THE ANALYSIS OF TRIHALOMETHANES  IN FINISHED

                              WATERS BY THE PURGE AND TRAP METHOD

                                          Method 501.1
    I/)
                             U.  S.  ENVIRONMENTAL  PROTECTION  AGENCY
                         ENVIRONMENTAL MONITORING  AND  SUPPORT LABORATORY
                                     CINCINNATI, OHIO   45268
                                         November 6,  1979
QD142.
U55
1979

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                                    Foreword

    This method has been prepared by the  staff of the Environmental
Monitoring and Support Laboratory - Cincinnati, at the request of the Office
of Drinking Water.  Comments  and suggestions offered by the Municipal
Environmental Research Laboratory,  the Technical Support Division, ODW, and
the Health Effects Research Laboratory on the September 9, 1977, draft are
gratefully acknowledged.

    The procedure represents  the current  state-of-the-art, but as time
progresses improvements are anticipated.  Users are encouraged to identify
problems and assist in updating the method by contacting the  Environmental
Protection Agency, Environmental Monitoring and Support Laboratory,
Cincinnati, Ohio, 45268.

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                 The Analysis of Trihalomethanes In Drinking
                      Water by the Purge and Trap Method
1.  Scope
    1.1   This method (1) Is applicable 1n the determination of four
         tMhalomethanes, I.e. chloroform, dlchlorobromethane, dibromo-
         chloromethane, and bromoform in finished drinking water, raw source
         water, or drinking water In any stage of treatment.  The concen-
         tration of these four compounds is totaled to determine total
         trihalomethanes (TTKM).
    1.2   For compounds other than the above-mentioned trihalomethanes, or
         for other sample sources, the analyst must demonstrate the useful-
         ness of the method by collecting precision and accuracy data on
         actual samples as described (2).
    1.3   Although the actual detection limits are highly dependent upon the
         gas chromatographic column and detector employed, the method can be
         used over a concentration range of approximately 0.5 to 1500 micro-
         grans per liter.
    1.4   Well in excess of 100 different water supplies have been analyzed
         using this method.  Supplementary analyses using gas chromatography
         mass spectrometry (GC/MS) have shown that there is no evidence of
         interference in the determination of trihalomethanes (3).  For this
         reason, it 1s not necessary to analyze the raw source water as is
         required with the Liquid/Liquid Extraction Method  (4).
2.  Summary
    2.2  Trihalomethanes are extracted by an inert gas which  is bubbled
         through .the aqueous sample.  The trihalomethanes,  along with other

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     If any trihalomethane  is  noted  in  the method blank in excess of 0.4
     ug/1, ths  analyst  should  change the purge gas source and regenerate
     the molecular  sieve  ourge gas filter.  Subtracting the blank values
     is not recommended.  The use of  nqn-TFE plastic tubing, non-TFE
     thread.sealants, or  flow  controllers with rubber components should
     bo avoided since such  materials generally.out-gas organic compounds
     which will be  concentrated.in the .trap during the purge operation.
     Such out-gasing problems  are common whenever new equipment is put
     into service;  as time  progresses, minor out-gasing problems
     generally cure themselves.
3.2  Several instances  of accidental sample contamination have been
     noted and attributed to diffusion  of volatile organics through the
     septum seal and into the  sample during shipment and storage.  The
     sample blank is used as a monitor for this problem.
3.3  For compounds  that are not efficiently purged, such as bromoform,
     small variations in  sample volume, purge time, purge flow rate, or
     purge temperature  can  affect the analytical result.  Therefore,
     samples and standards  must be analyzed under identical conditions.
3.4  Cross-contamination  can occur whenever high-level and low-level
     samples are sequentially  analyzed.  To reduce this likelihood, the
     purging device and sample syringe  should be rinsed twice between
     samples with organic-free water.  Whenever an unusually concen-
     trated sample  is encountered, it is highly recommended that it be
     followed by a  sample blank analysis to ensure that sample cross
     contamination  dees not occur.   For samples containing large amounts
     of water soluble materials, it  may be necessary tc wash out the

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         organic constituents which exhibit low water solubility and a vapor
         pressure significantly^greater than water, are efficiently trans-
         ferred from the aqueous phase to" the gaseous phase.  These
         compounds.are swept from the purging device and are trapped In a
         short column containing a suitable* sorbent1."  After a predetermined
        -period of time, the trapped'components"are thermally desorbed and
         bacicf lushed onto'the'head-of argas chromatographic column and
         separated under programmed 'conditions/' Measurement Is accomplished
         with a halogen 'specific detector such as" electrolytic conductivity
         or-mlcrocbulometric tltratlon.
    2.3  Confirmatory analyses are performed using dissimilar columns, or by
         mass spectrometry (5).
    2.4  Aqueous standards and unknowns are extracted and analyzed under
         identical conditions In order to compensate for extraction losses.
    2.5  The total analysis time, assuming the absence of other organo-
         halides, 1s approximately 35 minutes per sample.
3.  Interferences
    3.1  Impurities contained in the purge gas and organic compounds, out-
         gasing from the plumbing ahead of the trap usually account for the
         majority of contamination problems.  The presence of such inter-
         ferences are easily monitored as a part of the quality control
         program.  Sample blanks are normally run between each set of
         samples.  When a positive trihalomethane response is noted in the
         sample blank, the analyst .should analyze a method blank.  Method
         blanks are run by charging the purging.device with organic-free
        .water and analyzing 1n the normal manner.

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         purging device with  a  soap  solution,  rinse with distilled water, and
         then dry  In  a 105°C  oven between  analyses.
    3.5  Qualitative  nils-identifications  are a  problem  1n using gas chromato-
         graphic analysis.  Whenever samples whose qualitative nature  1s
         unknown are  analyzed,  the following precautionary measures should be
         incorporated Into  the' analysis.
         3.5.1  Perform duplicate analyses using the two recommended columns
                (4.2.1  and  4.2.2} which  provide different retention order and
                retention times for  the  trlhalomethanes and other organo-
                halldes.
         3.5.2  Whenever possible, use GC/MS techniques which provide
                unequivocal qualitative  Identifications (5).
4.  Apparatus
    4.1  The purge and  trap equipment consists of three separate pieces of
         apparatus:   the purging device, trap, and desorber.  Construction
         details for  a purging  device and  an easily automated trap-desorber
         hybrid which has proven to  be exceptionally efficient and
         reproducible are shown in Figures 1 through 4 and described in'4,1.1
         through 4.1.3.  An earlier  acceptable version of the above-mentioned
         equipment is described 1n (1).
         4.1.1  Purging Device  - Construction  details  are given in Figure 1
                for an  all-glass 5 ml purging  device.  The glass frit
                Installed at  the base of the sample chamber allows finely
                divided gas bubbles  to pass through the sample while the

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       sample is restrained above the frit.  Gaseous volumes above
       the sample are kept to a minimum to eliminate dead volume
       effects, yet allowing sufficient .space for most foams to
       disperse.  The inlet and exit ports are constructed from
       heavy-walled 1/4-inch .glass tubi-ng sp-that Jeak-free
       removable connect ions^carj. be made .using "finger-tight"
       compression fittings containing Teflon ferrules.  The
       removable foam trap is used,to..control Camples that foam.
4/1.2  Trapping Device - The trap (Figure_2\.\s a short gas
       chromatographic column which at <35°C .retards the flow of
       the compounds of interest while venting the purge gas and,
       depending on which sorbent is used, much of the water vapor.
       The trap should be constructed with a low thermal mass so
       that it can be heated to 180°C in less than 1 minute for
       efficient desorption, then rapidly cooled to room tempera-
       ture for recycling.  Variations in the trap ID, wall
       thickness, sorfrents, sorbent packing order, and sorbent mass
       couTd adverse!/ affect the trapping and desorption efficien-
       cies for compounds-discussed in this text.  For this reason,
       it is important to faithfully reproduce the trap configu-
       rations recomme'nded in figure 2.  Traps containing Tenax
       only, or combinations of Tenax'and other sorbents are
       acceptable for this analysis.
4,1.3  Desorber assembly -Details for the desorber are shown in
       Figures 3, and 4.  With the 6-port valve in the Purge Sorb
       position (Figure 3), the effluent from the purging device

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       passes through the trap where the flew rate of the  organlcs
       1s retarded.  The GC carrier gas also passes through  the
       6-port valve and 1s returned to the GC.  With the 6-port
       valve 1n the Purge-Sorb position,, the operation of  the  GC 1s
       1n no way Impaired; therefore, routine liquid Injection
       analyses can be performed using the gas chromatograph.
       After the sample.has been purged, the 6-port valve  1s turned
       to the desorb position (Figure 4}.,.  In this configuration,
       the trap 1s coupled In series with the gas chromatographic
       column allowing the carrier gas to backflush the trapped
       materials Into the analytical column.  Just as the  valve 1s
       actuated, the power 1s turned on to the resistance  wire
       wrapped around the trap.  The power 1s supplied by  an
       electronic temperature controller.  Using this device,  the
       trap 1s rapidly heated to 180°C and then maintained at
       180°C with minimal temperature overshoot.  The trapped
       compounds are released as a "plug" to the gas chromatograph.
       Normally, packed columns with theoretical efficiencies  near
       500 plates/foot under programmed temperature conditions can
       accept such desorb Injections without altering peak
       geometry.  Substituting a non-controlled power supply,  such
       as a manually-operated variable transformer, will  provide
       nonreprodudble retention times and poor quantitative data
       unless Injection Procedure  (8.9.2) Is used.
4.1.4  Several Purge and Trap Devices are now commercially

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            available.  It 1s recommended that the following be taken
            into consideration If a unit Is to be purchased:
            a. Be sure that the unit Is completely compatible with the
               gas chromatograph to be used for the analysis.
            b. Use a-5-ml-purging device similar to that shown 1n Figure
               V.
            c:n Be sure-'the'"tenax portion of the trap meets or exceeds
              • the dimensions shown 1ri Figure 2.
            d:-With'the exception of s'ample' Introduction, select a unit
               that has as many of the purge trap functions automated as
               possible.
4.2 - Gas chromatograph - The chroraatograph must be temperature program-
     mable and equipped with-a hall'de specific detector.
     4.2.1  Column I Is an-unusually efficient column which provides
            outstanding separations for a wide variety of organic
            compounds.  Because of Its ability to resolve trihalo-
            methanes from other organodilorlne compounds, column I
            should be used as* the primary analytical column (see Table 1
            for retention data uslrtg this column).
            4.2.1.1  Column I parameters:  Dimensions - 8 feet long x
                     O.V Inch ID stainless steel or glass tubing.
                     Packing - IX SP-100Q on Carbopack-B (60/80} mesh.
                     Carrier Gas - helium at 40 ml/minute.  Temperature
                     program sequence:  45°C Isothermal for 3 minutes,
                     program at S°C/minute to 220°C then hold for 15
                     minutes or until all compounds have eluted.

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         NOTE: It has been found that during handling,
               packing, and programming, active sites are
               exposed on the Carbopack-B packing.  This
               results In tailing peak geometry and poor
               resolution of many constituents.  To correct
               this, pack the first 5 on of the column with
               3% SP-1000 on Chromosorb-W 60/80 followed by
               the Carbopack-B packing.  Condition the pre-
               coluinn and the Carbopack columns with carrier
               gas flow at 220°C overnight.  Pneumatic
               shocks and rough treatment of packed columns
               will cause excessive fracturing of the
               Carbopack.  If pressure 1n excess of 60 ps1
               Is required to obtain 40 ml/minute carrier
               flow, then the column should be repacked.
4.2.7.2  Acceptable column equivalent to Column I:
         Dimensions - 8 feet long x 0.1 Inch ID stainless
         steel or glass tubing.  Packing - 0.22 Carb'owax
         1500 on Carbopack-C (80/100) mesh.  Carrier Gas -
         helium at 40 ml/minute.  Temperature program
         sequence - 60°C  Isothermal for 3 minutes, program
         at 8°C/ minute to 160°C, then hold for 2
         minutes or until all compounds have eluted.
         NOTE: It has been found that during handling,
               packing, and programming, active sites are
               exposed on the Carbopack-C packing.  This

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                      results in poor resolution of constituents
                      and poor peak geometry.  To correct this,
                      place a 1 ft. 0.125 in. 00 x 0.1 1n. ID
                      stainless steel column packed with 3%
                      Carbowax 1500 on Chromosorb-W 60/80 mesh in
                      series before the Carbopack-C column.
                      Condition the precolumn and the Carbopack
                      columns with carrier gas flow at 190°C
                      overnight.  The two columns may be retained
                      1n series for routine analyses.  Trihalo-
                      methane retention times are listed 1n Table 1.
4.2.2  Column II provides unique organohalide-trihalomethane
       separations when compared to those obtained from Column I
       (see Figures 5 and 6).  However, since the resolution
       between various compounds 1s generally not as good as those
       with Column I, it Is recommended that Column II be used as a
       qualitative confirmatory column for unknown samples when
       GC/N5 confirmation is not possible.
       4.2.2.1  Column II parameters:  Dimensions - 6 feet long x
                0.1 Inch ID stainless steel or glass.  Packing -
                n-octane on Porisil-C (100/120 mesh).  Carrier Gas
                - helium at 40 cc/minute.  Temperature program
                sequence - 50°C Isothermal for 3 minutes, program
                at 6°/m1nute to 170°C, then hold for 4 minutes
                or until all compounds have eluted.  Trihalomethane
                retention times are listed in Table 1.

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    4.3  Sampling containers - 40 ml screw cap vials sealed with Teflon
         faced silicone septa.
         Vials and caps - Pierce #13075 or equivalent.
         Septa - Pierce #12722 or equivalent.
    4.4  Syringes - 5-ml glass hypodermic with luerlok tip (2 each).
    4.5  Micro syringes - 10, 100 ul.
    4.6  Micro syringe - 25 pi with a 2" x 0.006" ID needle-Hamilton #702N,
         or equivalent.
    4.7  2-way syringe valve with luer ends (3 each) Hamilton #86570-1FM1,
         or equivalent.
    4.8  Standard storage containers - 15 ml amber screw-cap septum bottles
         with Teflon faced silicone septa.
         Bottles and Caps - Pierce #19830, or equivalent.
         Septa - Pierce #12716, or equivalent.
5.  Reagents and Materials
    5.1  Porous polymer packing 60/80 mesh chromatographic grade Tenax GC
         (2,6-diphenylene oxide).
    5.2  Three percent OV-1 Chromosorb-W 60/80 mesh.
    5.3  l.OX SP-1000 on Carbopack-B (60/80 mesh) available from Supelco.
    5.4  n-Octane on Porasil-C (100/120 mesh) available from Waters
         Associates.
    5.5  Three percent SP-1000 on Chromosorb-W (60/80 mesh).
    5.6  Free and combined chlorine reducing agent - crystalline sodium
         thiosulfate, ACS Reagent Grade or sodium sulfite, ACS Reagent Grade.
    5.7  Activated carbon - Filtrasorb-200, available from Calgon
         Corporation, Pittsburgh, PA, or equivalent.

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    5.8  Organic-free water is defined as water free of interference when
         employed in the purge and trap analysis.
         5.8.1  Organic-free water is generated by passing tap water through
                a carbon filter bed containing about 1 Ih. of activated
                carbon.  Change the activated carbon bed whenever the
                concentration of any trihalomethane exceeds 0.4 ug/1.
         •5.8.2  A Millipore Super-Q Water System or its equivalent nay be
                used to generate organic-free water.
         5.8.3  Organic-free water may also be prepared by boiling water for
                15 minutes.  Subsequently, while maintaining the temperature
                at 90°C, bubble a contami.nant-fr.ee inert, gas through the
                water for one hour.  While still hat, transfer the water to
                a narrow-mouth screw-cap bottle with a Teflon seal.
         5.8.4  Test organic free water each day it is used by analyzing
                according to Section 8.
    5.9  Standards3
         5.9.1  Bromoform - 96% - available from Aldrich Chemical Company.
         5.9.2'  Bromodichl,orometha.ne 9756. - available from.Aldrich Chemical
                Company.
         5.9.3  Chlorodibromomethane - available from Columbia Chemical
                Inc., Columbia, S.C.
         5.9.4  Chloroform - 99% - available from Aldrich Chemical Company.
aAs a precautionary measure, all standards must be checked for purity by
boiling point determinations or GC/MS assays (5).

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5.10 Standard Stock Solutions
     5.10.1  Place about 9.8 ml of methyl alcohol into a ground glass
             stoppered 10 ml volumetric flask.
     5.10.2  Allow the flask to stand unstoppered about 10 minutes or
             until all alcohol wetted surfaces have dried.
     5.10.3  Weigh the flask to the nearest 0.1 mg.
     5.10.4  Using-a 100 ul syringe, immediately add 2 drops of the
             reference standard to the flask, then reweigh.  Be sure
             that the 2 drops fall directly into the alcohol without
             contacting the neck of the flask.
     5.10.5  Dilute to volume, stopper, then mix by inverting the flask
             several times.
     5.10.6  Transfer the solution to a dated and labeled 15 ml screw
             cap bottle with a Teflon cap liner.
             NOTE:  Because of the toxieity of trihalomethanes, it is
                    necessary to prepare primary dilutions in a hood.
                    It is further recommended that a NIOSH/MESA approved
                    toxic gas respirator be used'when the analyst
                    handles high concentrations of such materials.
     5.10.7  Calculate the concentration in micrograms per microliter
             from the net gain in weight.
     5.10.8  Store the solution at 4°C.
             NOTE:  All standard solutions prepared in methyl alcohol
                    are stable up to 4 weeks when stored under these
                    conditions;  They should be discarded after that
                    time has elapsed.

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5.11  Aqueous Calibration Standard Precautions
     5.11.1  In order to.prepare accurate aqueous standard solutions,
             the following precautions must be observed.
            .a.  Do ..not inject more-than 20 ul of alcoholic standards
                 into 100 .ml of organic-free water.
             b..  Use a 25 ul Hamilton 702N microsyringe or equivalent.
                 (Variations in needle-geometry will, adversely affect
                 the .-ability to deliver reproducible volumes of methan-
                 olic standards into water.)
             c.  Rapidly inject the alcoholic standard into the expanded
                 area of the filled volumetric flask.   Remove the needle
                 as fast as possible after.injection.
             d.  Mix aqueous standards by inverting  the flask three
                 times only.
             e.  Discard the .contents contained in the neck of the
                 fjask.   Fill  the sample syringe from  the standard
                 solution contained in the expanded  area of the flask as
                 directed in Section 8.5.
             f.  Never use pipets to dilute or transfer samples or
                 aqueous standards..
             g.  Aqueous standards when  stored with  a  headspace are not
                 stable  and.should be discarded after  one hour.
             h.   Aqueous standards can be stored according to Sections
                 6o4  and 8.6.
    5-. 11.2   Prepare,  from the standard  stock solutions, secondary
             dilution  mixtures.in methyl  alcohol  so  that a 20 ul

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                  injection Into 100 ml of organic-free water will  generate  a
                  calibration standard which produces a response close (+10%)
                  to  that of the sample (See 9.1).
         5.11.3   Purge and analyze the aqueous calibration standards  in  the
                  same manner as the samples..
         5.11.4   Othe*- calibration procedures (3).which.require the delivery
                  of  less than 20 u! of a methanol.ic standard into  a 5.0  ml
                  volume of water already contained in the sample syringe are
                  acceptable only if the-inathanolic standard is  delivered by
                  the  solvent flush technique (6),
    5.12 Quality  Check Standard (2.0 yg/1)
         5.12.1   From the  standard stock solutions,  prepare a secondary
                  dilution  in methyl alcohol  containing 10 ng/yl  of each
                  trihalomethane (See Section 5.10.8 Note).
         5.12.2   Daily,  inject 20.0 ul of this mixture into 100.0  ml  of
                  organic-free water and analyze according to Section  8.
6.  Sample Collection and  Handling
    5.1  The sample containers should have  a total  volume of at least 25 ml.
         6.1.1    Narrow mouth screw cap bottles with the  TFE fluorocarbon
                  face silicon septa cap liners are  strongly recommended.
    6.2  Sample Bottle Preparation
         6.2.1    Wash all  sample bottles and TFE seals in detergent.   Rinse
                  with tap  water and finally  with distilled water.
         6.2.2    Allow the bottles and seals to air  dry at room temperature,
                  then place in a 105°C oven  for one  hour, then  allow  to
                  cool  in an area known to be free of organics.

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             NOTE:  Do not heat the TFE seals for extended periods of
                    time (>1 Iiour) bacause the silicone layer slowly
                    degrades at 105°C.
     6.2.3   When cool,-seal the bottles using the TFE seals that will
             be used for-.sealIng the samples,
6.3  Sample:Stabilization - A chemical reducing agenc (Section 5.6) Is
     added-to., the sample-, iir order "to. arrest the formation of trihalo-
     methanes after"sampler collection (3, 7).  Do not add the reducing
     agent to samples whenjdata on maximum trlhalomethane formation is
     desired.  If chemical-stabilization'is employed, the reagent is
     also added to the blanks.  The-chemical agent (2.5 to 3 mg/40 ml)
     .is added to the empty sample bottles just prior to shipping to the
     sampling-'site.
6.4  Sample Collection
     6.4.1   Collect all samples in duplicate.
     6.4.2   Fill the.sample bottles in-such a manner that no air
             bubbles pass through the sample as the bottle is filled.
     6.4.3   Seal the bottles so that no air bubbles are entrapped in  it.
     6.4.4   Maintain the hermetic seal on the sample bottle until
             analysis.
     6.4.5   Sampling from a water tap.
             6.4.5.1 Turn on water and allow the system to flush until
                     the temperature of the water has stabilized.
                     Adjust the flow to about 500 ml/minute and collect
                     duplicate samples from the flowing stream.
     6.4.5   Sampling from -an open body of water.

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         6.4.6.1  F111  a 1-quart  wide-mouth bottle with  sample  from  a
                 representative  area.  Carefully fill duplicate
                 sample bottles  from the  1-quart bottle as  noted  In
                 6.4.2.
6.4.7    If  a  chemical  reducing  agent  has been  added to the sample
         bottles, fill  with  sample  just to overflowing, seal the
         bottle,  and shake vigorously  for 1 minute.
6.4.8    Sealing  practice for septum seal screw cap bottles.
         6.4.8.1  Open  the bottle and  fill to overflowing,  place  on
                 a level surface,  position the TFE side of the
                 septum seal upon  the convex sample meniscus  and
                 seal  the bottle by screwing the cap on tightly.
         6.4.8.2  Invert the sample and lightly tap the cap on a
                 solid surface.  The  absence of entrapped  air
                 Indicates  a successful-seal.  If bubbles  are
                 present, open  the bottle, add a few additional
                 drops of sample and  reseal the bottle as  above.
6.4.9    Blanks
         6.4.9.1  Prepare blanks 1n duplicate at the laboratory by
                 filling and sealing  sample bottles with organic-
                 free  water just prior to shipping the sample
                 bottles to the sampling site.
         6.4.9.2  If the sample  1s  to  be  stabilized, add an
                 Identical  amount  of  stabilization reagent to the
                 blanks.

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                 S.4.9-.3  Ship the blanks to and from the sampling  site
                          along with the sample bottles.
                 6.4.9.4  Store the blanks and the samples collected at a
                          given site (sample, set) together.  A sample set 1s
                          defined as all .the samples collected at a given
                          site .(I.e.-, at a water tretment plant, the
                          duplicate raw source waters, the duplicate
                          f 1n1 shed .waters, and the duplicate .blank samples
                          comprise the sample set).
    6.5. When samples have been collected according to Section 6, no measur-
         able loss of trlhalomethanes .has been detected over extended
         periods of storage time (3).  It Is recommended that all samples be
         analyzed within 14 days of collection.
7.  Conditioning Traps
    7.1  Condition newly p.acked traps overnight at 180°C with an Inert gas
         flow of at least 20 ml/rain.
         7.1.1   Vent the trap effluent to the room, not to the analytical
                 column.
    7.2  Prior to dally use, condition traps 10 minutes while backflushing
         at 180°C.  It may be beneficial to routinely condition traps
         overnight while backflushing at 180°C.
         7.2.1   The trap may be vented to the analytical column; however,
                 after conditioning, the column must be programmed  prior to
                 use.
8.  Extraction and Analysis
    8.1  Adjust the purge gas (nitrogen or helium) flow rate to 40  ml/min.

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8.2  Attach the trap  Inlet to the purging device.  Turn the valve to the
     purge-sorb position (Figure 3).
8.3  Open the syringe valve located on the purging device sample Intro-
     duction needle.
8.4  Remove the plungers from two 5 ml syringes  and attach a closed
     syringe valve to each.
8.5  Open the sample  bottle and carefully pour the sample Into one of
     the syringe barrels until 1t overflows.  Replace the syringe
     plunger and compress the sample.  Open the  syringe valve and vent
     any residual air while adjusting the sample volume to 5.0 ml.
     Close the  valve.
8.6  Fill the second  syringe  In an  Identical  manner from the same sample
     bottle.  This  second syringe  1s reserved for a duplicate analysis,
     1f necessary  (See  Section 9.3  and 9.4).
8.7  Attach the syringe-valve assembly to the syringe valve on the
     purging device.
8.8  Open the  syringe valve and  Inject the  sample  Into  the purging
     chamber.   Close both valves.   Purge the  sample for 11.0 +  .05
     alnutes.
8.9  After  the  !l-m1nute purge  time,  attach the  trap  to the.chromato-
     graph  (turn the valve  to the  desorb position)  and  Introduce the
     trapped materials  to the GC column  by rapidly heating the  trap to
     180°C  while backflushlng the trap with an  Inert  gas between 20
      and  60 ml/m1n for  4 minutes.
     8.9.1    If the trap can  be rapidly heated  to 180°C and maintained
              at this temperature,  the GC analysis can begin as  the

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              sample is desorbed, i.e., the column is at the initial
              45°C operating temperature.  The equipment described in
              Figure 4 will perform accordingly.
     8.9.2    With other types of equipment (see Section 4.1.4 and
              Reference.!) where the trap is not rapidly heated or is not
              heated in a reproducible manner, it may be necessary to
              transfer the contents of the trap into the analytical
              column at <30°C where it is once again trapped.  Once the
              transfer is complete (4 minutes), the column is rapidly
              heated to the initial operating temperature for analysis.
     8.9.3    If injection procedure 8.9.1 is used and the early eluting
              peaks in the resulting chromatogram have poor geometry or
              variable retention times, then Section 8.9.2 should be used.
8.10 After the extracted sample is introduced into the gas chromato-
     graph, empty the gas purging device using the sample introduction
     syringe, followed by two 5-ml flushes of organic-free water.  When
     the purging device is emptied, leave the syringe valve open
     allowing the purge gas to vent through the sample introduction
     needle.
8.11 Analyze  each sample and sample blank from the sample set in an
     identical manner (see" Section 6.4.9.4) on the same day,
8.12 Prepare  calibration standards from the standard stock solutions
     (Section 5.10) in organic-free water that are close to the unknown
     .in trihalomethane composition and concentration (Section 9.1).  The
     concentrations should be such that only 20 ul or less of the
     secondary dilution need be added to 100 ml of organic-free water to

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         produce a  standard  at  the  same  level as the  unknown.
    8.13 As an  alternative to Section 8.12, prepare a calibration curve for
         each trihalomethane containing  at  least 3 points, two of which must
         bracket the  unknown.
9.  Analytical  QualUy  Control
    9.1  Analyze the  2  ug/1  check sample daily-before any  samples are
         analyzed.  Instrument  status .checks and lower limit of detection
         estimations  based upon response factor calculations at five times
         the noise  level  are obtained
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             In organic-free water as described in Section 5.11.
9.4  Randomly select and analyze 10% of all samples in duplicate.
     9.4.1   Analyze all samples In duplicate which appear to deviate
             more than 30% from any established norm.
9.5  Maintain an up-to-date log on the accuracy and precision data
     collected in Sections 9.3 and 9.4.  If results are significantly
     different'than thosd cited in Section 1*1.1, the analyst should
     check out the entire analyses scheme to determine why the
     laboratory's precision and accuracy limits are greater.
9.6- Quarterly, spike an EMSL-Cincinnati trihalcmethane quality control
     sample into organic-free water and analyze.
     9.6.1   The results of the EMSL trlhalomethane quality control
             sample should agree within 20% of the true value for each
             trihalomethane.  If they do not then the analyst must check
             each step in the standard generation procedure to solve the
             problem (Section 5.9, 5.10, and 5.11).
9.7  Maintain a record of the retention times for each trihalomethane
     using data gathered from spiked samples and standards.
     9.7.1   Daily calculate the average retention time for each-
             trihalomethane and the variance encountered for the
             analyses.
     9.7.2   If individual trihalomethane retention time varies by more
             than 10% over an eight hour period or'does not fall with
             10% of an established norm, the system is "out of
             control."  The source of retention data variantion must be
             corrected before acceptable data can be generated.

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10.  Calculations
    10.1 Locate each trihalomethane in the sample chromatogram by comparing
         the retention time of the suspect peak to the data gathered In
         9.7.1.  The retention time of the suspect peak must fall within the
         limits established in 9:7.1 for single column identification.
    10.2 Calculate- the concentration of the samples by comparing the peak
         height or peak areas of the* samples to tha standard peak height
         (8.12).  Round off the data to the nearest ug/1 or two significant
         figures.
                                             *   
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11.  Accuracy and Precision
    11.1  One liter of organic-free water was spiked with the trihalomethanes
         and used to fill  septum seal vials which were stored under ambient
         conditions.  Tha  spiked samples were randomly analyzed over a
         2-week period of  time.  The single laboratory data listed in Table
         II- reflect the errors dua to- tha analytical procedure and storage.

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                                  REFERENCES


1.  Bellar, T.A., J.J. Lichtenberg, Determining Volatile Organics at the
    Microgram per Litre  Levels by Gas Chrcmatography, Journal AWWA., 66, 739
    (December 1974).

2.  "Handbook for Analytical Quality Control  1n Water and Wastewater
    Laboratories," Analytical Quality Control Laboratory, National
    Environmental .Research Center, Cincinnati, Ohio, June 1972.

3,,  Brass, H.J., et al.,  "National Organic Monitoring Survey:  Sampling and
    Purgeable Organic Compounds,, Drinking Water Quality Through Source
    Protection," R. B. Pojasek, Editor, Ann Arbor Science, p. 398, 1977.

4,  "The Analysis of Trlhalomethanes 1n Finished Water by the Liquid/Liquid
    Extraction Method, Method 501.2* Environmental Monitoring and Support
    Laboratory, Environmental Research Center, Cincinnati, Ohio,-45268, May
    15, 1979.

5.  Budde, W.L. and J.W.  Elchelberger, "Organics Analysis Using Gas
    Chromatography-Mass  Spectrometry," Ann Arbor Science, Ann Arbor,
    Michigan, 1979.

6.  White, L.D., et al.,  "Convenient Optimized Method for the Analysis of
    Selected Solvent Vapors in the Industrial Atmosphere," AIHA Journal,
    Vol. 31, p. 225, 1970.

7.  Kopfler, F.C., et al. "GC/MS Determination of Volatlles for the National
    Organlcs Reconnaissance Survey (NORS) or Drinking Water, Identification
    and Analysis of Organic Pollutants in Water," L. H. Keith, Editor, Ann
    Arbor Science, p. 87, 1976.

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                                   TABLE I

                      Retention Data for Trihalooiethanes
Trlhalomethane
Chloroform
Bromodl cfiloroiaettfane
Chiorodibromomethane
(Dlbromoch1oromethane)
Bromofonn
       Retention Time Minutes
                                               -Acceptable
                                             Alternative to
Column I
1* SP1000
Carbopack B
10.7
13.7
16.5
Column I
0.4X Carbowa
Carbopack C
8.2
10.8
13.2
19.2
15.7
•Column II
n-Octane
Porasll-C

  12.2
  14.7
  16.6

  19.2

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                                    TABLE II

                               Single Laboratory
                   Accuracy and Precision for Trihalomethanes
                                   Chloroform

Spike
yg/1
1.2
12.
119

Number
Samples
12
8
11

Mean
yg/i
1.2
11.
105
Precision
Standard
Deviation
0.14
0.16
7.9

Accuracy
X Recovery
100
92
88
  1.6
 16.
160
  2.0
 20.
196.
  2.3
 23.
231.
12
 8
11
12
 8
11
12
 8
11
Brorcod i ch 1 oromet h lane

          1.5
         15.
        145.

Chlorodibromomethane

          1.9
         19.
        185.

     Bromoform

         2.3
        23.
       223
 0.05
 0.39
10.2
 0.09
 0.70
10.6
 0.16
 1.38
16.3
 94
 94
 91
 95
 95
 94
100
100
 97

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-------
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-------
COlUMNt 0.5% CARBOWAX 1500 ON CARSOPACK-C
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-------
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                    FIGURE 6 CHROMATOGRAM OF ORGANOHALIDES

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