1、Designation: D 6889 03Standard Practice forFast Screening for Volatile Organic Compounds in WaterUsing Solid Phase Microextraction (SPME)1This standard is issued under the fixed designation D 6889; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of 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 practice covers a procedure for the screening oftrace levels of volatile organic comp
3、ounds in water samples byheadspace solid phase microextraction (SPME) in combinationwith fast gas chromatography with flame ionization detection.1.2 The results from this screening procedure are used toestimate analyte concentrations to prevent contamination ofpurge and trap or headspace analytical
4、systems.1.3 The compounds of interest must have a greater affinityfor the SPME absorbent polymer or adsorbent than the samplematrix or headspace phase in which they reside.1.4 Not all of the analytes which can be determined bySPME are addressed in this practice. The applicability of theabsorbent pol
5、ymer, adsorbent or combination to extract thecompound(s) of interest must be demonstrated before use.1.5 Where used it is the responsibility of the user to validatethe application of SPME to the analytes of interest.1.6 The values stated in SI units are to be regarded as thestandard.1.7 This standar
6、d 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 limitations prior to use. For specific hazardstatements,
7、 see Section 9.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 3694 Practices for Preparation of Sample Containers andfor Preservation of Organic ConstituentsD 3856 Practice for Evaluating Laboratories Engaged inSampling and Anal
8、ysis of Water and WastewaterD 4210 Practice for Intralaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level DataD 6520 Practice for the Solid Phase Micro Extraction(SPME) of Water and its Headspace for the Analysis ofVolatile and Semi-Volatile Organic Compounds3. Summary of P
9、ractice3.1 This practice employs adsorbent/gas extraction to iso-late compounds of interest, see Practice D 6520. An aqueoussample is added to a small (2 mL) septum sealed vial. Salt isused to improve analyte recovery. After the addition of asurrogate standard and a short mixing cycle, a SPME fuseds
10、ilica fiber coated with a thick polymer film is then exposed tothe aqueous headspace for a few seconds. The fiber is thendesorbed in the heated injection port of a GC/FID or GC-MSand the resulting analytes chromatographed on a short narrowbore capillary column. The total analysis time is approximate
11、ly3 min.3.2 The concentrations of the volatile organics in the watersample are estimated to determine whether the sample may beanalyzed directly or first diluted prior to purge and trap orheadspace analysis.4. Significance and Use4.1 This practice provides a general procedure for thesolid-phase micr
12、oextraction (SPME) of volatile organic com-pounds from the headspace of an aqueous matrix. Absorbentextraction is used as the initial step in the extraction of organicconstituents for the purpose of screening and subsequentlyestimating the concentration of the volatile organic compo-nents found in w
13、ater samples. This information may then beused to determine whether a sample may be analyzed directlyby purge and trap or headspace or will require dilution prior toanalysis.4.2 Typical detection limits that can be achieved usingSPME techniques with gas chromatography (GC) with a flameionization det
14、ector (FlD) range from milligrams per litre(mg/L) to micrograms per litre (g/L). The detection limit,linear concentration range, and sensitivity of this test method1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.06 on Method
15、s for Analysis forOrganic Substances in Water.Current edition approved March 10, 2003. Published April 2003.2For 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 stan
16、dards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.for a specific organic compound will depend upon the aqueousmatrix, the fiber phase, the sample temperature, sample vol-ume, sample mixing
17、, and the determinative technique em-ployed.4.3 Solid phase microextraction has the advantage of speed,reproducibility, simplicity, no solvent, small sample size, andautomation.4.3.1 Extraction devices vary from a manual SPME fiberholder to automated commercial devices specifically designedfor SPME.
18、4.3.2 Apartial list of volatile organic compounds that can bescreened by this practice is shown in Table 1.5. Principles of SPME5.1 Solid phase microextraction is an equilibrium techniquewhere analytes are not completely extracted from the matrix.With liquid samples, the recovery is dependent on the
19、 parti-tioning or equilibrium of analytes among the three phasespresent in the sampling vial: the aqueous sample and headspace(Eq 1), the fiber coating and aqueous sample (Eq 2), and thefiber coating and the headspace (Eq 3):K15 CL/Cg(1)K25 CF/CL(2)K35 CF/CG(3)where:CL,CG, and CF= concentrations of
20、the analyte in thesephases.5.1.1 Distribution of the analyte among the three phases:C0VL5 CGVG1 CLVL1 CFVF(4)5.1.2 Concentration of analyte in fiber:CF5 C0VLK1K2/VG1 K1VL1 K1K2VF(5)6. Interferences6.1 Reagents, glassware, septa, fiber coatings and othersample processing hardware may yield discrete a
21、rtifacts orelevated baselines that can cause poor precision and accuracy.See Terminology D 1129.6.1.1 Plastics other than PTFE-fluorocarbon should beavoided. They are a significant source of interference and canadsorb some organics.7. Apparatus7.1 SPME Holder, manual or automated sampling.7.1.1 SPME
22、 Fiber AssemblyPolydimethylsiloxane(PDMS), 30uM or equivalent fiber suitable for volatiles ad-sorption.7.2 Vials with Septa and Caps, for manual or automatedSPME. Vials for automation, 2 mL.7.3 Gas Chromatograph, with flame ionization detector.7.3.1 GC Column, 10 m by 0.25 mm, 1uM film MethylSilicon
23、e, or equivalent.7.3.2 GC Guard Column, 1m by 0.32 mm uncoated, orequivalent.7.3.3 Split/splitless Injector, with 0.75 to 1.0 mm insidediameter insert.7.3.4 Optional Septum Replacement Device.7.3.5 Optional SPME Autosampler.7.3.6 GC Compatible Workstation.8. Reagents8.1 Purity of WaterUnless otherwi
24、se indicated, referenceto water shall be understood to mean reagent water conformingto Type II of Specification D 1193.8.2 Chemicals, standard materials and surrogates should bereagent or ACS grade or better. When they are not available asreagent grade, they should have an assay of 90 % or better.8.
25、3 Sodium Chloride (NaCl), reagent grade, granular.8.4 Surrogate Standard, 30 mg/L, 1,4-dichlorobenzene-d4in methanol.8.5 Check StandardPrepare a check standard in methanol.Check standard should contain 30 mg/L 1,4-dichlorobenzene-d4plus VOCs that will be screened. A typicalcheck standard will provid
26、e aqueous concentrations shown inTable 1 when spiking 4 L of check standard to 700 L watersample.9. Hazards9.1 The toxicity and carcinogenicity of chemicals used orthat could be used in this practice have not been preciselydefined. Each chemical should be treated as a potential healthhazard. Exposur
27、e to these chemicals should be minimized.Each laboratory is responsible for maintaining awareness ofOSHA regulations regarding safe handling of chemicals usedin this practice.10. Sample Handling10.1 There are many procedures for acquiring representa-tive samples of water. The procedure chosen will b
28、e site andanalysis specific. There are several guides and practices forsampling listed in the ASTM subject index under Sampling,Water Applications.10.2 The recommended sample size is 40 to 100 mL. Moreor less sample can be used depending upon the sampleTABLE 1 Check Standard Composition for Screenin
29、g VOCsin WaterAnalyteSample Composition,g/LDetection Limit,g/LTBA 100 000 10 000Methyl-t-butyl ether 1000 150cis-1,2-Dichloroethene 3000 3001,1,1-Trichloroethane 1000 200Benzene 400 401,1,1-Trichloroethane 700 120Toluene 200 10Tetrachloroethene 300 50Chlorobenzene 150 10Ethylbenzene 100 5m-Xylene 10
30、0 5styrene 100 5o-Xylene 100 5Isopropylbenzene 100 52-Chlorotoluene 100 51,2,4-Trimethylbenzene 100 51,4-Dichlorobenzene-d4 150 51,2-Dichlorobenzene 100 5Napthalene 100 5D6889032availability, detection limits required, and the expected con-centration level of the analyte. Forty-milliliter VOA vials
31、arecommonly used as sampling containers. Any headspace shouldbe eliminated since volatiles analysis is required.10.3 Sample Storage:10.3.1 All samples must be iced or refrigerated to 4C fromthe time of collection until ready for extraction.10.3.2 Samples should be stored in a clean dry place awayfro
32、m samples containing high concentrations of organics.10.4 Sample Preservation:10.4.1 Some compounds are susceptible to rapid biologicaldegradation under certain environmental conditions. If biologi-cal activity is expected, adjust the pH of the sample to about 2by adding HCI. The constituents of con
33、cern must be stableunder acid conditions. For additional information, see PracticeD 3694.10.4.2 If residual chlorine is present, add sodium thiosulfateas a preservative (30 mg/4 oz bottle).11. Quality Control11.1 Minimum quality control requirements include aninitial demonstration of laboratory capa
34、bility, analysis ofmethod blanks and quality control check samples. For ageneral discussion of good laboratory practices, see GuideD 3856 and Practice D 4210.11.2 Precision is initially determined by running at least fivequality control check standards prepared by spiking reagentgrade water with a m
35、ethanol solution of target analytes.Subsequently, batch precision is determined by splitting spikedquality control check standards into two equal portions.11.3 Method blanks are prepared using distilled or deion-ized water. The blanks must be carried through the entireanalytical procedure with the s
36、amples. Each time a group ofsamples are run, several method blanks should be run.11.4 A surrogate standard is added to each vial prior toSPME extraction.11.5 Several quality control check standards should be runwith each batch of samples to average one for every twentysamples. The QC check samples s
37、hould demonstrate recoveriesof 630 %. Recalibration is necessary if this is not achieved.11.6 One calibration standard at the highest concentration isrequired for each analyte to cover the concentration rangebeing screened.FIG. 1 Fiber HolderFIG. 2 Process for Adsorption of Analytes from Sample Vial
38、 withSPME FiberFIG. 3 Injection Followed by Desorption of SPME Fiber inInjection Port of ChromatographD688903311.7 All calibration and quality control check standardsmust be extracted using the same procedures, and conditions asthe samples.12. Procedure12.1 Ahead of time prepare 2 mL septum-capped v
39、ials with0.35 g NaCl.12.2 Remove water samples from storage and allow them toequilibrate to room temperature.12.3 Spike each vial with 4 L surrogate standard solution(1,4-dichlorobenzene-d4).12.4 Remove the container cap from the sample container.Make a volumetric transfer of 0.7 mL of this sample t
40、o the 2mL volume septum-capped vial.12.5 Vortex each sample for approximately 5 to 10 s.12.6 Insert SPME shaft through septum into headspaceabove sample.12.7 Depress plunger either manually or automatically andexpose fiber coating to headspace.12.8 An extraction time of approximately 12 s is adequat
41、e.No mixing is required.12.9 Following extraction, retract fiber into protectivesheath and remove from vial.12.10 Inject sheath through GC septum and in splitlessmode depress plunger into a 250C heated injector insertdesorbing analytes to column. Desorption time is about 0.2min.12.11 Analyze desorbe
42、d analytes by GC/FID with the fol-lowing parameters:Injector, 250CGC Column Oven: 70C for 0.2 min, 50/min to 180Carrier Gas: Hydrogen, 12 psi head pressureDetector: 250C13. Calibration, Standardization and Analysis13.1 While the recovery of analytes with a SPME fiber isrelatively low, the degree of
43、extraction is consistent so thatSPME is quantitative with linearity, precision and accuracy.Examples of upper and lower quantitation levels obtained withthis screening technique are shown in Table 1.13.2 For simple or clean sample matrices such as drinkingwater, external standard calibration is used
44、.13.3 Prepare calibration standards by spiking reagent waterwith a portion of the stock standard solution. Prepare a blankand a single calibration standard to cover the appropriate range.Analyze the solutions and record the readings. Repeat theoperation a sufficient number of times to obtain a relia
45、bleaverage reading for each solution.13.4 Construct a single point plus origin analytical curve byplotting the concentration of the standard versus its response asprovided by the instrument workstation. Analyze the unknownusing the same procedure and determine the approximateanalyte concentration.14
46、. Precision and Bias14.1 Precision and bias cannot be determined directly forthis screening procedure. Precision and bias should be gener-ated in the laboratory on the parameters of concern. Examplesof this type of data may be found in the literature for volatileorganic compounds; see References.15.
47、 Keywords15.1 screening; solid phase microextraction; SPME; vola-tile; waterREFERENCES(1) Schumacher, T. L., “Fast Prescreening of Water and Soil SamplesUsing Solid-Phase Microextraction,” Eastern Analytical Symposium,Somerset, NJ, November, 1996.(2) Nilsson, T., Pelusio, F., Montanarelle, L., Larse
48、n, B., Facchetti, S., andMadsen, J., “An Evaluation of Solid-Phase Microextraction forAnaly-sis of Volatile Organic Compounds in Drinking Water,” J. High Resol.Chromatogr., Vol 18, 1995, pp. 617-624.(3) Chai, M., Arthur, C. L., Pawliszyn, J., Belardi, R. P., and Pratt, K. F.,“Determination of Volati
49、le Chlorinated Hydrocarbons inAir and Waterwith Solid-Phase Microextraction,” Analyst, Vol 118, No. 12, 1993, pp.1501-1505.(4) Penton, Z., “Determination of Volatile Organics in Water by GC withSolid-Phase Microextraction,” Proc. Water Qual. Technol. Conf. 1994,pp. 1027-1033.(5) Gorecki, T., Mindrup, R., and Pawliszyn, J., “Pesticides by Solid-Phase Microextraction. Results of a Round Robin Test,” Analyst,Vol121, 1996, pp. 1381-1386.(6) Boyd-Boland, A. A., Magdic, S., and Paawliszyn, J., “SimultaneousDetermination of 60 Pesticides in Water by Solid-Phase Microextrac-ti
