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2、 84 (Reapproved 2003)An American National StandardStandard Test Method forPurgeable Organic Compounds in Water Using HeadspaceSampling1This standard is issued under the fixed designation D 3871; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
3、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of most purgeable organic compounds that boil below
4、 200C and are less than 2 % soluble in water. It covers the low g/L to low mg/L concentration range (see Section 15 and Appendix X1).1.2 This test method was developed for the analysis of drinking water. It is also applicable to many environmental and waste waters when validation, consisting of reco
5、vering known concentrations of compounds of interest added to representa- tive matrices, is included.1.3 Volatile organic compounds in water at concentrations above 1000 g/L may be determined by direct aqueous injection in accordance with Practice D 2908.1.4 It is the users responsibility to assure
6、the validity of the test method for untested matrices.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bil
7、ity of regulatory limitations prior to use. Specific precau- tionary statements are given in 8.5.5.1.2. Referenced Documents2.1 ASTM Standards:D 1129 Terminology Relating to Water2D 1193 Specification for Reagent Water2D 2908 Practice for Measuring Volatile Organic Matter inWater by Aqueous-Injectio
8、n Gas Chromatography3E 355 Practice for Gas Chromatography Terms and Rela- tionships43. Terminology3.1 DefinitionsFor definitions of terms used in this test method, refer to Terminology D 1129 and Practice E 355.3.2 Description of Term Specific to This Standard:1 This test method is under the jurisd
9、iction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for Organic Substances in Water.Current edition approved Jan. 10, 2003. Published January 2003. Originally approved in 1979. Last previous edition approved in 1995 as D3871 84 (1995)
10、e1.2 Annual Book of ASTM Standards, Vol 11.01.3 Annual Book of ASTM Standards, Vol 11.02.4 Annual Book of ASTM Standards, Vol 14.02.3.2.1 purgeable organicany organic material that is re-moved from aqueous solution under the purging conditions described in this test method (10.1.1).4. Summary of Tes
11、t Method4.1 An inert gas is bubbled through the sample to purge volatile compounds from the aqueous phase. These compounds are then trapped in a column containing a suitable sorbent. After purging is complete, trapped components are thermally desorbed onto the head of a gas chromatographic column fo
12、r separation and analysis. Measurement is accomplished with an appropriate detector.5. Significance and Use5.1 Purgeable organic compounds, including organohalides, have been identified as contaminants in raw and drinking water. These contaminants may be harmful to the environment and man. Dynamic h
13、eadspace sampling is a generally appli- cable method for concentrating these components prior to gas chromatographic analysis (1 to 5).5 This test method can be used to quantitatively determine purgeable organic compounds in raw source water, drinking water, and treated effluent water.6. Interferenc
14、es6.1 Purgeable compounds that coelute with components of interest and respond to the detector will interfere with the chromatographic measurement. Likelihood of interference may be decreased by using dissimilar columns or a more selective detector for the chromatographic step.7. Apparatus7.1 Purgin
15、g DeviceCommercial devices are available for this analysis. Either commercial apparatus or the equipment described below may be used for this analysis. Devices used shall be capable of meeting the precision and bias statements given in 15.1.7.1.1 Glass Purging Device having a capacity of 5 mL is sho
16、wn in Fig. A1.1. Construction details are given in Annex A1. A glass frit is installed at the base of the sample reservoir to allow finely divided gas bubbles to pass through the aqueous5 The boldface numbers in parentheses refer to the references at the end of this test method.Copyright ASTM Intern
17、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1D 3871 84 (2003)sample while the sample is restrained above the frit. Thesample reservoir is designed to provide maximum bubble contact time and efficient mixing.7.1.2 Gaseous volumes above the sample reser
18、voir are kept to a minimum to provide efficient transfer and yet large enough to allow sufficient space for foams to disperse. Inlet and exit ports are constructed from 6.4-mm (14-in.) outside diameter medium-wall tubing so that leak-free removable connections can be made using“ finger-tight” compre
19、ssion fittings contain- ing plastic ferrules. The optional foam trap is used to control occasional samples that foam excessively.7.2 TrapA short section of stainless steel or glass tubing is packed with a suitable sorbent. Traps should be conditioned before use (Section 11). While other trap designs
20、 and sorbent materials may be used (see Section 12), the trap and sorbent described here are recommended and were used to collect precision and bias data. If another trap design or sorbent material is used, these precision and bias statements should be verified. A suitable trap design is 150 mm long
21、 by 3.17-mm outside diameter (2.54-mm inside diameter). The front 100 mm is packed with 60 to 80 mesh 2,6-diphenyl-p-phenylene oxide followed by 50 mm of 35 to 60-mesh silica gel. One trap design is shown in Fig. A1.2, with details in Annex A1. The body assembly acts as a seal for the exit end of th
22、e trap. The modified stem assembly is used to seal the inlet end of the trapwhen it is not in use.7.3 Desorber consists of a trap heater and an auxiliary carrier gas source to backflush the trap at elevated temperatures directly onto the gas-chromatographic column. Desorber 1(Fig. A1.3 and Annex A1)
23、 is dedicated to one gas chromato- graph, but Desorber 2 can be used as a universal desorber for many gas chromatographs with a septum-type liquid-inlet system.7.3.1 Desorber 1 is attached directly onto the gas- chromatograph liquid-inlet system after removing the septum nut, the septum, and the int
24、ernal injector parts. The modified body assembly is screwed onto the inlet system using the PTFE gasket as a seal. A plug is attached to one of the stem assemblies.7.3.1.1 The assembled parts, simply called “the plug,” are used to seal the desorber whenever the trap is removed to maintain the flow o
25、f carrier gas through the gas- chromatographic column.7.3.1.2 The flow controller, PTFE tubing, and stem assem- bly are used to provide the trap-backflush flow. This entire assembly also provides gas flow to operate the purging device.7.3.2 Desorber 2 (Fig. A1.4 and Annex A1) may be at- tached to an
26、y gas chromatograph by piercing the gas- chromatographic liquid-inlet septum with the needle.7.3.2.2 The flow controller, PTFE tubing, and stem assem-bly are used to provide the trap-backflush flow. This entire assembly is also used to provide gas flow to operate the purging device.7.4 Gas Chromatog
27、raph equipped with a suitable detector, such as flame ionization, electrolytic conductivity, microcou- lometric (halide mode), flame photometric, electron capture, or mass spectrometer.7.4.1 The gas chromatographic conditions described below are recommended and were used to obtain precision and bias
28、 data (Section 15). If other column conditions are used, the analyst must demonstrate that the precision and bias achieved are at least as good as that presented in Section 15.7.4.2 Column is 2.4 m by 2.4-mm inside diameter stainless steel packed with a suitable packing. Glass or nickel columns may
29、be required for certain applications. Helium carrier gas flow is 33 mL/min and a flame ionization detector is used.7.4.3 Chromatograph Oven is held at room temperature during trap desorption, then rapidly heated to 60C and held for4 min. Finally, the temperature is programmed to 170C at8C/min and he
30、ld for 12 min or until all compounds have eluted.7.5 Sampling Vials, glass, 45-mL, sealed with PTFE-faced septa. 6 Vial caps must be open-top screw caps to prevent vial breakage. The vials, septa, and caps are washed with detergent and hot water and rinsed with tap water and organic free water. The
31、vials and septa are then heated to 105C for 1 h and allowed to cool to room temperature in a contaminant-free area. When cool, the vials are sealed with septa, PTFE side down, and screw capped. Aluminum foil disks may be placed between the septa and screw cap to help minimize contamina- tion. Vials
32、are maintained in this capped condition until just prior to filling with water.7.6 Glass Syringe, 5-mL with two-way syringe valve and150 to 200 mm, 20-gage syringe needle.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it
33、 is intended that all reagents shall conform to the specifications of the Commit- tee on Analytical Reagents of the American Chemical Society.7Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy o
34、f the determination.8.2 Purity of WaterUnless otherwise indicated, Specifica- tion D 1193, Type II, will be used in this test method. Analyzea 5-mL aliquot of this water as described in Section 12 before preparing standard solutions. If the blank sample produces interferences for the compounds of in
35、terest, purge it free of volatile contaminants with purge gas (8.9) before using.7.3.2.1 The desorber is assembled in accordance with Fig. 6 Pierce No. 13075 Screw Cap System Vials and 12722 Tuf-Bond Discs, PierceA1.4 with internal volumes and dead-volume areas held to aminimum. The heat source is c
36、oncentrated near the base of the desorber so that the internal seals of the body assembly do not become damaged by heat. The use of a detachable needle assembly from a microsyringe makes it easy to replace plugged or dulled needles.Chemical Co., Rockford, IL, have been found satisfactory for this ap
37、plication.7 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United Sta
38、tes Pharmacopeia and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.2D 3871 84 (2003)8.3 Dechlorinating AgentGranular sodium thiosulfate orascorbic acid.8.4 Trap Packings860/80 mesh chromatographic grade2,6-diphenyl-p-phenylene oxide and 35 to 60 mesh silica gel. 9Oth
39、er packings may be needed for specific determinations.8.5 Stock SolutionsPrepare a stock solution (approxi- mately 2 mg/mL) for each material being measured, as follows:8.5.1 Fill a 10.0-mL ground glass-stoppered volumetric flask with approximately 9.8 mL of methyl alcohol.8.5.2 Allow the flask to s
40、tand unstoppered about 10 min or until all alcohol wetted surfaces dry.8.5.3 Weigh the unstoppered flask to the nearest 0.1 mg.8.5.4 Using a 100-L syringe, immediately add 6 drops of one reference material to the flask, then reweigh. Be sure that the drops fall directly into the alcohol without cont
41、acting the neck of the flask.8.5.5 Dilute to volume, stopper, then mix by inverting the flask several times.8.5.5.1 WarningBecause the reference materials are likely to be toxic and volatile, prepare concentrated solutions ina hood. It is advisable to wear rubber gloves and use an approved respirato
42、r when handling volatile toxic materials.8.5.6 Calculate the concentration in micrograms per millili- tre from the net gain in weight.8.5.7 Store the solutions at 4C. Warm to room temperature before use.NOTE 1Standard solutions prepared in methyl alcohol are generally stable up to 4 weeks when store
43、d under these conditions. Discard them after that time has elapsed.8.6 Working Standard (approximately 100 g/mL) Prepare a working standard containing each compound to be tested, as follows.8.6.1 Fill a 100-mL volumetric flask approximately three fourths full of methanol or acetone.8.6.2 Pipet 1 mL
44、of the stock solution (8.5) of each compound of interest into the flask, using subsurface addition. Stopper the flask except when actually transferring solutions.8.6.3 After adding standard stock solutions, dilute to the mark with solvent and mix thoroughly. Immediately transfer this solution to a c
45、lean vial (7.5) by filling to overflowing and sealing with a septum, PTFE side down, and screw cap.8.7 Quality Check Sample (approximately 20 g/L)Just prior to calibration, prepare a quality check sample by dosing20.0 L of the working standard solution (8.6) into 100.0 mLof water.8.8 Internal Standa
46、rd Dosing SolutionFrom stock stan- dard solutions prepared as in 8.5, add a volume to provide 1000g of each standard to 45 mL of water contained in a 50-mL volumetric flask, dilute to volume, and mix. Prepare a fresh internal standard dosing solution daily. Dose the internal standard solution into every sample and reference standard8 60 to 80 mesh Carbopack C coated with 0.2 % Carbowax 1500 proceded by 0.3 m of 60 to 80 mesh Chromsorb W-H.P., coated with 3 % Carbowax 1500, ava
