1、Designation: D 3871 84 (Reapproved 2003)Standard 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 of revision
2、, 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 mostpurgeable organic compounds that boil below 200C and a
3、reless than 2 % soluble in water. It covers the low g/L to lowmg/L concentration range (see Section 15 and Appendix X1).1.2 This test method was developed for the analysis ofdrinking water. It is also applicable to many environmental andwaste waters when validation, consisting of recovering knowncon
4、centrations of compounds of interest added to representa-tive matrices, is included.1.3 Volatile organic compounds in water at concentrationsabove 1000 g/L may be determined by direct aqueousinjection in accordance with Practice D 2908.1.4 It is the users responsibility to assure the validity of the
5、test method for untested matrices.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limita
6、tions 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-Injection Gas Chromatography3E 35
7、5 Practice for Gas Chromatography Terms and Rela-tionships43. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129 and Practice E 355.3.2 Description of Term Specific to This Standard:3.2.1 purgeable organicany organic material that is re-moved from
8、 aqueous solution under the purging conditionsdescribed in this test method (10.1.1).4. Summary of Test Method4.1 An inert gas is bubbled through the sample to purgevolatile compounds from the aqueous phase. These compoundsare then trapped in a column containing a suitable sorbent.After purging is c
9、omplete, trapped components are thermallydesorbed onto the head of a gas chromatographic column forseparation and analysis. Measurement is accomplished with anappropriate detector.5. Significance and Use5.1 Purgeable organic compounds, including organohalides,have been identified as contaminants in
10、raw and drinkingwater. These contaminants may be harmful to the environmentand man. Dynamic headspace sampling is a generally appli-cable method for concentrating these components prior to gaschromatographic analysis (1 to 5).5This test method can beused to quantitatively determine purgeable organic
11、 compoundsin raw source water, drinking water, and treated effluent water.6. Interferences6.1 Purgeable compounds that coelute with components ofinterest and respond to the detector will interfere with thechromatographic measurement. Likelihood of interference maybe decreased by using dissimilar col
12、umns or a more selectivedetector for the chromatographic step.7. Apparatus7.1 Purging DeviceCommercial devices are available forthis analysis. Either commercial apparatus or the equipmentdescribed below may be used for this analysis. Devices usedshall be capable of meeting the precision and bias sta
13、tementsgiven in 15.1.7.1.1 Glass Purging Device having a capacity of 5 mL isshown in Fig. A1.1. Construction details are given in AnnexA1. A glass frit is installed at the base of the sample reservoirto allow finely divided gas bubbles to pass through the aqueous1This test method is under the jurisd
14、iction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved Jan. 10, 2003. Published January 2003. Originallyapproved in 1979. Last previous edition approved in 1995 as D3871 84 (1995)e1.2
15、Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 11.02.4Annual Book of ASTM Standards, Vol 14.02.5The boldface numbers in parentheses refer to the references at the end of thistest method.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
16、, PA 19428-2959, United States.sample while the sample is restrained above the frit. Thesample reservoir is designed to provide maximum bubblecontact time and efficient mixing.7.1.2 Gaseous volumes above the sample reservoir are keptto a minimum to provide efficient transfer and yet large enoughto a
17、llow sufficient space for foams to disperse. Inlet and exitports are constructed from 6.4-mm (14-in.) outside diametermedium-wall tubing so that leak-free removable connectionscan be made using“ finger-tight” compression fittings contain-ing plastic ferrules. The optional foam trap is used to contro
18、loccasional samples that foam excessively.7.2 TrapAshort section of stainless steel or glass tubing ispacked with a suitable sorbent. Traps should be conditionedbefore use (Section 11). While other trap designs and sorbentmaterials may be used (see Section 12), the trap and sorbentdescribed here are
19、 recommended and were used to collectprecision and bias data. If another trap design or sorbentmaterial is used, these precision and bias statements should beverified. A suitable trap design is 150 mm long by 3.17-mmoutside diameter (2.54-mm inside diameter). The front 100 mmis packed with 60 to 80
20、mesh 2,6-diphenyl-p-phenylene oxidefollowed by 50 mm of 35 to 60-mesh silica gel. One trapdesign is shown in Fig. A1.2, with details in Annex A1. Thebody assembly acts as a seal for the exit end of the trap. Themodified stem assembly is used to seal the inlet end of the trapwhen it is not in use.7.3
21、 Desorber consists of a trap heater and an auxiliarycarrier gas source to backflush the trap at elevated temperaturesdirectly onto the gas-chromatographic column. Desorber 1(Fig. A1.3 and Annex A1) is dedicated to one gas chromato-graph, but Desorber 2 can be used as a universal desorber formany gas
22、 chromatographs with a septum-type liquid-inletsystem.7.3.1 Desorber 1 is attached directly onto the gas-chromatograph liquid-inlet system after removing the septumnut, the septum, and the internal injector parts. The modifiedbody assembly is screwed onto the inlet system using the PTFEgasket as a s
23、eal. A plug is attached to one of the stemassemblies.7.3.1.1 The assembled parts, simply called “the plug,” areused to seal the desorber whenever the trap is removed tomaintain the flow of carrier gas through the gas-chromatographic column.7.3.1.2 The flow controller, PTFE tubing, and stem assem-bly
24、 are used to provide the trap-backflush flow. This entireassembly 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 any gas chromatograph by piercing the gas-chromatographic liquid-inlet septum with the needle.7.3.2.1 The desorber is a
25、ssembled in accordance with Fig.A1.4 with internal volumes and dead-volume areas held to aminimum. The heat source is concentrated near the base of thedesorber so that the internal seals of the body assembly do notbecome damaged by heat. The use of a detachable needleassembly from a microsyringe mak
26、es it easy to replace pluggedor dulled needles.7.3.2.2 The flow controller, PTFE tubing, and stem assem-bly are used to provide the trap-backflush flow. This entireassembly is also used to provide gas flow to operate thepurging device.7.4 Gas Chromatograph equipped with a suitable detector,such as f
27、lame ionization, electrolytic conductivity, microcou-lometric (halide mode), flame photometric, electron capture, ormass spectrometer.7.4.1 The gas chromatographic conditions described beloware recommended and were used to obtain precision and biasdata (Section 15). If other column conditions are us
28、ed, theanalyst must demonstrate that the precision and bias achievedare at least as good as that presented in Section 15.7.4.2 Column is 2.4 m by 2.4-mm inside diameter stainlesssteel packed with a suitable packing. Glass or nickel columnsmay be required for certain applications. Helium carrier gasf
29、low is 33 mL/min and a flame ionization detector is used.7.4.3 Chromatograph Oven is held at room temperatureduring trap desorption, then rapidly heated to 60C and held for4 min. Finally, the temperature is programmed to 170C at8C/min and held for 12 min or until all compounds haveeluted.7.5 Samplin
30、g Vials, glass, 45-mL, sealed with PTFE-facedsepta.6Vial caps must be open-top screw caps to prevent vialbreakage. The vials, septa, and caps are washed with detergentand hot water and rinsed with tap water and organic free water.The vials and septa are then heated to 105C for1handallowed to cool to
31、 room temperature in a contaminant-freearea. When cool, the vials are sealed with septa, PTFE sidedown, and screw capped. Aluminum foil disks may be placedbetween the septa and screw cap to help minimize contamina-tion. Vials are maintained in this capped condition until justprior to filling with wa
32、ter.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 beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Com
33、mit-tee onAnalytical Reagents of theAmerican Chemical Society.7Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, Specifica-tion
34、D 1193, Type II, will be used in this test method. Analyzea 5-mL aliquot of this water as described in Section 12 beforepreparing standard solutions. If the blank sample producesinterferences for the compounds of interest, purge it free ofvolatile contaminants with purge gas (8.9) before using.6Pier
35、ce No. 13075 Screw Cap System Vials and 12722 Tuf-Bond Discs, PierceChemical Co., Rockford, IL, have been found satisfactory for this application.7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlist
36、ed by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D 3871 84 (2003)28.3 Dechlorinating AgentGranular sodium thiosulfate o
37、rascorbic acid.8.4 Trap Packings860/80 mesh chromatographic grade2,6-diphenyl-p-phenylene oxide and 35 to 60 mesh silica gel.9Other 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
38、.1 Fill a 10.0-mL ground glass-stoppered volumetricflask with approximately 9.8 mL of methyl alcohol.8.5.2 Allow the flask to stand unstoppered about 10 min oruntil 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
39、drops ofone reference material to the flask, then reweigh. Be sure thatthe drops fall directly into the alcohol without contacting theneck of the flask.8.5.5 Dilute to volume, stopper, then mix by inverting theflask several times.8.5.5.1 WarningBecause the reference materials arelikely to be toxic a
40、nd volatile, prepare concentrated solutions ina hood. It is advisable to wear rubber gloves and use anapproved respirator 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 t
41、emperaturebefore use.NOTE 1Standard solutions prepared in methyl alcohol are generallystable up to 4 weeks when stored under these conditions. Discard themafter that time has elapsed.8.6 Working Standard (approximately 100 g/mL)Prepare a working standard containing each compound to betested, as foll
42、ows.8.6.1 Fill a 100-mL volumetric flask approximately threefourths full of methanol or acetone.8.6.2 Pipet 1 mL of the stock solution (8.5) of eachcompound of interest into the flask, using subsurface addition.Stopper the flask except when actually transferring solutions.8.6.3 After adding standard
43、 stock solutions, dilute to themark with solvent and mix thoroughly. Immediately transferthis solution to a clean vial (7.5) by filling to overflowing andsealing with a septum, PTFE side down, and screw cap.8.7 Quality Check Sample (approximately 20 g/L)Justprior to calibration, prepare a quality ch
44、eck sample by dosing20.0 L of the working standard solution (8.6) into 100.0 mLof water.8.8 Internal Standard 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-mLvolumetric flask, dilute to volume, and
45、 mix. Prepare a freshinternal standard dosing solution daily. Dose the internalstandard solution into every sample and reference standardanalyzed. It is up to the analyst to choose internal standardcompounds appropriate to the analysis.8.9 Purge GasNitrogen or HeliumTake precautions toprevent organi
46、c materials that may be present in the purge gasor laboratory air from contaminating the sample. High-puritypurge gases (99.99 %) are desirable. Lower quality gases maybe used if impurities are removed, for example by molecularsieve or low-temperature cold traps, or both.9. Sampling9.1 If the water
47、has been chlorinated, add 1 to 2 mg ofdechlorinating agent to the sampling vial (7.5) before sam-pling. Whether chlorinated or not, fill the vial to overflowing sothat a convex meniscus forms at the top. Place a septum, PTFEside down, carefully on the opening of the vial, displacing theexcess water.
48、 If an aluminum foil disk is to be used, place itover the septum. Then seal the vial with the screw cap andinvert to verify the seal by demonstrating the absence of airbubbles.NOTE 2The sample should be headspace-free at this time. A smallbubble may form if the vial is stored more than a few hours.
49、Analyze thesample within a few hours if possible. If storage is necessary, maintain thesample temperature at 0 to 4C until analyzed. Retighten the screw capafter the sample is chilled. Storage over charcoal will minimize contami-nation. Data on compounds tested showed them to be stable for at least 15days.10. Calibration and Standardization10.1 Calibrate the system by analyzing replicate aliquots ofthe quality check sample (8.7), to which 5 L of the internalstandard dosing solution (8.8) have been added, as described inSection 12. Replicate analyses pe
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