1、Designation: E2881 13Standard Test Method forExtraction and Derivatization of Vegetable Oils and Fatsfrom Fire Debris and Liquid Samples with Analysis by GasChromatography-Mass Spectrometry1This standard is issued under the fixed designation E2881; the number immediately following the designation in
2、dicates the year oforiginal 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 test method covers the extraction,
3、derivatization,and identification of fatty acids indicative of vegetable oils andfats in fire debris and liquid samples. This procedure will alsoextract animal oils and fats, as these are similar in chemicalcomposition to vegetable oils and fats. Herein, the phrase “oilsand fats” will be used to ref
4、er to both animal and vegetablederived oils and fats.1.2 This test method is suitable for successfully extractingoil and fat residues having 8 to 24 carbon atoms.1.3 The identification of a specific type of oil (for example,olive, corn, linseed) requires a quantitative analysis of the fattyacid este
5、rs and is beyond the scope of this test method.1.4 This test method cannot replace the requisiteknowledge, skills, or abilities acquired through appropriateeducation, training, and experience and should be used inconjunction with sound professional judgment.1.5 The values stated in SI units are to b
6、e 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 this standard to establish appro-priate safety and health practices and d
7、etermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E620 Practice for Reporting Opinions of Scientific or Tech-nical ExpertsE1386 Practice for Separation of Ignitable Liquid Residuesfrom Fire Debris Samples by Solvent ExtractionE1388 Practice
8、for Sampling of Headspace Vapors from FireDebris SamplesE1412 Practice for Separation of Ignitable Liquid Residuesfrom Fire Debris Samples by Passive Headspace Concen-tration With Activated CharcoalE1413 Practice for Separation of Ignitable Liquid Residuesfrom Fire Debris Samples by Dynamic Headspac
9、e Con-centrationE1492 Practice for Receiving, Documenting, Storing, andRetrieving Evidence in a Forensic Science LaboratoryE1618 Test Method for Ignitable Liquid Residues in Extractsfrom Fire Debris Samples by Gas Chromatography-MassSpectrometryE2154 Practice for Separation and Concentration of Igni
10、t-able Liquid Residues from Fire Debris Samples by Pas-sive Headspace Concentration with Solid Phase Microex-traction (SPME)E2451 Practice for Preserving Ignitable Liquids and Ignit-able Liquid Residue Extracts from Fire Debris Samples3. Summary of Test Method3.1 If ignitable liquid analysis is requ
11、ired, it shall beperformed prior to analysis for oils and fats as this test methodis a destructive technique. A fire debris sample (or sub-sample)or an aliquot of a liquid is initially analyzed for ignitable liquidresidues using standards listed in referenced documents.3.2 The same sample of fire de
12、bris (or different sub-sample)or an additional aliquot of a liquid is then extracted with anorganic solvent, and a derivatizing agent is added to converteither the free fatty acids and some triglycerides (for acid-catalyzed derivatization) or just the triglycerides (for base-catalyzed derivatization
13、) to fatty acid methyl esters (FAMEs).3.3 The organic layer of solvent is removed, filtered, andconcentrated if necessary, using dry nitrogen, filtered air, orinert gas.3.4 The derivatized extract is analyzed by gaschromatography-mass spectrometry (GC-MS).1This test method is under the jurisdiction
14、ofASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition approved June 1, 2013. Published October 2013. DOI: 10.1520/E2881-13.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
15、United States13.5 Specific chemical components (fatty acid methyl esters)are identified by their retention times and mass spectra.4. Significance and Use4.1 This test method is useful when oils and fats aresuspected as an ignition source or a fuel source in a fire.4.1.1 The identification of oil and
16、 fat residues in samplesfrom a fire scene can support the field investigators opinionregarding the origin and cause of the fire.4.1.2 The positive identification of fatty acid(s) does notnecessarily mean that the fire was caused by self heating.4.2 This test method specifically identifies fatty acid
17、 deriva-tives. Oils and fats are comprised primarily of triglycerides(which are fatty acids attached to a glycerol backbone), andsome free fatty acids. Free fatty acids and triglycerides are noteasily analyzed by the traditional ignitable liquid extractiontechniques. Solvent extraction and derivatiz
18、ation to FAME willenable identification by GC-MS.4.2.1 The identification of an individual fatty acid in firedebris samples does not confirm the presence of oils or fats;however, there are times when large quantities of the oil or fatmay be extracted. In such cases a more positive identificationcan
19、be made.4.2.2 Oils and fats containing fatty acids with no doublebonds will generally have no tendency to self-heat. Withincreasing unsaturation (1, 2 and 3 double bonds), the tendencyto self-heat also increases, such that polyunsaturated fatty acids(PUFAs), such as C18:3, have a high tendency to se
20、lf-heat.4.3 This test method is a sensitive separation technique andcan detect quantities as small as 3 L of oil or fat residue in anextract from a debris sample.4.4 This test method shall be performed after all requiredtraditional testing for ignitable liquid residues is completed.4.5 This test met
21、hod extracts liquids and residues fromporous and nonporous materials of various sizes.4.6 This test method can be hampered by coincident extrac-tion of interfering compounds present in the fire debrissamples.4.7 This is a destructive technique and whenever possiblethe entire sample should not be use
22、d for the procedure. It isrecommended that visual inspection be used to locate portionsor areas exhibiting potential oily residue for sub-samplingwhich would preserve remaining portions for further analysesand also minimize solvent waste. The solvent extracted por-tions of the sample are not suitabl
23、e for resampling.4.8 Alternate methods of extraction, derivatization, oranalysis exist and may be suitable for use in obtaining similarresults and conclusions.4.9 Biodiesel, an ignitable liquid, is a trans-esterified prod-uct containing FAMEs. The FAME compounds in biodiesel canbe detected in fire d
24、ebris using many fire debris extractiontechniques followed directly by GC-MS analysis. Derivatiza-tion is not necessary to identify the FAMEs in biodiesel5. Apparatus5.1 Gas ChromatographA chromatograph capable of us-ing capillary columns and being interfaced to a mass spectrom-eter.5.1.1 Sample Inl
25、et SystemA sample inlet system that canbe operated in either split or splitless mode with capillarycolumns; the inlet system may use on-column technology.5.1.2 ColumnAcapillary, bonded phase, methylsilicone orphenylmethylsilicone column or equivalent, or a polarcapillary, bonded phase, such as a cya
26、nopropyl-based fatty acidspecific column, may be used to determine the presence of fattyacids.5.1.2.1 A polar capillary, bonded phase, such as acyanopropyl-based fatty acid specific column shall be used toperform comparative analysis between neat liquid samples, orfire debris samples, or both. Any c
27、olumn length or temperatureprogram conditions may be used provided that each componentof the reference mixture (see 6.8) is adequately separated onthe polar column.5.1.3 GC OvenA column oven capable of reproducibletemperature program operation in the range from 50 to 300C.5.2 Mass SpectrometerCapabl
28、e of acquiring mass spectrafrom m/z 40 to m/z 400 with unit resolution or better, withcontinuous data output.5.2.1 Sensitivity and ResolutionThe system shall be ca-pable of detecting each component of the reference mixture(see 6.8) and providing sufficient ion intensity data to identifyeach componen
29、t, either by computer library search or bycomparison with reference spectra.5.3 Data StationA computerized data station capable ofstoring time sequenced mass spectral data from sample runs.5.3.1 Data HandlingThe data system shall be capable ofperforming, either through its operating system or by use
30、rprogramming, various data handling functions, including inputand storage of sample data files, generation of extracted ionprofiles, searching data files for selected compounds, andqualitative and semi-quantitative compound analysis.5.3.2 Mass Spectral LibrariesThe system shall be capableof retrievi
31、ng a specified mass spectrum from a data file andcomparing it against a library of mass spectra available to thedata system. This capability is considered an aid to the analyst,who will use it in conjunction with chromatographic data andknown reference materials to identify unknown components.5.4 Sy
32、ringesA syringe capable of introducing a samplesize in the range from 0.1 to 10.0 m.5.5 Steam bath, for use in warming sample extracts incontainers used during evaporation steps.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. It is intended that all
33、reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society. Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.E2881 1326.2 So
34、lventA suitable solvent, such as n-pentane,n-hexane, or n-heptane.6.2.1 Solvent purity can be verified by evaporating to atleast twice the extent used in the analysis and analyzing theevaporated solvent in accordance with Test Method E1618.6.3 Derivatization ReagentThere are two types of deriva-tiza
35、tion processes: (1) acid-catalyzed, which will act on bothtriglycerides and free fatty acids; and (2) base-catalyzed, whichonly trans-esterify triglycerides. A suitable derivatizationreagent, such as a 2N potassium hydroxide (KOH) in methanolsolution (base-catalyzed) or a 10 % boron trifluoride inme
36、thanol solution (acid-catalyzed), will be chosen to convertthe fatty acids and triglycerides to FAMEs.6.4 Drying AgentA suitable drying agent, such as anhy-drous sodium sulfate.6.5 Filter apparatus, free of extractable hydrocarbons, oils,and fats.6.6 Evaporation AccelerantsCompressed dry nitrogen,fi
37、ltered air, or inert gas used in the concentration of solventextracts.6.7 Carrier GasHelium or hydrogen of purity 99.995 %or higher.6.8 Reference MixtureThe reference mixture shall consistof a minimum of the following FAMEs: C16:0, C18:0, C18:1,C18:2, C18:3. Additional compounds may be included at t
38、hediscretion of the analyst. The mixture should contain approxi-mately equal parts by weight of the required fatty acids methylesters in the chosen solvent or a traceable commerciallyavailable reference mixture. The final solution is prepared bydiluting the above mixture such that the concentration
39、of eachcomponent is no greater than 0.005 % weight/volume (0.05micrograms/milliliter) in the chosen solvent. A typical chro-matogram including components of the reference mixture on atypical non-polar fire debris column is shown in Fig. 1.AInstrument: HP 6890 Gas ChromatographDetector: HP 5972 Mass
40、Selective DetectorColumn: 30m0.25mm0.25m,DB-1MS(polydimethylsiloxane)Mobile Phase: Helium, 0.5 mL/minSample: 1 LInjector: 250CInitial Temperature: 60C for 3 minRate: 5C/min to 120C for 0 min12C/min to 300C for 5 minTotal Run Time: 35 minSplit: 20:1FIG. 1 Total Ion Chromatogram (TIC) of a FAME Refere
41、nce Mixture on a DB-1MS Capillary Column Using Test Method E1618 GC-MSConditionsE2881 133typical chromatogram including components of the referencemixture on a fatty acid specific column is shown in Fig. 2.6.9 Reference Oils and FatsOils and fats should beavailable for comparison and identification
42、purposes.6.9.1 Typically, FAMEs derived from reference oils and fatsare diluted approximately 1:200 in an appropriate solvent andderivatized using the same procedure that will be used on thedebris and liquid samples. Depending on the column capacityand injection technique, derivatized oil and fat so
43、lutions can beconcentrated to ensure detection of minor compounds.6.10 Glassware or LabwareClean glassware (beakers, testtubes, and vials) or disposable labware free of extractablehydrocarbons, oils, and waxes.7. Equipment Calibration and Maintenance7.1 Verify the consistent performance of the chrom
44、ato-graphic instrument by using blanks and a known concentrationof the reference mixture (see 6.8). Optimize gas flow periodi-cally.7.2 Tune and Calibrate Mass Spectrometer:7.2.1 Ensure proper operation of the mass spectrometerusing perfluorotributylamine (PFTBA), or another appropriatecalibration s
45、tandard, according to the instrument manufactur-ers specifications, prior to use. This should be done at leastevery day that the instrument is used or in accordance withmanufacturers recommendations.7.2.2 Maintain tuning documentation as a portion of thequality control documentation.7.3 Equipment Ma
46、intenance:7.3.1 Change septa and clean or replace injector liners on aperiodic basis to avoid sample contamination by carryover ofresidual material from previous sample injections.8. Sample Handling Procedure8.1 Only samples of appropriate dilution should be analyzedon a GC-MS system8.2 Care must be
47、 taken to ensure that samples and extractscontaining a small quantity of triglycerides and free fatty acidsInstrument: HP 6890 Gas ChromatographDetector: HP 5973 Mass Selective DetectorColumn: 30m0.25mm0.25m,SupelcoASP-2380 poly (90 % biscyanopropyl/10 %cyanopropylphenyl siloxane)Mobile Phase: Heliu
48、m, 1.0 mL/minSample: 1 LInjector: 250CInitial Temperature: 105C for 0 minRate: 4C/min to 200C for 0 min20C/min to 260C for 0 minTotal Run Time: 26.75 minSplit: 20:1AA trademark by Sigma-Aldrich Co., LLC.FIG. 2 Total Ion Chromatogram (TIC) of a FAME Reference Mixture on a SP-2380 Capillary Column Usi
49、ng a Program Optimized for Oiland Fat AnalysisE2881 134are not subjected to heat or evaporated to dryness prior toderivatization, as both of these may change the composition ofthe extract.8.3 Analyze solvent blanks at least once each day that theinstrument is used; maintain these analysis records. This willverify the purity of the solvent and potentially detect carryoveror contamination.8.4 Clean syringes thoroughly between injections to ensureno carryover.8.4.1 Conduct carryover studies, and maintain records thatdemonstrate the adequacy o
