ASTM D6889-03(2017) Standard Practice for Fast Screening for Volatile Organic Compounds in Water Using Solid Phase Microextraction (SPME).pdf

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1、Designation: D6889 03 (Reapproved 2017)Standard Practice forFast Screening for Volatile Organic Compounds in WaterUsing Solid Phase Microextraction (SPME)1This standard is issued under the fixed designation D6889; the number immediately following the designation indicates the year oforiginal adoptio

2、n 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 a procedure for the screening oftrace levels of volati

3、le organic compounds 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 headsp

4、ace analytical 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 t

5、heabsorbent polymer, 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 asstandard. No o

6、ther units of measurement 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 t

7、he applicability of regulatory limitations prior to use.For specific hazard statements, see Section 9.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Internatio

8、nal Standards, Guides 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 WaterD3694 Practices for Preparation of Sample Containers andfor

9、Preservation of Organic ConstituentsD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4210 Practice for Intralaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level Data(Withdrawn 2002)3D6520 Practice for the Solid Phase Micro Extraction(SPME) of W

10、ater and its Headspace for the Analysis ofVolatile and Semi-Volatile Organic Compounds3. Summary of Practice3.1 This practice employs adsorbent/gas extraction to iso-late compounds of interest, see Practice D6520. An aqueoussample is added to a small (2-mL) septum-sealed vial. Salt isused to improve

11、 analyte recovery. After the addition of asurrogate standard and a short mixing cycle, a SPME fusedsilica 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 gas chromatography/flame ionization

12、detector (GC/FID) or gas chromatography/mass spectrometry (GC-MS) and the resulting analytes chro-matographed on a short narrow bore capillary column. Thetotal analysis time is approximately 3 min.3.2 The concentrations of the volatile organics in the watersample are estimated to determine whether t

13、he 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 theSPME of volatile organic compounds from the headspace of an1This practice is under the jurisdiction of ASTM Committee D19 on Wa

14、ter andis the direct responsibility of Subcommittee D19.06 on Methods for Analysis forOrganic Substances in Water.Current edition approved Dec. 15, 2017. Published December 2017. Originallyapproved in 2003. Last previous edition approved in 2011 as D6889 03 (2011).DOI: 10.1520/D6889-03R17.2For refer

15、enced 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 standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced on

16、www.astm.org.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 Decision on Principles for theDevelop

17、ment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1aqueous matrix. Absorbent extraction is used as the initial stepin the extraction of organic constituents for the purpose ofscreening and subsequently estim

18、ating the concentration of thevolatile organic components found in water samples. Thisinformation may then be used to determine whether a samplemay be analyzed directly by purge and trap or headspace orwill require dilution prior to analysis.4.2 Typical detection limits that can be achieved usingSPM

19、E techniques with GC with a FID range from milligramsper litre (mg/L) to micrograms per litre (g/L). The detectionlimit, linear concentration range, and sensitivity of this testmethod for a specific organic compound will depend upon theaqueous matrix, the fiber phase, the sample temperature,sample v

20、olume, sample mixing, and the determinative tech-nique employed.4.3 SPME has the advantage of speed, reproducibility,simplicity, no solvent, small sample size, and automation.4.3.1 Extraction devices vary from a manual SPME fiberholder to automated commercial devices specifically designedfor SPME.4.

21、3.2 Apartial list of volatile organic compounds that can bescreened by this practice is shown in Table 1.5. Principles of SPME5.1 SPME is an equilibrium technique where analytes arenot completely extracted from the matrix. With liquid samples,the recovery is dependent on the partitioning or equilibr

22、ium ofanalytes among the three phases present in the sampling vial:the aqueous sample and headspace (Eq 1), the fiber coating andaqueous sample (Eq 2), and the fiber 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 the analyte in thesephases.

23、5.1.1 Distribution of the analyte among the three phases:C0VL5 CGVG1CLVL1CFVF(4)5.1.2 Concentration of analyte in fiber:CF5 C0VLK1K2/VG1K1VL1K1K2VF(5)6. Interferences6.1 Reagents, glassware, septa, fiber coatings, and othersample processing hardware may yield discrete artifacts orelevated baselines

24、that can cause poor precision and accuracy.See Terminology D1129.6.1.1 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 Fiber AssemblyPolydimethylsilo

25、xane(PDMS), 30 uM or equivalent fiber suitable for volatilesadsorption.7.2 Vials with Septa and Caps, for manual or automatedSPME. Vials for automation, 2 mL.7.3 Gas Chromatograph (GC), with flame ionization detec-tor.7.3.1 GC Column, 10 m by 0.25 mm, 1 uM film methylsilicone, or equivalent.7.3.2 GC

26、 Guard Column, 1 m 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 otherwise indicated, referencet

27、o water shall be understood to mean reagent water conformingto Type II of Specification D1193.8.2 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.8.3 Sodium Chloride (NaCl)

28、, 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 volatile organic compounds that willbe screened. A typical check standard will provide

29、aqueousconcentrations shown in Table 1 when spiking 4 L of checkstandard to 700-L water sample.TABLE 1 Check Standard Composition for Screening VolatileOrganic Compounds in WaterAnalyteSampleComposition,g/LDetection Limit,g/LTBA 100 000 10 000Methyl-t-butyl ether 1000 150cis-1,2-Dichloroethene 3000

30、3001,1,1-Trichloroethane 1000 200Benzene 400 401,1,1-Trichloroethane 700 120Toluene 200 10Tetrachloroethene 300 50Chlorobenzene 150 10Ethylbenzene 100 5m-Xylene 100 5styrene 100 5o-Xylene 100 5Isopropylbenzene 100 52-Chlorotoluene 100 51,2,4-Trimethylbenzene 100 51,4-Dichlorobenzene-d4 150 51,2-Dich

31、lorobenzene 100 5Napthalene 100 5D6889 03 (2017)29. 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. Exposure to these chemicals should be minimized.Each la

32、boratory 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 be site andanalysis specific. There are several g

33、uides 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 sampleavailability, detection limits required, and the expected con-centration level of the analyte.

34、Forty-millilitre VOA vials 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 i

35、n a clean dry place awayfrom 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 H

36、Cl. The constituents of concern must be stableunder acid conditions. For additional information, see PracticesD3694.10.4.2 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 demon

37、stration of laboratory capability, analysis ofmethod blanks, and quality control check samples. For ageneral discussion of good laboratory practices, see GuideD3856 and Practice D4210.11.2 Precision is initially determined by running at least fivequality control check standards prepared by spiking r

38、eagentgrade water with a methanol solution of target analytes.FIG. 1 Fiber HolderFIG. 2 Process for Adsorption of Analytes from Sample Vial withSPME FiberFIG. 3 Injection Followed by Desorption of SPME Fiber in Injec-tion Port of ChromatographD6889 03 (2017)3Subsequently, batch precision is determin

39、ed 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 samples. Each time a group ofsamples are run, several method blanks should be

40、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 quality control (QC) check samples shoulddemonstrate recoveries of 630 %. Recalibration is nece

41、ssary ifthis is not achieved.11.6 One calibration standard at the highest concentration isrequired for each analyte to cover the concentration rangebeing screened.11.7 All calibration and quality control check standardsmust be extracted using the same procedures, and conditions asthe samples.12. Pro

42、cedure12.1 Ahead of time prepare 2-mL septum-capped vials 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.

43、Make a volumetric transfer of 0.7 mL of this sample to the2-mL 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.

44、8 An extraction time of approximately 12 s is adequate.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.

45、Desorption time is about 0.2min.12.11 Analyze desorbed 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 analy

46、tes with a SPME fiber isrelatively low, the degree of 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

47、as drinkingwater, external standard calibration is used.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 theo

48、peration a sufficient number of times to obtain a reliableaverage 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 procedur

49、e and determine the approximateanalyte concentration.14. 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 the References section.15. Keywords15.1 screening; solid phase microextraction; SPME; vola-tile; waterD6889 03 (2017)4REFERENCES(1) Schumacher, T. L., “Fast Prescreening of Water and Soil SamplesUsing Solid-