【国外标准】 Standard Practice for Separation of Ignitable Liquid Residues from Fire Debris Samples by Dynamic Headspace Concentration onto an Adsorbent Tube

5.1 This practice is useful for preparing extracts from fire debris for subsequent qualitative analysis by gas chromatography mass spectrometry, see Test Method E1618.5.2 The sensitivity of this practice is such that a sample consisting of a laboratory tissue onto which as little as 0.1 µL of ignitable liquid has been deposited, in an otherwise empty sample container, will result in an extract that is sufficient for identification and classification using Test Method E1618 (1).5.2.1 Recovery from fire debris samples will vary, depending on factors including debris temperature, adsorbent temperature, container size, adsorptive material, headspace volume, sampling time and flow rate, and adsorptive competition from the sample matrix (2).5.3 The principal concepts of dynamic headspace concentration are similar to those of static headspace concentration (Practice E3189). The dynamic headspace concentration technique can be more sensitive than the static headspace concentration technique. However, sample containers subjected to dynamic headspace concentration could be unsuitable for re-sampling.5.3.1 Dynamic headspace concentration alters the original composition of the test sample because a portion of the original headspace from the sample container is removed and exchanged with dry inert gas or air. A portion of the concentrated headspace sample should be preserved for potential future analysis, if possible and if required, in accordance with Practice E2451.5.4 Common solid adsorbent/desorption procedure combinations in use are activated carbon/solvent elution, and Tenax4 TA/thermal desorption.5.5 Solid adsorbent/desorption procedure combinations not specifically described in this standard can be used as long as the practice has been validated as outlined in Section 11.1.1 This practice describes the procedure for separation of ignitable liquid residues from fire debris samples using dynamic headspace concentration onto an adsorbent tube, with subsequent solvent elution or thermal desorption.1.2 Dynamic headspace concentration onto an adsorbent tube takes place from a closed, rigid sample container (typically a metal can), using a source of dry inert gas or a vacuum system.1.3 Both positive and negative applied pressure systems for dynamic headspace concentration onto an adsorbent tube are illustrated and described.1.4 This practice is suitable for preparing extracts from fire debris samples containing a range of volumes (µL to mL) of ignitable liquid residues, with sufficient recovery for subsequent qualitative analysis (1).21.5 Alternative headspace concentration methods are listed in Section 2 (see Practices E1388, E1412, E3189, and E2154).1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This standard cannot replace knowledge, skills, or abilities acquired through education, training, and experience (Practice E2917) and is to be used in conjunction with professional judgment by individuals with such discipline-specific knowledge, skills, and abilities.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.