, free of material that may contain
               metals, or both.

               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  arsenic.  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 in this method and must be known
                      to be clean and metal free before proceeding.

               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, and
                      logbooks should be 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 vs.
                      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  any sampling activity resumes.

        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 metals is processed immediately after a
Draft, April 1995

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 Method 1632
                       sample containing relatively high concentrations of these metals. 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 is followed by analysis of a laboratory blank to check for
                       carryover.  Samples known or suspected to contain the lowest concentration of
                       metals 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 inorganic substances 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 metals
                       samples.

                4.3.8.3 Contamination by indirect contact—Apparatus that may 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 ambient water samples be cleaned
                       as specified in Section 11.

               4.3.8.4 Contamination by airborne paniculate 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
4.4.1    If the transfer line between the cold trap and the atomizer is not well heated, water vapor may
        condense in the line. Such condensation can interfere with the determination of
        dimethylarsine.

4.4.2    High concentrations of cobalt, copper, iron, mercury, or nickel can cause interferences through
        precipitation as reduced metals and blockage of transfer lines and fittings
                                                                                  Draft, April 1995

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                                                                                       Method 1632
 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 in this method. If primary
         solutions are prepared, 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. The references and
         bibliography at the end  of Reference  16.8 are particularly comprehensive in dealing with the
         general  subject of laboratory safety.

 5.3      Samples suspected to contain high concentrations of As 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.

        5.3.1    Facility—When samples known or suspected of containing high concentrations of
                arsenic 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 leaktight  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. 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.
Draft, April 1995

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 Method 1632
        5.3.4   Personal hygiene—Hands and forearms should be washed thoroughly after each
               manipulation and before breaks (coffee, lunch, and shift).

        5.3.5   Confinement—Isolated work  areas posted with signs, segregated glassware and tools,
               and plastic absorbent paper on bench tops will aid in confining contamination.

        5.3.6   Effluent vapors—The effluent from the AAS should pass through either a column of
               activated charcoal or a trap designed to remove As.

        5.3.7   Waste handling—Good technique includes 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 washer without contact. The washer should be run through
               a cycle before being used again for other clothing.

        5.3.10  Wipe tests—A useful method  of determining cleanliness of work surfaces and tools is
               to wipe the surface with a piece of filter paper. Extraction and analysis by this method
               can achieve a limit of detection  of less than 1 ng per wipe. Less than 0.1 pg per wipe
               indicates acceptable cleanliness; anything higher warrants further cleaning. More than
               10 pg on a wipe constitutes an acute hazard and requires prompt cleaning before
               further use of the  equipment or work space, and indicates that unacceptable work
               practices have been employed.
6.0   Apparatus and Materials

       Note: Brand names, suppliers, and part numbers are for illustration purposes only
       and no endorsement is implied. Equivalent performance may be achieved using
       apparatus and materials other than those specified here.  The laboratory is responsible
       for meeting the performance requirements of this method.
                                                                                Draft, April 1995

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                                                                                     Method 1632
6.1     Sampling equipment

        6.1.1   Sample collection bottles-Fluoropolymer, conventional or linear polyethylene,
               polycarbonate, or polypropylene, 500-1000 mL

        6.1.2   Cleaning—Bottles are cleaned with liquid detergent and thoroughly rinsed with reagent
               water.  They are then heated to 50-60°C in concentrated reagent grade HNO3 for at
               least 2 h. The bottles are rinsed with reagent water, then immersed in a hot (50-60°)
               bath of IN trace metal  grade HC1 for at least 48 h. The bottles are then thoroughly
               rinsed with reagent water and filled with 0.1 % (v/v) ultrapure HC1 and double-bagged
               in new polyethylene zip-type bags  until needed.

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, noncontaminating material suitable for holding concentrated HNO3 and
               dilute HC1

        6.2.2   Panel immersion heater, all-fluoropolymer coated, capable of maintaining a
               temperature of 60-75°C in a vat of the size used

        6.2.3   Laboratory sink in class 100 clean  area, with high-flow reagent water for rinsing

        6.2.4   Clean bench, class 100, for drying  rinsed bottles.

6.3     Atomic absorption spectrophotometer (AAS)—Any atomic absorption spectrophotometer may
        serve as a detector. A bracket  is required to  hold the quartz atomizer in the optical path of the
        instrument.  Table 1 gives typical conditions  for the spectrophotometer.

        6.3.1   Electrodeless discharge lamp for measuring arsenic 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 la shows a schematic of the tube
               and bracket.

6.4     Equipment for 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

        6.4.2   Silicone rubber stopper septum (Ace  Glass #9096-32 or equivalent)
Draft, April 1995

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 Method 1632
        6.4.3   Four-way Teflon stopcock valve capable of switching of 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/min

        6.4.5   Silicone tubing—All glass-to-glass connections are made with silicone rubber sleeves.

 6.5     Equipment for cryogenic trap—Figure Ic 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 widemouth Dewar flask), which has been
               silanized and half-packed  with 15% OV-3 on Chromasorb® WAW-DMCS  (45-60
               mesh), and the ends of which have been 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 2 h.  At the end of this time,
                      inject two 25-uL aliquots of GC column conditioner (Silyl-8®, Supelco, Inc., or
                      equivalent) through the silicone tubing into the glass trap.  Return the trap to
                      the oven, with the He still flowing, for 24 h.

               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.
                      The wire-wrapped column is coated with approximately 2 mm of silicon
                      rubber caulking compound.

               6.5.3.3 The trap is connected by silicone rubber tubing to the output of the reaction
                      vessel.  The output side of the trap is connected by  6-mm diameter 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 uL  to
        5.0 mL.
10                                                                               Draft, April 1995

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                                                                                     Method 1632
 6.8     Analytical balance capable of weighing to the nearest 0.01 gram


 7.0   Reagents and Standards

 7.1     Reagent water—Water demonstrated to be free from As and potentially interfering substances
        at the MDL.  Prepared by distillation, deionization, reverse osmosis, anodic/cathodic stripping
        voltammetry, or other technique that removes As and potential interferant(s).

 7.2     Hydrochloric acid—Trace-metal purified reagent HC1.

 7.3     6M hydrochloric acid—Equal volumes of trace metal grade concentrated HC1 (Section 7.2) and
        reagent water (Section 7.1) are combined to give a solution approximately 6M in HC1.

 7.4     Nitric acid—Trace-metal  purified reagent HNO3

 7.5     10% nitric acid—Nitric acid  (HNO3):  10%  wt, Seastar, or equivalent.

 7.6     Sodium borohydride solution-4 g of >98% NaBH4 (previously analyzed and shown to be free
        of measurable arsenic) are dissolved in  100  mL of 0.02 M NaOH solution.  This solution is
        stable for only 8-10 h, and must be made fresh daily.

 7.7     Liquid nitrogen for cooling the cryogenic trap

 7.8     Helium—Grade 4.5 (standard laboratory grade) helium.

 7.9     Hydrogen—Grade 4.5 (standard laboratory grade) hydrogen.

 7.10    Air—Grade 4.5 (standard laboratory grade) air.

 7.11    QC  sample concentrate—From a source different than the one used to prepare calibration
        standards, prepare a QC sample concentrate  containing 1.50 ug/L As in reagent water (Section
        7.1) preserved with sufficient HNO3 to bring the pH to <2.

 7.12    Arsenic Standards

        7.12.1  Stock standard solution (1000 mg/L)—Either procure A2LA-certified aqueous
               standards from a supplier and verify by comparison to a second standard from a
               separate source, or dissolve 1.320 g  of arsenic trioxide  (As2O3) in 100 mL of reagent
               water (Section 7.1) containing 4 g NaOH.  Acidify the  solution with 20 mL
               concentrated HNO3 and dilute to 1.0 liter.
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 Method 1632
                       9.1.2.2.2       A listing of metal measured (As), 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
                                      (b) Calibration verification
                                      (c) Initial  precision and recovery (Section 9.2)
                                      (d) Analysis of blanks
                                      (e) Accuracy assessment

                       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
                                      (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
               9.5 describes the required types, procedures, and criteria for analysis of blanks.

        9.1.4   The laboratory shall spike  at least 10% of the samples with As to monitor method
               performance.  Section 9.3 describes this test. When results of these spikes indicate
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                                                                                      Method 1632
                atypical method performance for samples, an alternative 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 for regulatory compliance purposes.

        9.1.5   The laboratory shall, on an ongoing basis, demonstrate through calibration verification
                and through analysis of the ongoing precision and recovery aliquot that the analytical
                system is in control.  Sections 9.6 and 10.2 describe these 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 As, the analyst shall
                determine the MDL 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  that is no more than one-tenth the regulatory
                compliance  level or that is less than 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 analyst shall perform the following operations.

                9.2.2.1  Analyze four aliquots of reagent water spiked with As at 0.015 ug/L according
                       to the procedures in this method.  Prepare these by diluting each of four 1.0-
                       mL  aliquots of the QC Sample Concentrate to 100  mL.  All digestion,
                       extraction, and concentration 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)  in each aliquot and the standard deviation(s)  of the recovery.

                9.2.2.3  Compare s and X 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 for As.  Correct the problem and
                       repeat the  test (Section 9.2.2.1).

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 (MSD) sample analyses
        on 10%  of the samples from each site being monitored, or at least one MS sample analysis
        and one  MSD 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.
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 Method 1632
        9.3.1    The concentration of the MS and MSD is determined as follows:

                9.3.1.1 If, as in compliance monitoring, the concentration of As in the sample is being
                       checked against a regulatory concentration limit, the spike must be at that limit
                       or at five times the background concentration, whichever  is  greater.

                9.3.1.2 If the concentration is not being checked against a regulatory limit, the
                       concentration must be at five times the background concentration or at five
                       times the ML in Table 1, whichever is greater.

        9.3.2    Assessing spike recovery

                9.3.2.1 Determine the background concentration (B) of As by  analyzing one sample
                       aliquot according to the procedures specified in this method.

                9.3.2.2 If necessary, prepare a matrix spiking concentrate  that  will produce the
                       appropriate level (Section 9.3.1) in the sample when the concentrate is added.

                9.3.2.3 Spike a second sample aliquot with the QC check sample concentrate (or, if
                       necessary, with the matrix spiking concentrate) and analyze  it to determine the
                       concentration after spiking (A).

                9.3.2.4 Calculate each percent recovery (P) as 100(A - B)/T, where T is the known
                       true 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, As has failed the
                acceptance criteria.

                9.3.3.1 If As has failed the acceptance criteria, analyze the ongoing precision and
                       recovery standard (Section 9.6).  If the OPR is within its respective limit
                       (Table 2), the analytical system is in control and the problem can be attributed
                       to the sample matrix.

                9.3.3.2 For samples that exhibit matrix problems, further isolate As  from the sample
                       matrix using chelation, extraction, concentration, hydride generation, or other
                       means, and repeat the accuracy test (Section 9.3.2).

                9.3.3.3 If the  recovery for As remains outside the acceptance criteria, the analytical
                       result  in the unspiked sample is suspect and may not be reported for regulatory
                       compliance purposes.

        9.3.4   Recovery for samples should be assessed  and records maintained.
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                                                                                    Method 1632
               9.3.4.1 After the analysis of five samples of a given matrix type (river water, lake
                      water, etc.) for which As passes the tests in Section 9.3.3, compute the average
                      percent recovery (R) and the standard deviation of the percent recovery (SR).
                      Express the accuracy assessment as a percent recovery interval from R - 2SR
                      to R + 2SR for each matrix. For example, if R - 90% and SR - 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 five
                      to ten new measurements).

9.4    Precision of matrix spike duplicates

       9.4.1   Calculate the relative percent difference (RPD)  between the MS and MSD according to
               the equation below using the concentrations found in the  MS  and MSD. Do not use
               the recoveries calculated in Section 9.3.2.4 for this calculation because the RPD of
               recoveries is inflated  when the background concentration  is near the spike
               concentration.
                                     RPD -
                                                (Dl+D2)/2
                      Where:
                      Dl  = concentration of the analyte in the MS sample
                      Dl  = concentration of the analyte in the MSD sample
       9.4.2   Compare the RPD with the limits in Table 2.  If the criteria are not met, the analytical
               system is judged to be out of control.  Correct the problem and reanalyze all samples
               in the sample set associated with the MS/MSD that failed the RPD test.

9.5    Blanks—Blanks are analyzed to demonstrate freedom from contamination.

       9.5.1   Laboratory (method) blank

               9.5.1.1 Prepare a 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 10 samples).  Analyze the blank immediately after analysis of the
                      OPR (Section 9.6) to demonstrate freedom from contamination.

               9.5.1.2 If As 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 fresh method blank reanalyzed.


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 Method 1632
                9.5.1.3 Alternatively, if a sufficient number of blanks (three minimum) are analyzed to
                       characterize the nature of a blank, the  average concentration plus two standard
                       deviations must be less than the regulatory compliance level.

                9.5.1.4 If the result for a single 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 for 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 for regulatory compliance purposes.

        9.5.2   Field blank

                9.5.2.1  Analyze the field blank(s) shipped with each set of samples (samples collected
                       from the same site at the same time, to a maximum of 10 samples).  If the
                       samples are filtered for the determination of dissolved As, the field blank shall
                       be filtered as well. Analyze the blank  immediately before analyzing the
                       samples in the batch.

                9.5.2.2  If As or any potentially interfering substance is found in the field blank at a
                       concentration equal to or greater than the MDL (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
                       for regulatory compliance purposes.

               9.5.2.3  Alternatively, if a sufficient number of field blanks (three minimum) are
                       analyzed to characterize the nature of the field blank, the average concentration
                       plus two standard deviations must be less than the regulatory compliance level
                       or less than one-half  the level in the associated sample, whichever is greater.

               9.5.2.4  If contamination of the field blanks and associated samples is known or
                       suspected, the laboratory should communicate this to the sampling team so that
                       the source of contamination can be identified and corrective measures taken
                       before the next sampling event.

       9.5.3   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 equipment is free from contamination.  Two types of equipment
               blanks are required:  bottle blanks  and sampler  check blanks.

               9.5.3.1  Bottle blanks—After  undergoing  appropriate cleaning procedures (Section
                       11.4), bottles should be subjected to conditions of use to verify the
                      effectiveness of the cleaning procedures. A representative set of sample bottles
10
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                                                                                      Method 1632
                       should be filled with reagent water acidified to pH < 2 and allowed to stand
                       for a minimum of 24 h.  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 recleaned.

                9.5.3.2 Sampler check  blanks—Sampler check blanks are generated in the laboratory
                       or at the equipment cleaning contractor's facility by processing reagent water
                       through the  sampling devices using the same procedures that are used in the
                       field (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.

                       9.5.3.2.1       Sampler check blanks are generated by filling a large carboy or
                                      other container with reagent water (Section  7.2) and processing
                                      the reagent water 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.

                       9.5.3.2.2       The sampler check blank must be analyzed using the
                                      procedures in this method.  If As 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
                                      before the equipment may be used in the field.

                       9.5.3.2.3        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.

9.6     Ongoing precision and recovery

        9.6.1   Prepare a  precision and  recovery sample (laboratory-fortified method blank) identical
               to the initial precision and recovery aliquots (Section 9.2) with each sample batch
               (samples of the same matrix started through the extraction process on the same 12-
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Method 1632
               hour shift, to a maximum of 10 samples) by diluting a 1.0-mL aliquot of QC check
               sample concentrate to 100 mL with reagent water.

        9.6.2   Analyze the OPR aliquot before analyzing  the method blank and samples from the
               same batch.

        9.6.3   Compute the percent recovery of As in the OPR aliquot using the procedure given in
               this method.

        9.6.4   Compare the concentration 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, reprepare
               the sample  batch, and repeat the OPR test (Section 9.6).

        9.6.5   Add results that pass the specifications in Section 9.6.4 to initial and previous ongoing
               data for As in each matrix.  Update QC charts to form a graphic representation of
               continued laboratory performance. Develop a statement of laboratory accuracy in each
               matrix type by calculating the average percent recovery  (R) and the standard deviation
               of percent recovery  (SR). Express the accuracy as a recovery interval from R - 2SR to
               R + 2SR. For example, if R = 95% and SR - 5%, the accuracy is 85-105%.

9.7     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 by this
        method.

9.8     Depending on specific program requirements, field duplicates may be collected to determine
        the precision of the sampling technique. The relative percent difference (RPD) between field
        duplicates should be less than 20%.
10.0 Calibration and Standardization

10.1   Calibration—Calibrate at a minimum of three points, one of which must be the ML (Table  1),
       and another that must be near the upper end of the linear dynamic range.  Calibration is
       required before any samples or blanks are analyzed.

       10.1.1  External standard calibration

               10.1.1.1        Calculate the response factor (RF) for As in each CAL solution using
                             the following equation and the height or area produced.
20                                                                              Draft, April 1995

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                                                                                      Method 1632
                                                  (RJ
                                            RF  = — Z-
                          Where.

                          Rx = height or area of the signal for As
                          Cx = concentration of compound injected (\ig/L)
               10.1.1.2       Calculate the mean RF (M), the standard deviation of the RF (SD), and
                              the relative standard deviation (RSD) of the mean, where RSD = 100 x
                              SD/M.

               10.1.1.3       Linearity—If the RSD of the mean RF is less than 25% over the
                              calibration  range, an averaged response factor may be used.
                              Otherwise, a calibration curve must be used over the calibration range.

        Note:  The reagents used in the hydride generation process are likely to cause some
        absorbance in the absence of As.  Using a mean RF to quantitate samples will
        therefore result in decreasing accuracy with decreasing concentrations of As.  To
        avoid this, it is recommended that a calibration curve that is not forced through the
        origin be used in lieu of a mean RF, even if the  %RSD of the Rfs is less than 25%.

10.2    Calibration verification—Immediately after calibration, an initial calibration verification should
        be performed.  Adjustment of the instrument is performed until verification criteria are met.
        Only after these criteria are met may blanks and samples be analyzed.

        10.2.1  Verify the specificity of the instrument for As and adjust the wavelength or tuning
               until the resolving power specified in this method is met.

        10.2.2  Inject the mid-point calibration standard  (Section 10.1) or a dilution of the QC check
               sample concentrate with a concentration  near the midpoint of the calibration range.

        10.2.3  Compute the percent recovery of As using the mean response or calibration curve
               obtained in the initial calibration.

        10.2.4  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 10.2.2-10.2.4), or recalibrate the system according to this method and
               Section 10.1.
Draft, April 1995                                                                                21

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  Method 1632
         10.2.5  Calibration should be verified following every ten samples by analyzing the mid-point
                calibration standard.  If the recovery does not meet the acceptance criteria specified in
                Table 2, analysis must be halted, the problem corrected, and the instrument
                recalibrated.  All samples after the last acceptable calibration verification must be
                reanalyzed.
  11.0  Procedure

  11.1    Set the AA system up 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.

         Note:  Precision and sensitivity are affected by gas flow rates and these must be
 	individually optimized for each system, using the figures in Table 4 as an initial guide.

  11.2    To light the flame,  turn on all gases 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 5 min, 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.

 11.3    Place a known  volume of aqueous sample (up  to 70 mL) into the reaction vessel. If less than
         70 mL of sample is used, add  sufficient reagent water to result in a total volume of 70 mL.
         Add 5.0 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   Lower the trap  into a Dewar flask containing liquid nitrogen (LN2) and top the flask off with
        LN2 to a constant level.

 11.5   Add  10 mL of NaBH4 solution slowly (over a period of approximately 2 min)  through the
        rubber septum with  a disposable hypodermic syringe and begin timing the reaction.  After 7
        min, turn the stopcock on the four-way valve to bypass the reaction vessel and  pass helium
        directly to the trap.

 11.6   Quickly remove the trap from the LN2,  activate the heating coils to heat the trap and transfer
        line to 80°C, and begin recording output from the AA system.

 11.7    To ensure that all organic reduction products have  been desorbed from the trap, maintain the
        trap temperature at 80°C and keep He flowing through the trap for at least 3 min between
        samples.
22                                                                               Draft, April 1995

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                                                                                   Method 1632
 12.0  Data Analysis and Calculations

 12.1    Compute the concentration of As in ng/L (parts-per-trillion; ppt) using the calibration data
        (Section 10.1) according to the following equation:
                          where the terms are defined in Section 10.1.1

 12.2    If the concentration exceeds the linear dynamic range of the instrument, dilute the sample by
        successive factors of 10 lu until the concentration is within the linear dynamic range.

 12.3    Report results at or above the ML for As found in samples and determined in standards.
        Report all results for As found in blanks, regardless of level.

 12.4    Report results to one significant figure at or below the MDL, two significant figures between
        the MDL and ML, and three significant figures at or above the ML.

 12.5    Do not perform blank subtraction on  the sample results.
 13.0  Method  Performance

        Before this method was documented, an MDL study was conducted using the techniques
        described in the method. Additional method performance studies will be conducted in 1995,
        and the method will be revised as needed to reflect the results of those studies.

 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 by 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
Draft, April 1995                                                                             23

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Method 1632
       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 Department of Governmental Relations and
       Science Policy, 1155 16th Street NW, Washington DC 20036, 202/872-4477.
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 neutralized before being disposed, or must be 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 Department of Government
       Relations and Science Policy, 1155 16th Street NW, Washington, DC 20036.
 16.0  References

 16.1    Crecelius, E.A.; Bloom, N.S.; Cowan, C.E.; 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 for Determination 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 (1995).
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                                                                                   Method 1632
16.4   Patterson, C.C.; Settle, D.M. "Accuracy in Trace Analysis"; In National Bureau of Standards
       Special Publication 422; LaFleur, P.D., 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, Aug. 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.
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—Waters in the natural environment (e.g., rivers, lakes, streams, and other
       receiving waters), as opposed to effluent discharges.

17.2   Analytical Shift—All the 12-hour periods during which analyses are performed. The period
       begins with the purging of the OPR standard and ends exactly 12 hours later. All analyses
       both started and completed within this 12-hour period are valid.

17.3   Calibration Standard (CAL)—A solution prepared from a dilute mixed standard and/or stock
       solutions and used to calibrate the response of the instrument with respect to analyte
       concentration.

17.4   Equipment Blank—An aliquot of reagent water 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.
Draft, April 1995                                                                              25

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Method 1632
17.5   Field Blank—An aliquot of reagent water 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.

17.6   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.

17.7   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.  IPRs
       are performed before a method is used  for the first time and any time the method or
       instrumentation is modified.

17.8   Intercomparison Study—An exercise  in which samples are prepared and split by a reference
       laboratory, then analyzed by one or more testing laboratories and the reference laboratory.
       The intercomparison, with a reputable laboratory as the reference laboratory, serves as the best
       test of the precision and accuracy of the analyses at natural environmental levels.

17.9   Laboratory Blank—An  aliquot of reagent water 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 laboratory blank is used to determine if analytes or interferences
       are present in the laboratory environment,  the reagents, or the apparatus.

17.10  Laboratory Control Sample (LCS)—See Ongoing Precision and Recovery (OPR) Standard.

17.11  Laboratory Duplicates (LD1 and LD2)—Two aliquots of the same sample taken in the
       laboratory from the same sample bottle and analyzed separately using the referenced method.
       Analyses of LD1 and LD2 indicate precision associated with laboratory procedures, but not
       with sample collection, preservation, transportation, or storage procedures.

17.12  Laboratory Fortified Blank—See Ongoing Precision and Recovery (OPR) Standard.

17.13  Laboratory Fortified Sample Matrix—See Matrix Spike (MS) and Matrix Spike Duplicate
       (MSD).

17.14  Laboratory Reagent Blank—See Laboratory Blank.

17.15  Matrix Spike (MS) and Matrix Spike Duplicate (MSD)—Aliquots of an environmental
       sample to which known quantities of the analytes are added in the laboratory.  The MS and
26                                                                              Draft, April 1995

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                                                                                      Method 1632
        MSD are analyzed exactly like a sample.  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 MSD
        corrected for background concentrations.

 17.16  May—This action, activity, or procedural step is optional.

 17.17  May Not—This action, activity, or procedural step  is  prohibited.

 17.18  Method  Blank—See Laboratory Blank.

 17.19  Minimum Level (ML)—The  lowest level at which the entire analytical system gives a
        recognizable signal and acceptable calibration point.

 17.20  Must—This action, activity, or procedural step is required.

 17.21  Ongoing Precision and Recovery (OPR) Standard - A laboratory 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.

 17.22  Preparation Blank—See  Laboratory Blank.

 17.23  Primary Dilution Standard—A solution containing the analytes that is purchased or prepared
        from stock solutions  and diluted as needed to prepare  calibration solutions and other solutions.

 17.24  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.

 17.25  Reagent  Water—Water demonstrated to be  free from the metal(s) of interest and potentially
        interfering substances at the MDL for that metal in the referenced method.

 17.26  Should—This action, activity,  or procedural  step is  suggested but not required.

 17.27  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.
Draft, April 1995                                                                               27

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Method 1632
                       TABLE 1:  METHOD DETECTION LIMIT
                         (MDL) AND MINIMUM LEVEL (ML)
Method Detection Limit (MDL):
Minimum Level (ML):
0.002 ug/L
0.01000 ug/L
                         TABLE 2: METHOD QC CRITERIA
IPR Average Recovery (X)
IPR Standard Deviation(s)
Matrix Spike Recovery (P)1
OPR Recovery (P)1
MS/MSD RPD
Calibration Verification
59-143%
<42%
55-146%
55-146%
<20%
76-116%
                       OPR recovery required only it matrix spike recovery ooes not meet criteria
28
Draft, April 1995

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                                                                Method 1632
                 TABLE 3: TYPICAL SPECTROPHOTOMETER
                               SETTINGS
Parameter
EDL energy
EDL power
Wavelength
Slit width
Typical Setting
59
8 W
193.7 nm
0.7 nm
     TABLE 4: TYPICAL FLOWS AND PRESSURES FOR GASES IN THE HYDRIDE
                           GENERATION SYSTEM
          Gas
Flow Rate (mlVmin)
Pressure (lb/in2)
           He
           H2
           Air
      150
      350
      180
     10
     20
     20
Draft, April 1995
                                          29

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     Method 1632
     Figure 1.  Arsenic Speciation Apparatus:  (a) Quartz Cuvette Burner Tube, (b) Reaction Vessel, and
     (c) Schematic Diagram
Light Path
  Hi Input
 From Trap
      1C
      SCHEMATIC DIAGRAM
                                                              Wiie-wound
                                                              Pyrex U-Tob«
                                                              Hall-packed with
                                                              15% OV-3oo
                                                              Crwomanxti "W"
                                                                                 Chart FiecorOer Output
     30
                                                                                               Draft, April 1995

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