1、Designation: E1413 13Standard Practice forSeparation of Ignitable Liquid Residues from Fire DebrisSamples by Dynamic Headspace Concentration1This standard is issued under the fixed designation E1413; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase 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 describes the procedure for separation ofsmall quantities of ignitable liqu
3、id residues from fire debrissamples using the method of dynamic headspace concentra-tion.1.2 Dynamic headspace concentration uses adsorption andsubsequent solvent elution or thermal desorption.1.3 Both positive and negative pressure systems for adsorp-tion are described, as well as a thermal desorpt
4、ion system.1.4 While this practice is suitable for successfully extractingignitable liquid residues over the entire range of concentration,the headspace concentration methods are best used when a highlevel of sensitivity is required due to a very low concentrationof ignitable liquid residues in the
5、sample.1.5 Alternate separation and concentration procedures arelisted in Section 2. If archival of the extract is of importance,then this practices thermal desorption procedure, SPME (Prac-tice E2154), and headspace (Practice E1388) sample separationtechniques are not recommended unless a portion o
6、f the extractcan be split and retained. In order to have an archivable extract,then this practices sample collection on charcoal, solventextraction (Practice E1386), or passive headspace concentra-tion (Practice E1412) is recommended.1.6 This practice offers a set of instructions for performingone o
7、r more specific operations. This standard cannot replaceknowledge, skill, or ability acquired through appropriateeducation, training, and experience and should be used inconjunction with sound professional judgment.1.7 This standard does not purport to address all of thesafety concerns, if any, asso
8、ciated 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.2. Referenced Documents2.1 ASTM Standards:2E1386 Practice for Separation of Ignitable Liquid Residue
9、sfrom Fire Debris Samples by Solvent ExtractionE1388 Practice 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 CharcoalE1459 Guide for Physical Evidence Labeli
10、ng and RelatedDocumentationE1492 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 Concentrat
11、ion of Ignit-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 Practice3.1 The sample, preferably in it
12、s original container, isheated, forcing volatile compounds to vaporize. The headspacein the sample is then drawn or pushed through a tubecontaining an adsorption media (typically activated charcoal orTenax) which adsorbs the vaporized compounds.3.2 Other solid adsorbents and collection systems can b
13、eused as long as the method has been validated with a widevariety of ignitable liquids with a range of both flash points andpolarity.4. Significance and Use4.1 This practice is useful for preparing extracts from firedebris for later analysis by gas chromatography-mass spec-trometry (GC-MS), see Test
14、 Method E1618.1This practice is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition approved Aug. 15, 2013. Published September 2013. Originallyapproved in 1991. Last previous edition approved in 2
15、007 as E1413 07. DOI:10.1520/E1413-13.2For 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 standards Document Summary page onthe ASTM website.Copyright ASTM Internat
16、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 This is a very sensitive separation procedure, capable ofisolating quantities smaller than 0.1 L of ignitable liquidresidue from a sample4.2.1 Actual recovery will vary, depending on severalfactors, includ
17、ing adsorption temperature, container size, andcompetition from the sample matrix.4.3 This is a potentially destructive technique. Portions ofthe sample subjected to this procedure may not be suitable forre-sampling. Therefore, a portion of the sample extract shouldbe saved for potential future anal
18、ysis. Consider using passiveheadspace concentration as described in Practice E1412.5. Apparatus5.1 Positive Pressure Apparatus:5.1.1 Sample Pressurization DeviceA system capable ofdelivering pressurized dry nitrogen (or other inert gas) at up to40 psi (276 kPa) to an orifice to be inserted into the
19、bottom ofthe sample container.5.1.1.1 A needle valve capable of fine control of the flowrate of the dry nitrogen, at up to 1500 cc/min.5.1.1.2 A flow meter capable of measuring the flow of drynitrogen through the end of the adsorption tube at the rate of 0to 1500 cc/min.5.1.1.3 Container ClosureAdev
20、ice suitable for sealing thecontainer and directing the effluent nitrogen (or other inert gas)and vapors to the adsorption tube.5.2 Negative Pressure Apparatus:5.2.1 Inlet and Outlet SystemA tube containing approxi-mately 1 cm of charcoal is fitted into the lid of the originalcontainer with a suitab
21、le penetrable seal. This serves as a filterfor incoming room air. A vacuum is pulled on an adsorptiontube also fitted into the lid of the original container with asuitable penetrable seal.5.2.2 A vacuum system capable of pulling between 200 and1500 cc/min on the sample collection tube.5.2.3 A flow m
22、eter capable of measuring the flow of airthrough the end of the charcoal tube at the rate of 200 to 1500cc/min.5.3 Thermal Desorption Apparatus:5.3.1 Sampling SystemAn air-tight syringe is connected tothe back-end of a Tenax tube. The front end of the Tenax tubeis fitted into the heated container.5.
23、3.2 In order to prevent leakage and contamination, thesystem should be designed to minimize loss of vapors from thecontainer. For example by means of a septum mounted on topof the lid of the container.5.3.3 Thermal Desorption DeviceA system capable ofdesorbing the volatiles by means of elevated temp
24、erature andtrapping the volatiles in a cold-trap. This apparatus is directlycoupled to a GC-MS.5.4 Adsorption Tubes:5.4.1 Charcoal TubesSuitable charcoal filter and sampleadsorption tubes may be made by inserting a small (approxi-mately 1 cm) plug of glass wool or cotton in the bottom of aPasteur pi
25、pette (approximately 5 mm diameter), then adding2.5 to 5 cm of activated charcoal, and finally, holding thecharcoal in place with an additional plug of glass wool orcotton.5.4.1.1 Alternatively, charcoal tubes are available fromcommercial sources.5.4.2 Tenax TubesSuitable Tenax tubes are commerciall
26、yavailable. Note that solvent extraction of these tubes results incomplications in the desorbing phase because certain solventscause the dissolution of the Tenax. Tenax should be employedwhen thermal desorption is to be performed.5.5 Heating SystemA heating mantel designed to fit theevidence contain
27、er or an oven or a hot plate.5.5.1 An oven may be set up with any number of stations toallow for multiple sample preparation.5.6 Temperature Measuring DeviceA thermometer orthermocouple capable of measuring temperatures in the rangeof 40 to 150C.6. Reagents and Materials6.1 Purity of ReagentsReagent
28、 grade or better chemicalsshall be used in all tests. Unless otherwise indicated, it isintended that all reagents conform to the specifications of theCommittee on Analytical Reagents of the American ChemicalSociety where such specifications are available.3Other gradesmay be used, provided it is firs
29、t ascertained that the reagent isof sufficiently high purity to permit its use without lesseningthe accuracy of the determination.6.2 Solid Adsorbent:6.2.1 Activated Charcoal (coconut).6.2.1.1 Charcoal may be activated and cleaned by heating ina 400C oven for approximately 4 hours and cooling in ade
30、siccator.6.2.1.2 Test each new or reconditioned batch of charcoal forresidual hydrocarbons by analyzing a concentrated extract ofblank adsorption media according to Test Method E1618.6.2.2 Tenax:6.2.2.1 Tenax may be cleaned and conditioned according tothe manufacturers instructions.6.2.2.2 Test each
31、 new or reconditioned batch of Tenax forresidual hydrocarbons by analyzing a concentrated extract ofblank adsorption media according to Test Method E1618.6.3 Glass Wool, or cotton, free of extractable hydrocarbons.6.4 Extraction solvent (for example, carbon disulfide,pentane, ethyl ether).6.4.1 Read
32、 and follow the safety precautions described inthe Safety Data Sheets (SDS) of the extraction solvent that isused.6.4.2 Test each new lot number of the extraction solvent byanalyzing a concentrated portion according to Test MethodE1618.3Reagent Chemicals, American Chemical Society Specifications, Am
33、ericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (
34、USPC), Rockville,MD.E1413 1326.5 Pasteur pipettes and glass vials free of extractablehydrocarbons.7. Sample Preparation7.1 Observe the appropriate procedures for handling anddocumentation of all submitted samples (Guide E1459 andPractice E1492).7.1.1 Examine the fire debris sample in order to determ
35、inethat it is consistent with its description.7.1.1.1 Resolve any discrepancies between the submittingagents description of the evidence and the analysts observa-tion with the submitting agent prior to the completion of thereport.7.2 This is a potentially destructive technique. Portions ofthe sample
36、 subjected to this procedure may not be suitable forre-sampling. Therefore, a portion of the sample extract shouldbe saved for potential future analysis. Consider using passiveheadspace concentration as described in Practice E1412 whichis essentially nondestructive.7.3 The system should be designed
37、so that the majority ofthe samples can be extracted from the container in which theyare delivered to the laboratory.7.3.1 Alternatively, the sample or a portion of the samplecan be placed in an appropriate, clean sampling containerwhich is designed to be flushed by positive or negativepressure.8. Ad
38、sorption Procedure8.1 A laboratory typically has one method of adsorption andelution that is employed. The most common combinations inuse are charcoal adsorption followed by solvent elution, andTenax adsorption followed by thermal desorption. Both adsor-bents can be collected using either a positive
39、 or a negativepressure system. Other solid adsorbents and collection systemscan be used as long as the method has been validated with awide variety of ignitable liquids with a range of both flashpoints and polarity.8.1.1 The volume of air sampled is generally less whenthermal desorption is employed
40、as the entire collected sampleis commonly injected into the GC-MS system for analysis.8.1.2 With thermal desorption there is typically no materialthat can be archived once GC-MS analysis has been performed.If archival of a portion of the sample extract is needed, then adifferent adsorbent and elutio
41、n combination should be choseneither following this practice, or following one of the othersample collection methods for fire debris analysis (PracticesE1386 or E1412). Some instrument manufacturers now havethe facility to collect the unused sample from the split; if yourinstrument has such capabili
42、ty, then there will be materialavailable for archival when thermal desorption is used.8.2 Positive Pressure:8.2.1 Place the sample container in the heating system andconnect to the inert gas source (commonly nitrogen) which willintroduce the gas into the bottom of the container, then connectthe exha
43、ust line to the adsorbing tube.8.2.1.1 Direct connection of the adsorption tube to thesample container is possible, unless an oven is used. Placementof the adsorption tube outside the oven requires the use of anintervening line which must be carefully cleaned between usesto remove any adsorbed or co
44、ndensed residues.8.2.2 PressurizationDeliver the inert gas to the samplethrough a18 in. (3.2 mm) line on the inlet side of the containerat a pressure of 40 psig (276 kPa) upstream of the needle valvecontrolling the flow rate. Connect a14 in. (6.35 mm) line on thedownstream side of the container to t
45、he charcoal tube. Attachthe flow meter to the outlet side of the charcoal tube, and usethe needle valve to adjust the flow to the rate determined to beoptimum for this system.8.2.2.1 Determine the optimum system conditions (flowrate, temperature and time) by placing known quantities ofgasoline, kero
46、sene, mineral spirits, and diesel fuel onto exem-plar substrate material such as squares of carpeting or filterpaper. Determine the percent recovery by gas chromatographicanalysis. The conditions resulting in the highest percent recov-ery is the optimum.8.2.2.2 Remove the flow meter once the flow is
47、 adjusted.Check the flow at least once after the sample has reached thefinal temperature.8.2.3 Place the temperature measuring device in an appro-priate location for the system used in order to monitor thetemperature of the sample. Turn on the heating system andincrease the temperature to no more th
48、an 150C. At thistemperature, most petroleum distillates can be volatilized inless than one hour, and there will be a minimum of pyrolysis ofcommon polymers.8.2.3.1 Allow 20 min for the sample to reach temperature,and an additional one hour flushing the sample out. At thispoint, turn off the gas. The
49、 charcoal adsorption tube is nowready for elution.8.2.3.2 The adsorption time may be reduced if it can beshown that equal or superior recovery rates are achieved in thereduced time period.8.3 Negative Pressure:8.3.1 Place the inlet air filtering adsorption tube and theoutlet adsorption tubes in the lid of the evidence container.8.3.2 Place the temperature measuring device in an appro-priate location for the system used in order to monitor thetemperature of the sample.8.3.3 Apply a vacuum to the sample adsorption tube. Theflow through the tube should be between
