ASTM D6520-2018 Standard Practice for the Solid Phase Micro Extraction (SPME) of Water and its Headspace for the Analysis of Volatile and Semi-Volatile Organic .pdf

1、Designation: D6520 18Standard Practice forthe Solid Phase Micro Extraction (SPME) of Water and itsHeadspace for the Analysis of Volatile and Semi-VolatileOrganic Compounds1This standard is issued under the fixed designation D6520; the number immediately following the designation indicates the year o

2、foriginal adoption or, in the case of revision, 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 practice covers procedures for the extraction ofvolat

3、ile and semi-volatile organic compounds from water andits headspace using solid phase micro extraction (SPME).1.2 The compounds of interest must have a greater affinityfor the SPME-absorbent polymer or adsorbent or combinationsof these than the water or headspace phase in which theyreside.1.3 Not al

4、l of the analytes that can be determined by SPMEare addressed in this practice. The applicability of the absor-bent polymer, adsorbent, or combination thereof, to extract thecompound(s) of interest must be demonstrated before use.1.4 This practice provides sample extracts suitable forquantitative or

5、 qualitative analysis by gas chromatography(GC) or gas chromatography-mass spectrometry (GC-MS).1.5 Where used, it is the responsibility of the user to validatethe application of SPME to the analysis of interest.1.6 The values stated in SI units are to be regarded asstandard. No other units of measu

6、rement are included in thisstandard.1.7 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, health, and environmental practices and deter-mine the applicability of

7、 regulatory limitations prior to use.For specific hazard statements, see Section 12.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Gui

8、des and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD3370 Practices for Sampling Water from Closed ConduitsD3694 Practices for Pre

9、paration of Sample Containers andfor Preservation of Organic ConstituentsD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4448 Guide for Sampling Ground-Water Monitoring Wells3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTer

10、minology D1129.4. Summary of Practice4.1 This practice employs adsorbent/liquid or adsorbent/gasextraction to isolate compounds of interest.An aqueous sampleis added to a septum-sealed vial. The aqueous phase or itsheadspace is then exposed to an adsorbent coated on a fusedsilica fiber. The fiber is

11、 desorbed in the heated injection port ofa GC or GC-MS or the injector of an high-performance liquidchromatography (HPLC).4.2 The desorbed organic analytes may be analyzed usinginstrumental methods for specific volatile or semi-volatileorganic compounds. This practice does not include sampleextract

12、clean-up procedures.5. Significance and Use5.1 This practice provides a general procedure for the solidphase micro extraction of volatile and semi-volatile organiccompounds from an aqueous matrix or its headspace. Solidsorbent extraction is used as the initial step in the extraction oforganic consti

13、tuents for the purpose of quantifying or screeningfor extractable organic compounds.1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.06 on Methods for Analysis forOrganic Substances in Water.Current edition approved Dec. 15,

14、2018. Published January 2019. Originallyapproved in 2000. Last previous edition approved in 2012 as D6520 06 (2012).DOI: 10.1520/D6520-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume

15、information, refer to the standards 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 standard

16、ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.2 Typical detection limits that can be achieved usingSPME techniques with gas chromatograp

17、hy with flame ioniza-tion detector (FID), electron capture detector (ECD), or with amass spectrometer (MS) range from mg/L to g/L. Thedetection limit, linear concentration range, and sensitivity ofthe test method for a specific organic compound will dependupon the aqueous matrix, the fiber phase, th

18、e sampletemperature, sample volume, sample mixing, and the determi-native technique employed.5.3 SPME has the advantages of speed, no desorptionsolvent, simple extraction device, and the use of small amountsof sample.5.3.1 Extraction devices vary from a manual SPME fiberholder to automated commercia

19、l device specifically designedfor SPME.5.3.2 Listed below are examples of organic compounds thatcan be determined by this practice. This list includes both highand low boiling compounds.Volatile Organic Compounds (1-3)3Pesticides, General (4, 5)Organochlorine Pesticides (6)Organophosphorous Pesticid

20、es (7, 8)Polyaromatic Hydrocarbons (9, 10)Polychlorinated Biphenyls (10)Phenols (11)Nitrophenols (12)Amines (13)5.3.3 SPME may be used to screen water samples prior topurge and trap extraction to determine if dilution is necessary,thereby eliminating the possibility of trap overload.6. Principles of

21、 SPME6.1 SPME is an equilibrium technique where analytes arenot completely extracted from the matrix. With liquid samples,the recovery is dependent on the partitioning or equilibrium ofanalytes among the three phases present in the sampling vial:the aqueous sample and headspace (Phase 1), the fiber

22、coatingand aqueous sample (Phase 2), and the fiber coating and theheadspace (Phase 3):Phase 1! K15 CL/Cg(1)Phase 2! K25 CF/CL(2)Phase 3! K35 CF/CG(3)where CL, CG, and CFare the concentrations of the analytein these phases.6.1.1 Distribution of the analyte among the three phases canbe calculated usin

23、g the following:C0VL5 CGVG1CLVL1CFVF(4)6.1.2 Concentration of analyte in fiber can be calculatedusing the following:CF5 C0VLK1K2/VG1K1VL1K1K2VF(5)7. Interferences7.1 Reagents, glassware, septa, fiber coatings, and othersample processing hardware may yield discrete artifacts orelevated baselines that

24、 can cause poor precision and accuracy.7.1.1 Glassware should be washed with detergent, rinsedwith water, and finally rinsed with distilled-in-glass acetone.Air dry or in 103C oven. Additional cleaning steps may berequired when the analysis requires levels of g/L or below.Once the glassware has been

25、 cleaned, it should be usedimmediately or stored wrapped in aluminum foil (shiny sideout) or under a stretched sheet of PTFE-fluorocarbon.7.1.2 Plastics other than PTFE-fluorocarbon should beavoided. They are a significant source of interference and canadsorb some organics.7.1.3 A field blank prepar

26、ed from water and carried throughsampling, subsequent storage, and handling can serve as acheck on sources of interferences from the containers.7.2 When performing analyses for specific organiccompounds, matrix interferences may be caused by materialsand constituents that are coextracted from the sa

27、mple. Theextent of such matrix interferences will vary considerablydepending on the sample and the specific instrumental analysismethod used. Matrix interferences may be reduced by choosingan appropriate SPME adsorbing fiber.8. The Technique of SPME8.1 The technique of SPME uses a short, thin solid

28、rod offused silica (typically 1-cm long and 0.11-m outer diameter),coated with a film (30 to 100 M) of a polymer, copolymer,carbonaceous adsorbent, or a combination of these. The coated,fused silica (SMPE fiber) is attached to a metal rod and theentire assembly is a modified syringe (see Fig. 1).3Th

29、e boldface numbers in parentheses refer to a list of references at the end ofthis standard.NOTE 1This image originally appeared in Advances inChromatography, Fig. 5, Vol 37, 1997, p. 218. Used with permission.FIG. 1 SPME Fiber Holder AssemblyD6520 1828.2 In the standby position, withdraw the fiber i

30、nto aprotective sheath. Place an aqueous sample containing organicanalytes or a solid containing organic volatiles into a vial, andseal the vial with a septum cap.8.3 Push the sheath with fiber retracted through the vialseptum and lower into the body of the vial. Inject the fiber intothe headspace o

31、r the aqueous portion of the sample (see Fig. 2).Generally, when 2-mL vials are used, headspace samplingrequires approximately 0.8 mL of sample and direct samplingrequires 1.2 mL.8.4 Organic compounds are absorbed onto the fiber phasefor a predetermined time. This time can vary from less than 1min f

32、or volatile compounds with high diffusion rates such asvolatile organic solvents, to 30 min for compounds of lowvolatility such as polycyclic aromatic hydrocarbons (PAHs).8.5 Withdraw the fiber into the protective sheath and pullthe sheath out of the sampling vial.8.6 Immediately insert the sheath t

33、hrough the septum of thehot GC injector (see Fig. 3), push down the plunger, and insertthe fiber into the injector liner where the analytes are thermallydesorbed and subsequently separated on the GC column.8.6.1 The blunt 23-gage septum-piercing needle of theSPME is best used with a septumless injec

34、tor seal. These aremanufactured by several sources for specific GC injectors.8.6.2 A conventional GC septum may be used with SPME.A septum lasts for 100 runs or more. To minimize septumfailure, install a new septum, puncture with a SPME sheaththree or four times, and remove and inspect the new septu

35、m.Pull off and discard any loose particles of septum material, andreinstall the septum.8.6.3 The user should monitor the head pressure on thechromatographic column as the fiber sheath enters and leavesthe injector to verify the integrity of the seal. A subtle leak willbe indicated by unusual shifts

36、in retention time or the presenceof air in a mass spectrometer.8.7 Ensure that the injector liner used with SPME is notpacked or contains any physical obstructions that can interferewith the fiber. The inner diameter of the insert should optimallyshould be about 0.75 to 0.80 mm. Larger inserts (2 to

37、 4 mm)may result in broadening of early eluting peaks. SPME insertsare available commercially and may be used for split orsplitless injection. With splitless injection, the vent is timed toopen at the end of the desorption period (usually 2 to 10 min).8.8 Injector temperature should be isothermal an

38、d normally10 to 20C below the temperature limit of the fiber or the GCcolumn (usually 200 to 280C), or both. This provides rapiddesorption with little or no analyte carryover.9. Selection of Fiber Phase9.1 The selection of the fiber phase depends on severalfactors, including:9.1.1 The media being ex

39、tracted by the fiber, aqueous orheadspace;9.1.2 The volatility of the analyte such as gas phase hydro-carbons to semi-volatile pesticides; and9.1.3 The polarity of the analyte.9.2 A selection of fiber phases and common applications isshown in Table 1.10. Apparatus10.1 SPME Holder, manual sampling or

40、 automated sam-pling.10.2 SPME Fiber Assembly.10.3 SPME Injector Liner, that is, inserts for gas chromato-graphs.10.4 Septum Replacement Device.10.5 Vials, with septa and caps, for manual or automation.For automation, use either 2 or 10-mL vials.FIG. 2 Process for Adsorption of Analytes from Sample

41、Vial withSPME FiberFIG. 3 Injection Followed by Desorption of SPME Fiber in Injec-tion Port of ChromatographD6520 18311. Reagents11.1 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water that meetsthe purity specifications of Type I or Type II water,

42、 presentedin Specification D1193.11.2 Chemicals, standard materials, and surrogates shouldbe reagent or American Chemical Society (ACS) grade orbetter. When they are not available as reagent grade, theyshould have an assay of 90 % or better.11.3 Sodium Chloride (NaCl), reagent grade, granular.12. Ha

43、zards12.1 The toxicity and carcinogenicity of chemicals used inthis practice have not been precisely defined. Each chemicalshould be treated as a potential health hazard. Exposure tothese chemicals should be minimized. Each laboratory isresponsible for maintaining awareness of Occupational Safetyand

44、 Health Administration (OSHA) regulations regarding safehandling of chemicals used in this practice.12.2 If using either solvent, the hazard of peroxide forma-tion should be considered. Test for the presence of peroxideprior to use.13. Sample Handling13.1 There are many procedures for acquiring repr

45、esenta-tive samples of water. The choice of procedure is site andanalysis specific. There are severalASTM guides and practicesfor sampling.4Two good sources are Practices D3370 andGuide D4448.13.2 The recommended sample size is 40 to 100 mL. Moreor less sample can be used depending upon the sampleav

46、ailability, detection limits required, and the expected con-centration level of the analyte. Volatile organic analysis (VOA)vials of 40-mL capacity are commonly used as samplingcontainers. Any headspace should be eliminated if volatilesanalysis is required.13.3 Sample Storage:13.3.1 All samples must

47、 be iced or refrigerated to 4C fromthe time of collection until ready for extraction.13.3.2 Samples should be stored in a clean, dry place awayfrom samples containing high concentrations of organics.13.4 Sample Preservation:13.4.1 Some compounds are susceptible to rapid biologicaldegradation under c

48、ertain environmental conditions. If biologi-cal activity is expected, adjust the pH of the sample to about 2by adding hydrochloric acid (HCl). The constituent of concernmust be stable under acid conditions. For additionalinformation, see Practices D3694.13.4.2 If residual chlorine is present, add so

49、dium thiosulfateas a preservative (30 mg per 120-mL bottle).14. Optimizing SPME Sampling Parameters14.1 Liquid sampling and headspace sampling give approxi-mately the same recovery for volatiles but not for semi-volatiles. Semi-volatiles are best extracted with SPME liquidsampling. Headspace sampling is desirable if samples containnonvolatile compounds such as salts, humic acids, or proteins.14.2 Sample mixing is effective in increasing the responseof semi-volatile analytes. It reduces the equilibrium time forthe adsorption of the semi-volatile components. Mixing re-d