EPA-821-R-01-013
                                        January 2001
            Appendix to Method 1631
Total Mercury in Tissue, Sludge, Sediment, and Soil
       by Acid Digestion and BrCI Oxidation

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                                    Appendix to Method 1631
                       Total Mercury in Tissue, Sludge, Sediment, and Soil
                              by Acid Digestion and BrCl Oxidation1

Al.O  Scope and Application

A 1.1  This Appendix provides two sample preparation (digestion) procedures for oxidation of total
      mercury (Hg) in solid and semi-solid sample matrices. These procedures may be used in conjunction
      with EPA Method 163 IB: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor
      Atomic Fluorescence Spectrometry for determination of mercury in tissue, sludge, sediment, soil,
      industrial samples, and certified reference materials.

A1.2  The digestion procedures in this Appendix, in conjunction with Method 163 IB, allow determination
      of Hg at concentrations ranging from 1.0 to 5000 ng/g in solid and semi-solid matrices. Higher
      concentrations can be measured by selection of a smaller sample size and/or dilution of the digestate.

Al.3  The detection limit and minimum level of quantitation in this Method usually are dependent on the
      level of interferences rather than instrumental limitations. The method detection limit (MDL; 40
      CFR 136, Appendix B) for Hg has been determined to be in the range of 0.24 to 0.48 ng/g when no
      interferences are present (see Appendix Tables A3 and A4).  The minimum level of quantitation
      (ML) has been established as 1.0 ng/g. These levels assume a sample size of 0.5 g.

A 1.4  Because Hg concentrations in solids are typically 103 -  107 times higher than those found in aqueous
      samples, the sensitivity provided by the dual amalgam trap system and fluorescence detector
      described in Method 163 IB may be more sensitive than necessary, and a single trap and/or cold
      vapor atomic absorption spectroscopy (CVAAS) instrument may be adequate. These modifications
      are allowed under the equivalency provisions in EPA Method 163 IB. See Method 163 IB Section
      9.1.2. However, the dual amalgam trap system and fluorescence detector provide greater sensitivity
      and specificity in the presence of interferences,  and this system must be used to overcome
      interferences, if present, and to  achieve the sensitivity required, if necessary.

A2.0  Summary

A2.1  Digestion I—This procedure is preferred for matrices containing organic materials, such as sludge
      and plant and animal tissues, because the  organic matter is completely destroyed. In this procedure,
      a 0.2 - 1.5 g sample is digested with HNO3/H2SO4.  The digestate is diluted with BrCl solution to
      destroy the remaining organic material.

A2.2  Digestion II—This procedure is preferred for geological materials because of rapid and complete
      dissolution of cinnabar (HgS), which is otherwise more slowly attacked by the BrCl in Digestion I.
      In this procedure, a 0.5 - 1.5  g sample is digested with aqua regia (HC1/HNO3) to solubilize
      inorganic  materials.

A2.3  The Hg concentration in the digestate is determined using EPA Method 163 IB.
        1       Based on a standard operating procedure provided by Frontier Geosciences, Inc.

                                                2

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A3.0  Definitions

      See the Glossary at the end of Method 163 IB for definitions of the terms used in this Appendix.

A4.0  Contamination and Interferences

A4.1  For the complete recovery of mercury by Method 163 IB, all Hg in the sample must be converted to
      Hg(II). This is accomplished by free halogens present in the digestion step.

A4.2  In Digestion I, the addition of BrCl to the sample after it is fully solubilized HNO3/H2SO4 is critical
      to convert methyl Hg to Hg(II).  If the acid digestates are analyzed by Method 1631B without BrCl
      oxidation of tissues or geological media, a significant low bias may occur.

A4.3  In Digestion II, the reaction between concentrated HC1 and HNO3 in aqua regia generates nitrosyl
      chloride (NOC1) and free C12, both of which are very strong oxidants  for Hg-containing compounds
      including cinnabar (HgS) and precious metal amalgams that are not attacked by either acid alone.
      Aqua regia also converts all methyl  Hg to Hg(II). The aqua regia procedure in Digestion II leaches
      but does  not dissolve silicate minerals.  Crustal elements such as Fe, Al, Cr, Ba, and Si may not be
      quantitatively recovered in some media using this procedure.

A4.4  Digestates from both Digestion I and II contain free halogens and extreme caution must be taken to
      avoid purging these free halogens onto the gold sand traps (see Section 4.4.2 in Method 163 IB).
      Introduction of free halogens may be avoided by analyzing an aliquot of the sample digestate smaller
      than 5 mL (Appendix Section A12.3), and by pipetting aliquots of the digestate into bubbler water
      already containing SnCl2. The use of hydroxylamine hydrochloride to remove free halogens (as
      prescribed in Method  1631B for aqueous samples) is not needed for solid sample digestates; there is
      a sufficient amount of SnCl2 in the bubbler to reduce both Hg(II) and free halogens in digestate
      aliquots smaller than 5 mL.

A4.5  If iodized coal or other elemental carbon samples are to be analyzed,  the final acid concentration in
      the diluted sample must be greater than 40% (v/v), and  all carbon particles must be settled prior to
      analysis to avoid re-adsorption of Hg on the carbon and an ensuing low bias.

A5.0  Safety

      Observe  the safety precautions in Method 163 IB.

A6.0  Apparatus and Materials

A6.1  Digestion vessel—50-mL borosilicate Erlenmeyer flask, calibrated to 40 ± 0.5 mL; or any other
      acid-cleaned, flat-bottomed, borosilicate glass container calibrated to 40 ± 0.5 mL.

A6.2  Pressure  release digestion cap—Clear glass sphere or inverted fluoropolymer cone, approximately
      1.5 - 2.0  cm in diameter, initially cleaned by heating overnight in hot concentrated nitric acid.  The
      sphere or cone acts as a pressure release valve during gas evolution.  A common clear glass marble
      may be used as the sphere, or the cone may be custom manufactured. Colored glass marbles contain
      high levels of trace metals and must not be used.  The cap must completely cover the opening of the
      digestion vessel without falling in, yet not be so large as to risk falling off when slightly lifted by the
      gas pressure in the vessel.

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A6.3  Electric hot plate—A temperature controlled electric hot-plate capable of maintaining a temperature
      of 100-110°C. A commonly available fluoropolymer-coated pancake griddle is excellent for this
      purpose.  Do not use the griddle for heating flammable solvents.

A6.4  Dilution vessels—Volumetric flasks, glass, 25, 50.0, and 100.0 mL, cleaned per the procedures in
      Method 163 IB.

A6.5  Digestate storage vessel—VOA vial, glass, 40-mL, with fluoropolymer-lined cap, cleaned per the
      procedures in Method 163IB, or purchase I-Chem level 300, trace metal clean, with fluoropolymer-
      lined cap, or equivalent.

A6.6  Balance—Analytical, capable of weighing 1.0 mg.

A7.0  Reagents and Standards

A7.1  Reference matrices

      A7.1.1      Biota, including tissue and wet and dry municipal sludge—Chicken breast, skinless,
                  boneless, purchased at a local supermarket, or other tissue demonstrated to be free of
                  mercury at the MDL in Table Al

      A7.1.2      Soil, sediment, and other geological samples—Playground sand or other sand-like
                  material demonstrated to be free from mercury at the MDL in Table Al.

A7.2  Nitric acid (concentrated)—Reagent grade, containing less than 5 pg/mL Hg.  The HNO3 must be
      pre-analyzed for Hg before use.

A7.3  Sulfuric acid (concentrated)—Reagent grade, containing less than 5 pg/mL Hg. The H2SO4 must be
      pre-analyzed for Hg before use.

A7.4  HNO3/H2SO4 solution—In a fume hood, slowly add 300 mL of concentrated H2SO4 (Appendix
      Section A7.3) to 700 mL of concentrated HNO3 (Appendix Section A7.2) in a fluoropolymer bottle.

      Warning:  This mixture gets hot and emits caustic fumes.

A7.5  Dilute BrCl solutions—Use the concentrated (0.2N) BrCl solution in Section 7.6 of Method  163 IB
      to produce the following solutions:

      A7.5.1      0.07 N bromine monochloride solution—Dilute 300 mL of 0.2N BrCl solution to 1000
                  mL with reagent water in a fluoropolymer bottle.

      A7.5.2      0.02 N bromine monochloride solution—Dilute 100 mL of concentrated BrCl solution
                  to 1000 mL with reagent water in a fluoropolymer bottle.

A8.0  Sample Collection, Preservation, and Storage

A8.1  Samples are collected into acid-cleaned glass, polyethylene, or fluoropolymer jars. For all except
      very low level and high water content samples, polyethylene bags are also acceptable.  Dry solids

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      such as coal and ores may be collected and stored in heavy gauge paper pouches commonly used by
      geologists.

A8.2  Samples are collected using clean gloves.  Equipment is rinsed between samples to avoid
      cross-contamination.  In general, follow the sampling procedures in Method 1613B. The ultra-low
      level sampling procedures in EPA Method 1669 may not be necessary because Hg concentrations in
      solids are typically 103 - 107 times higher than those found in water samples.

A8.3  Sample shipment, storage, preservation, and holding times

      A8.3.1      Dry samples—Samples such as ores, coal, paper, and wood may be shipped
                  unrefrigerated and stored indefinitely in a cool, dry location known to have an
                  atmosphere that is low in mercury,

      A8.3.2      Biota samples—Samples containing biota, including wet and dry sludge, are shipped to
                  the laboratory at 0-4 °C and may be processed and stored in one of the following two
                  ways:

            A8.3.2.1     Biota samples large enough to sub-sample are homogenized to a fine paste with a
                        stainless steel mill, or finely chopped with stainless steel tools on an
                        acid-cleaned, plastic cutting board.  After homogenization, samples are stored
                        frozen at < -15 °C in an acid-cleaned glass or fluoropolymer jar. The jar should
                        be sized to be filled between  50 - 80% with sample.  Samples may be stored
                        frozen for a maximum of 1 year.

            A8.3.2.2     If not analyzed upon receipt at  the laboratory, biota samples may be lyophilized
                        (freeze-dried) prior to  homogenization and storage. Once lyophilized, biota
                        samples may be stored unrefrigerated in a low-mercury atmosphere for a
                        maximum of 1  year.

      A8.3.3      Wet sediment samples—Wet sediment samples are chilled and shipped to the
                  laboratory at 0-4  °C.  Because freezing and thawing may adversely affect homogeneity
                  by causing clumping and separation of the solids from the liquid, wet sediment samples
                  must be aliquoted and weighed at the  laboratory and prior to freezing if they are not
                  analyzed upon receipt. Wet sediment samples may be held for 1 year if aliquoted,
                  weighed, and frozen at < -15 °C. Sediment samples may be lyophilized and stored
                  unrefrigerated for  1 year in a low-mercury atmosphere if only total Hg will be
                  determined and no free elemental mercury (Hg°) is expected to be in the samples.

A9.0  Quality Control

A9.1  The quality control (QC) measures in Section 9 of Method 163 IB must be followed when analyzing
      samples using this Appendix. In addition, this Appendix requires method blanks. Descriptions of the
      modifications of the quality control measures in Method 163 IB that are required for application to
      solid and semi-solid matrices are provided below.

A9.2  Initial demonstration of laboratory capability

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      A9.2.1      Method detection limit (see Section 9.2.1 of Method 1631B)—The laboratory must
                  achieve an MDL that is less than or equal to the MDL listed in Table Al.

      A9.2.2      Initial precision and recovery (IPR; see Section 9.2.2 of Method 1631B)—Analyze four
                  aliquots of the appropriate reference matrix (see Appendix Section A7.1), each spiked
                  with 4.0 ng of Hg. This amount will be 8 ng/g for a 0.5 g sample. Calculate the
                  average percent recovery (X) and the RSD of percent recovery.  Compare X and RSD
                  with the corresponding IPR limits in Table Al.  If X and  RSD meet the acceptance
                  criteria, system performance is acceptable and analysis of samples may begin.  If,
                  however, RSD exceeds the precision limit or X is outside the recovery range,
                  performance of the analytical system is unacceptable. Correct the problem and repeat
                  the test.

A9.3  Matrix spike/matrix spike duplicate (MS/MSD; see Section 9.3 of Method 163 IB)

      9.3.1  Spike and analyze 1 out of every 10 samples of the same matrix type, in duplicate, at a
            concentration 2-5 times the background concentration of Hg in the unspiked sample or at the
            concentration in the IPR (Appendix Section A9.2.2), whichever is greater.  Calculate the
            percent recovery in each aliquot and the RPD between the aliquots. The individual recoveries
            and the RPD shall meet the MS/MSD recovery acceptance criteria in Table Al. If either
            recovery or the RPD does not meet the acceptance criteria, correct the problem  and repeat the
            test according to the procedures in Sections 9.3,4 and/or 9.3.5 of Method 1631B.

A9.4  Blanks (see Section 9.4 of Method 163 IB)

      A9.4.1      Because of the high concentrations of mercury in solid samples, as compared to
                  aqueous samples, field blanks (Section 9.4.3 of Method 163 IB) and sampler check
                  blanks (Section 9.4.4.2 of Method 1631B) are not required.  However, it may be
                  prudent to collect a sampler check blank the first time that a given set of sampling
                  equipment is used and whenever it is suspected to be contaminated.

      A9.4.2      Method blank—For each batch of 20 samples (Section 9.1.7 of Method 163 IB), digest
                  and analyze a method blank using the most appropriate reference matrix  (Appendix
                  Section A7.1). The laboratory may process a greater number of method  blanks, if
                  desired, and average the results. The method blank must include all sample processing
                  steps; e.g., homogenization (Appendix Section A8.3.2.1). The concentration of
                  mercury in the method blank, or the average of multiple method blanks, must meet the
                  QC acceptance criteria in Table Al; otherwise, the source of contamination must be
                  eliminated and the batch reanalyzed.

A9.5  Ongoing precision and recovery (OPR; see Section 9.5 of Method 1631B)—The OPR (laboratory
      control sample) for solid and semi-solid samples is test of the entire analytical system  and includes
      all sample processing procedures; e.g., homogenization (Appendix Section A8.3.2.1) and digestion
      (Appendix Section Al 1.1  or Al 1.2).

      A9.5.1      Analyze an aliquot of the appropriate reference matrix (see Appendix Section A7.1),
                  spiked at the concentration in the IPR (Appendix Section A9.2.2). Calculate the
                  percent recovery.

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      A9.5.2      Compare percent recovery with the OPR limit in Table Al.  If percent recovery meets
                  the acceptance criteria, system performance is acceptable and analysis of samples and
                  blanks may continue. If, however, percent recovery is outside of the acceptance range,
                  analytical system performance is unacceptable.  Correct the problem and repeat the test
                  according to Section 9.5.2 of Method 1631B.

A9.6  Quality Control Sample (QCS) - Many certified reference  materials (CRMs) are available for total
      mercury in plants, animals, fish, sediments,  soils, and sludge.  Recovery and precision for at least
      one QCS per batch of samples must meet the performance specifications provided by the supplier.

A9.7  Replicate samples—Some samples, particularly sediments, may be heterogeneous. Replicates of
      these samples should be analyzed to characterize this heterogeneity. Replicate samples may also be
      required by a specific program to assess the precision of the sample collection, transportation, and
      storage techniques. The relative percent difference (RPD)  between replicates should be less than
      30%.

A10.0      Calibration and Standardization

      A 10.1       Calibrate the CVAFS instrument system using the procedures in Section 10 of Method
                  1631B.  The concentration of the calibration  solutions is as given in Section 10.1.1.2 of
                  Method 1613B. The amount of Hg in these solutions will be 0.05, 0.5, 2.5, 5.0,  and
                  10.0 ng.

      A10.2       Calibration verification (VER)—Calibration  of the CVAFS instrument system must be
                  verified periodically using aqueous standards. In Method 163IB, the OPR is used for
                  this verification because the standards are added to water (see Sections 10.2 and 9.5 of
                  Method 163 IB). In contrast, the OPR in this Appendix (Appendix  Section A9.5) is
                  used to demonstrate that the end-to-end analytical system remains in control. To avoid
                  confusion, the periodic verification of calibration in this Appendix is referred to as
                  "calibration verification" (VER).  The VER is a spiked reagent water sample (an
                  aqueous blank spike) and is used to determine that the CVAFS remains in control.

            A10.2.1     Prior to and after the analysis of 10 samples, verify calibration of the CVAFS
                        instrument system using the OPR test  in Sections 9.5.1 and 9.5.2 of Method
                        1631B. Record results as calibration verification (VER).

            A10.2.2     The requirements in Section 9.5.2 of Method 163 IB  must be met for sample
                        results to be valid.

All.O      Digestion

A11.1      Digestion I: Hot re-fluxing HNO3/H2SO4 digestion followed by BrCl oxidation—This
            procedure is intended for biota, wood, paper, tissue, municipal sludge, and other primarily
            organic matrices (excluding coal).  It does, however, give quantitative recovery for Hg on
            finely divided geological matrices such as sediments and soils.

      A11.1.1     Accurately weigh (to the nearest mg) an aliquot of sample directly into a tared digestion
                  vessel (Appendix Section A6.1).  For organic matter such as biota, weigh 0.2-0.4 gram;
                  for tissue (e.g., fish), plant material, or sludge, weigh 0.5-1.5 grams; for dried material

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                  such as wood, paper, and CRMs, weigh 0.2-0.4 gram.  The use of too much organic
                  material will consume all of the acid in the digestion, resulting in a low recovery.

      Al 1.1.2     To each sample, add 10.0 mL of HNO,/H2SO4 solution (Appendix Section A7.4).
                  Place the digestion vessel in an acid fume hood and loosely cap with a clean marble or
                  inverted fluoropolymer cone (Appendix Section A6.2), For wood, paper, or other dry
                  carbohydrates that can react violently with the HNO3/H2SO4 solution, allow the sample
                  to sit in the cold acid for at least 4 hours before heating.

      Al 1.1.3     After digesting at room temperature, place the digestion vessel on a hot plate in the
                  hood and slowly bring to a gentle boil by incrementally increasing the plate temperature
                  over a 1-hour period. If excessive sample  foaming occurs, bring to temperature more
                  slowly.  Reflux for 2-3 hours to fully oxidize remaining organic matter.  The mineral
                  portion of soil and sediment samples will not dissolve but will be effectively leached by
                  this digestion.

      Al 1.1.4     After the digestion is complete, bring to the calibration mark on the digestion vessel (40
                  ± 0.5 mL; Appendix Section A6.1) with 0.02 N BrCl solution (Appendix Section
                  A7.5.2) and mix thoroughly.  Shake the sample/BrCl solution to homogenize, and allow
                  to sit at least 4 hours prior to analysis to oxidize remaining dissolved methyl Hg.
                  Analyze the oxidized digestate per Appendix Section A12.0.

      Note: Some highly organic matrices will require higher levels of BrCl (Appendix Section
      A7.5.1) and longer digestion times or elevated temperatures. The amount of reagent added to
      a sample must be the same as the amount added to the reagent blank to detect contamination
      in the reagents, and to the method blank and the OPR to demonstrate that mercury can be
      recovered quantitatively. BrCl oxidation must be continued until it is complete.

Al 1.2      Digestion II: Cold aqua regia followed by BrCl oxidation—This procedure is intended for
            coal, ores, sediments, soils, and other geological media.  It does, however, give quantitative
            recovery for Hg on finely divided biological media such as tissues, paper, and wood, because
            the organic matrix is leached rather than dissolved. Solid, dry geological media such as rocks,
            ores, and coal must be pulverized using a contamination-free  mill prior to digestion.
            Otherwise, mercury will not be recovered from the interior of large particles.

      Al 1.2.1     Accurately weigh (to the nearest mg) an aliquot of the  sample directly into a tared
                  digestion vessel. For wet sediments and soils, weigh 0.5-1.5 grams; for dried materials
                  such as coal,  ores, and CRMs, weigh 0.5-1.0 gram.  To better assure homogeneity,
                  sediments and soils should be screened through a 2-mm plastic sieve to remove large
                  rocks and sticks before digestion.

      Al 1.2.2     In a fume hood, add 8.0 mL of concentrated HC1 (Method 163 IB Section 7.3), swirl,
                  and add 2.0 mL of concentrated HNO3 to the sample in the digestion vessel. Cap the
                  vessel with a clean glass marble or inverted fluoropolymer cone.  Allow to digest at
                  room temperature for at least 4 hours but preferably overnight.

      Al 1.2.3     For coal or other elemental carbon-containing sample,  dilute the digestate to the
                  calibration mark (40 ± 0.5 mL) with 0.07 N BrCl  solution and shake the flask to mix
                  thoroughly.  The addition of BrCl ensures that Hg will not re-adsorb to the carbon

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                  particles, producing low recoveries.  After dilution and shaking, allow the sample to
                  settle overnight, or centrifuge prior to analysis. Be sure that all fine-grained particles
                  are completely settled prior to analysis. This settling can be hastened by centrifuging
                  for 20 minutes at 3000 RPM or by filtering the sample through a 0.45-mm filter.
                  Analyze per Appendix Section A12.0,

      All .2.4     For other than coal or elemental carbon-containing samples, dilute the digestate to
                  volume (40 ± 0.5 mL) with reagent water so that the meniscus is at the calibration line
                  in the neck of the digestion vessel. Shake vigorously and allow settling until the
                  supernatant is clear prior to analysis. Analyze per Appendix Section A12.0.

Al 1.3      The diluted digestates may be stored up to one year in glass or fluoropolymer containers prior
            to analysis, or for future re-analysis, if needed,

A12.0      Digestate Analysis

      Diluted digestates are analyzed in a manner analogous to the analysis of standards by Method 163 IB
      (see Section 10.0 of Method 163 IB).

A12.1      Pipet a 0.01- to 5.0-mL volume of diluted digestate (Appendix Section All.1.4, Al 1.2.3, or
            All.2.4) directly into a bubbler containing approximately 100 mL of pre-purged SnQ2-
            containing water.

      Note: The volume of SnCl2-containing  water in the bubbler is not critical for the purpose of purging
      but is assumed to be 0.100 L for the purpose of calculating results (see Appendix Section A13.1.1).

A12.2      Purge the solution onto a gold trap for 20 minutes.  These conditions allow measurement of
            Hg concentrations in the range of 1 - 5,000 ng/g (parts per billion).

A12.3      Change the SnCl2-containing water in the bubbler after a total of 10 mL of digestate has been
            added.  For example, if 2 digestate aliquots of 5 mL each have been added to 100 mL of fresh,
            pre-purged, SnCl2-containing water, the SnCl2-containing water must be changed and 100 mL
            of fresh, SnCl2-containing water must be placed in the bubbler and purged for a minimum of
            10 minutes prior to addition of another digestate aliquot.

A12.4      For samples known or expected to contain  high Hg concentrations, further dilute (usually by a
            factor of 100) an aliquot of the diluted digestate with 0.02 N BrCl solution, and analyze a
            sub-aliquot.

A13.0      Data Analysis and Calculations

A13.1      Calculation of solid phase concentrations

      A13.1.1     The analytical system in Method 1631B will give analytical results in units of area (or
                  height) for the volume of diluted digestate analyzed. To calculate the solid phase
                  concentration, use the following equation:

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                       CHg = (A, - ABB) x V * d » 0.1 / (CFm x v x w)

           where:
                 CHg   =     concentration of mercury in the sample (ng/g wet weight)
                 A^    =     peak area (or height) for mercury in the sample
                 ABB   =     peak area (or height) for the average of the bubbler blanks
                 V    =     volume of diluted digestate (mL) (Appendix Sections Al 1.1.4, Al 1.2.3,
                             Al 1.2.4) = 40 mL
                 d     =     dilution factor(s); e.g., a factor of 100 in Appendix Section A12.4.
                 0.1   =     volume in bubbler (L) (Assumed per note in Appendix Section A12.1)
                 CFm  =     mean CF  from calibration (area (or height))/(ng/L) (Method 1613B
                             Section 10.1.1.4)
                 v     =     digestate volume analyzed (mL) (Appendix Section A 12.1)
                 w    =     sample weight (g) (Appendix Section Al 1.1.1 or Al 1.2.1)

      A13.1.2    If desired, determine the moisture content of a sample aliquot and use the dry weight as
                 "w" in the equation above,

A13.2      Reporting

      A13.2.1    Report results as required in Method 163 IB except use reporting levels and units
                 appropriate to solid samples (ng/g).

      A13.2.2    Reagent blank results and method blank results are reported separately and, if
                 requested or required, are subtracted from sample Hg concentrations.

A14.0      Method Performance

A14.1      This Appendix was developed in a single laboratory and validated in a single laboratory.
           Performance data from these  studies are summarized in Tables A2 through A7.

A15.0      References

1.     Development of Digestion Procedures for Determination of Mercury in Solid and Semi-solid
      Samples, Frontier Geosciences, available from EPA Sample Control Center DynCorp I&ET,
      Alexandria, VA 22304 (703-461-2100; SCC@dyncorp.com).

2.     Single Laboratory Validation of Appendix to Method 1631, June-July 1999, Brooks-Rand Ltd.,
      EPA Sample Control Center Episode Number 6236, DynCorp I&ET, Alexandria, VA 22304 (703-
      461-2100; SCC@dyncorp.com).
                                              10

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Table Al. Quality control acceptance criteria.
             Test
   Acceptance Criteria
      Spike concentration
 Calibration linearity

 Calibration verification (VER)
 MDL
 ML
 MS/MSD recovery

 MS/MSD precision

 IPR recovery
 IPR precision
 OPR recovery	
    <15%RSDofCF

        77-123%
       0.48 ng/g(li
        1 ng/g(2)
        70-130%

      < 30% RPD

        75-125%
      < 20% RSD
       70- 130%
  0.5, 5, 25, 50, andlOOng/L =
  0.05,0.5,2.5, 5.0, and 10.0 ng
        5 ng/L = 0.5 ng
            0.8 ng/g
 0.05 ng (lowest calibration point)
    2x background or level in
  IPR/OPR, whichever is greater
    2x background or level in
  IPR/OPR, whichever is greater
             4.0 ng
             4.0 ng
	4.0 ng	
 Method blank
< 0.4 ng or < O.lx sample,
   whichever is greater
(1) See Appendix Table A4
(2) Assuming a 0.5 g sample

Table A2. Method performance for biological samples and CRMs digested using hot re-fluxing HNO3
digestion plus BrCl dilution and Method 163 IB. Blanks and spikes were on three different instruments,
over a period of several weeks. Data provided by Frontier Geosciences.
Test/material
Method blanks
2.0 ng/g matrix spike
IRM-007 (sludge)
DOLT-2 (fish liver)
DORM-2 (fish muscle)
NIST-2796 (mussel)
n
24
28
3
7
11
12
Hg concentration (ng/g; ppb)
mean
0.25
1.90(3>
3,680
2,164
4,682
60.4
SD
0.13
0.22
150
161
386
6.7
certified'"
~
2.00
3,150
2,140
4,640
61.0
Performance
DL = 0.33 ng/g(2)
95%rec.; 11% RSD
117%rec.;4%RSD
101% rec.; 7%RSD
101%rec.;8%RSD
99% rec.; 11% RSD
(1) value provided by supplier of reference material
(2) detection limit = 2.5 x SD for 24 method blanks (2.5 = student's t @ 23 degrees of freedom)
(3) net recovered; background concentration (chicken breast) was 0.41 ng/g
                                              11

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Table A3. Method performance for geological samples and CRMs using cold aqua regia digestion and
Method 1631B. Data provided by Frontier Geosciences.
Test/material
Method blanks
0.5 ng/g blank spike
NIST-2709 (soil)
NIST- 1633 (fly ash)
NIST-2710 (soil)
IAEA-356 (sediment)
PACS-1 (sediment)
NIST- 1630 (coal)
NIST- 1632 (coal)
n
23
8
9
2
3
1
1
3
5
Hg concentration (ng/g; ppb)
mean
0.045
0.465
1393
163
30888
7152
4402
108
79.3
SD
0.037
0.079
111
3.0
2,692
—
...
5.0
7.0
certified0'
—
0.50
1,400
160
32,610
7.62
4,540
127*
78
Performance
DL = 0.09 ng/g(2)
MDL = 0.24 ng/g
100% rec.; 8% RSD
102% rec.; 2% RSD
95% rec.; 9% RSD
94% rec.
97% rec.
85% rec.; 5% RSD
102% rec.; 9% RSD
(1) value provided by supplier of reference material
(2) detection limit = 2.5 x SD for 24 method blanks (2.5 = student's t @ 23 degrees of freedom)

Table A4. Results of MDL Set 2 analyses (spiked with 0.24 ng; ~0.8 ng/g). Data provided by Brooks-
Rand.
Rep
1
2
3
4
5
6
7
Sample
Mass (g)
1.03
1.29
1.25
1.36
1.28
1.01
1.17
Measured Hg (ng)
0.39
0.50
0.48
0.53
0.49
0.39
0.45
Blank-corrected Hg
(ng)
0.13
0.23
0.22
0.26
0.23
0.12
0.19
*blank corrected
Sample Concentration
(ng/g)*
0.41
0.71
0.73
0.78
0.68
0.40
0.61
Average: 0.62 ng/g
Std. Dev.: 0.15 ng/g
MDL = 0.48
                                               12

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Table A5. Analyses of spiked catfish samples (spiked with 17 n
Replicate
1
2
3
4
Sample Mass (g)
1.02
1.21
0.97
1.17
Measured Hg
(ng)
30.1
31.6
31.4
23.4
^ofHg). Data provided by Brooks-Rand
Recovered Hg
(ng)*
17.1
16.2
19.0
8.41
""background corrected
%Recovery*
99.3
93.7
110.2
48.7
Average: 88%
Std. Dev.: 27%
Table A6. Analyses of spiked powdered egg yolk (spiked with 2.9 ng of Hg).  Data provided by Brooks-
Rand.
Replicate
1
2
3
4
Sample Mass (g)
1.00
1.06
1.04
1.08
Measured Hg
(ng)
3.49
3.16
2.56
3.75
Recovered Hg*
(ng)
2.34
1.94
1.37
2.50
*background corrected
%Recovery
80.6
67
47.1
86.2
Average: 70%
Std. Dev.: 17%
                                              13

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