二烯橡胶燃烧残留物对火场汽油检验鉴定的干扰

Influence of Diene Rubber Combustion Residue on the Identification of Gasoline in Fire Debris

  • 摘要: 放火案件中汽油等助燃剂的检验一直是物证鉴定领域的难点。为研究二烯橡胶燃烧残留物对汽油检验鉴定的干扰程度,利用气相色谱-质谱(GC-MS)技术研究顺丁橡胶、丁基橡胶和丁苯橡胶3种典型二烯橡胶及其加载不同量汽油后的燃烧残留物。结果表明,在加载汽油前后的3种橡胶样品的燃烧残留物中均检出烷烃类、烯烃/环烷烃类、烷基苯类、茚满类、稠环芳烃类及多环芳烃类特征组分,对汽油的检验鉴定具有强干扰性。向5 g橡胶样品中分别加载0.05、0.1 mL汽油进行混合燃烧,所得燃烧残留物中烷基苯类和茚满类特征组分所对应的特征峰数量和相对峰面积比例有不同程度的改变,其中烷基苯类组分的变化较典型。本研究可为存在二烯橡胶基质的火场汽油检验鉴定提供参考和依据。

     

    Abstract: The identification of accelerant about gasoline and other ignited liquids in arson has always been a difficult problem in the field of physical evidence identification. How to avoid “false positive” and “false negative” results is a key issue. To study the interference of diene rubber on gasoline identification from two aspects of “false positives” and “false negatives”, and to explore its degree when gasoline was mixed with diene rubber in different proportions, the combustion residues obtained from cis-polybutadiene rubber, isobutylene isoprene rubber and styrene butadiene rubber after loading different amounts of gasoline were compared using gas chromatography-mass spectrometry (GC-MS). The results showed that alkanes, alkenes/cycloalkanes, aromatic-alkylbenzenes, homologs of indenes and indanes, alkylnaphthalenes and polycyclic aromatic hydrocarbons were detected in the combustion residues of the three kinds of diene rubber samples before and after gasoline loading, which was consistent with gasoline in terms of the characteristic components categories and had strong interference with gasoline identification. After loading 0.05 mL and 0.1 mL gasoline respectively into 5 g rubber sample, there was no significant changes in the characteristic components of cycloalkanes/alkenes, alkylnaphthalenes, and polycyclic aromatic hydrocarbons in the rubber combustion residues. The number and relative peak area ratio of characteristic peaks corresponding to aromatic-alkylbenzenes, homologs of indenes and indanes changed to different degrees, while the changes of alkylbenzenes were more representative. Loading gasoline or not had little effect on the ratio of the characteristic peaks of C2 benzene components in the combustion residues of cis-polybutadiene rubber. The ratio among three characteristic peaks of C2 benzene components in the combustion residues of isobutylene isoprene rubber and styrene butadiene rubber samples changed significantly when the gasoline loading amount reached 0.1 mL. This study can provide important references for the gasoline identification when there is a presence of diene rubber matrix in practical work.

     

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