ASTM D3871-84(2017) Standard Test Method for Purgeable Organic Compounds in Water Using Headspace Sampling.pdf

1、Designation: D3871 84 (Reapproved 2017)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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Specific precautionary statements are given in 8.5.5.1.1.7 This international standard was developed in accor-dance with internationally recogniz

7、ed principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relati

8、ng to WaterD1193 Specification for Reagent WaterD2908 Practice for Measuring Volatile Organic Matter inWater by Aqueous-Injection Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relation-ships3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer t

9、oTerminology D1129 and Practice E355.3.2 Definitions of Terms Specific to This Standard:3.2.1 purgeable organic, nany organic material that isremoved 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

10、the sample to purgevolatile compounds from 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 accompl

11、ished with anappropriate detector.5. Significance 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 f

12、or concentrating these components prior to gas1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved Dec. 15, 2017. Published December 2017. Origi

13、nallyapproved in 1979. Last previous edition approved in 2011 as D3871 84 (2011).DOI: 10.1520/D3871-84R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standa

14、rds Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decis

15、ion on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1chromatographic analysis (1-5).3This test method can be usedto quantitatively determine purgeable organic compounds inraw so

16、urce 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 columns or a more sele

17、ctivedetector 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 statementsgiven in 15.

18、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 aqueoussample while the sample is restrained above the frit. Th

19、esample 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 exitports are constructed from 6

20、.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 section of stainless steel or

21、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 data. If another trap design or

22、 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 to 60-mesh silica gel. One t

23、rapdesign 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 auxiliarycarrier gas source to backflush the

24、 trap at elevated temperaturesdirectly onto the gas-chromatographic column. Desorber 1(Fig. A1.3 and Annex A1) is dedicated to one gaschromatograph, but Desorber 2 can be used as a universaldesorber for many gas chromatographs with a septum-typeliquid-inlet system.7.3.1 Desorber 1 is attached direct

25、ly 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.7.3.1.1 The assembled parts, simply

26、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 entireassembly also provides gas flow

27、to operate the purging device.7.3.2 Desorber 2 (Fig.A1.4 and AnnexA1) may be attachedto any gas chromatograph by piercing the gas-chromatographicliquid-inlet septum with the needle.7.3.2.1 The desorber is assembled in accordance with Fig.A1.4 with internal volumes and dead-volume areas held to amini

28、mum. 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 flow controller, PTFE tubing, and s

29、tem 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-lometric (halide mode), flame photometric

30、, 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 bias achievedare at least as good as th

31、at 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.7.4.3 Chromatograph Oven is held at r

32、oom 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 caps must be open-top screw caps to p

33、revent 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, the vials are sealed with septa, PTFE

34、sidedown, and screw capped. Aluminum foil disks may be placed3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.4Pierce No. 13075 Screw Cap System Vials and 12722 Tuf-Bond Discs, PierceChemical Co., Rockford, IL, have been found satisfactory for this applic

35、ation.D3871 84 (2017)2between 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 and150 to 200 mm, 20-gage syringe needle.8. Reagents and Materials8.1 Purity o

36、f 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 Society.5Other grades may be used, provided it is first ascertained thatthe rea

37、gent 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 5-mL aliquot of this water as described in Section 12 beforepreparing stan

38、dard 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 grade2,6-diphenyl-p-phenyl

39、ene 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 with approximately 9.8 mL of

40、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. Be sure thatthe drops fall

41、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 advisable to wear rubber g

42、loves 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 methyl alcohol are generally

43、stable 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 threefourths full of methanol o

44、r 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 thoroughly. Immediately trans

45、ferthis 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 (8.6) into 100.0 mLof wate

46、r.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. Dose the internalstandar

47、d 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 laboratory air from contaminating t

48、he 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 to the sampling vial (7.5)

49、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 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. Analyze thesample within a few hou