1、Designation: D3871 84 (Reapproved 2011)Standard Test Method forPurgeable Organic Compounds in Water Using HeadspaceSampling1This standard is issued under the fixed designation D3871; 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 () 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 arel
3、ess 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 knownconcen
4、trations 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 D2908.1.4 It is the users responsibility to assure the validity of thetest
5、 method for untested matrices.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of t
6、his standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in 8.5.5.1.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Re
7、agent WaterD2908 Practice for Measuring Volatile Organic Matter inWater by Aqueous-Injection Gas ChromatographyE355 Practice for Gas Chromatography Terms and Rela-tionships3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D1129 and Practice E355.3.2
8、Description of Term Specific to This Standard:3.2.1 purgeable organicany organic material that is re-moved from 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
9、the aqueous phase. These compoundsare then trapped in a column containing a suitable sorbent.After purging is complete, trapped components are thermallydesorbed onto the head of a gas chromatographic column forseparation and analysis. Measurement is accomplished with anappropriate detector.5. Signif
10、icance and Use5.1 Purgeable organic compounds, including organohalides,have been identified as contaminants in 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
11、gaschromatographic analysis (1 to 5).3This test method can beused to quantitatively determine purgeable organic 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 in
12、terfere with thechromatographic measurement. Likelihood of interference maybe decreased by using dissimilar columns or a more selectivedetector for the chromatographic step.7. Apparatus7.1 Purging DeviceCommercial devices are available forthis analysis. Either commercial apparatus or the equipmentde
13、scribed below may be used for this analysis. Devices usedshall be capable of meeting the precision and bias statementsgiven in 15.1.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Subs
14、tances in Water.Current edition approved May 1, 2011. Published June 2011. Originally approvedin 1979. Last previous edition approved in 2003 as D3871 84 (2003). DOI:10.1520/D3871-84R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
15、tm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The 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.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 aqueoussample while the sample is
17、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 allow sufficient space for foams to disperse. Inlet and exi
18、tports 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 controloccasional samples that foam excessively.7.2 TrapAshort s
19、ection 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 recommended and were used to collectprecision and bias da
20、ta. 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 mesh 2,6-diphenyl-p-phenylene oxidefollowed by 50 mm of 35
21、 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 Desorber consists of a trap heater and an auxiliarycarrie
22、r 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 chromatographs with a septum-type liquid-inletsystem.7.3.
23、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 seal. A plug is attached to one of the stemassemblies.7.3.1
24、.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 are used to provide the trap-backflush flow. This entirea
25、ssembly 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 assembled in accordance with Fig.A1.4 with internal volumes
26、 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 makes it easy to replace pluggedor dulled needles.7.3.2.2 The
27、 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 flame ionization, electrolytic conductivity, microcou-lomet
28、ric (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 used, theanalyst must demonstrate that the precision and bia
29、s 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 gasflow is 33 mL/min and a flame ionization detector is used.7
30、.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 Sampling Vials, glass, 45-mL, sealed with PTFE-facedsepta.4Vial c
31、aps 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 room temperature in a contaminant-freearea. When cool, th
32、e 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 water.7.6 Glass Syringe, 5-mL with two-way syringe valve and
33、150 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 Commit-tee onAnalytical Reagents of theAmerican Chemical Soci
34、ety.5Other 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 D1193, Type II, will be used in this test method. Analyzea
35、 5-mL aliquot of this water as described in Section 12 before4Pierce No. 13075 Screw Cap System Vials and 12722 Tuf-Bond Discs, PierceChemical Co., Rockford, IL, have been found satisfactory for this application.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society,
36、Washington, DC. For suggestions on the testing of reagents notlisted 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.D387
37、1 84 (2011)2preparing standard solutions. If the blank sample producesinterferences for the compounds of interest, purge it free ofvolatile contaminants with purge gas (8.9) before using.8.3 Dechlorinating AgentGranular sodium thiosulfate orascorbic acid.8.4 Trap Packings660/80 mesh chromatographic
38、grade2,6-diphenyl-p-phenylene oxide and 35 to 60 mesh silica gel.7Other 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 volumetricflask wit
39、h 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 drops ofone reference material to the flask, then reweigh. B
40、e 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 and volatile, prepare concentrated solutions ina hood. It is
41、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 temperaturebefore use.NOTE 1Standard solutions prepared in me
42、thyl 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 follows.8.6.1 Fill a 100-mL volumetric flask approximately three
43、fourths 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 stock solutions, dilute to themark with solvent and mix tho
44、roughly. 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 check sample by dosing20.0 L of the working standard solution
45、(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 mix. Prepare a freshinternal standard dosing solution daily
46、. 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 organic materials that may be present in the purge gasor laborator
47、y 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 has been chlorinated, add 1 to 2 mg ofdechlorinating agent t
48、o 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. If an aluminum foil disk is to be used, place itover the se
49、ptum. 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. 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. Calib
