Study of acidified ignitable liquid residues in fire debris by solid‐phase microextraction with gas chromatography and mass spectrometry

The detection and identification of ignitable liquid residues in fire debris can be meaningful in fire investigations. However, background pyrolysis products and weathering hinder the identification and classification steps. In addition to those processes, the acidification of the ignitable liquids before the combustion process could make those tasks even more difficult. Nevertheless, there are no systematic studies assessing the extraction, analysis, and composition of acidified ignitable liquid residues obtained from fire debris. In this work, a method for the study of acidified ignitable liquid residues in fire debris by solid‐phase microextraction with gas chromatography and mass spectrometry is proposed. This methodology has been evaluated, first with simulated solutions (gasoline/sulfuric acid mixtures set on fire under controlled conditions), and then with analysis of samples from real fire debris obtained from 18 chemical ignition Molotov cocktails made with sulfuric acid and three different ignitable liquids (two types of gasoline and diesel fuel). In addition, the extensive modifications observed in chromatograms of acidified ignitable liquid residues regarding neat and weathered samples were studied. These alterations were produced by the combustion and acidification processes. As a consequence, tert‐butylated compounds are proposed as diagnostic indicators for the identification of acidified gasoline in fire debris, even in strongly weathered samples.     

UPLC-DAD法同时测定预调鸡尾酒中24种水溶性合成色素

建立了预调鸡尾酒中24种水溶性合成色素的超高效液相色谱-二极管阵列检测器(UPLC-DAD)分析方法,对流动相、色谱柱、洗脱梯度等色谱条件进行了优化,确定最佳分离条件为:Waters BEH C18色谱柱(2. 1 mm×50 mm,1. 7μm),流动相为10 mmol/L乙酸铵(pH 6. 25)和甲醇-乙腈(2∶8,体积比),采用梯度洗脱,在16 min内实现24种色素的快速分离。24种色素在0. 01～50. 0 mg/L范围内具有良好的线性关系(r~2 0. 998 0),方法检出限为0. 66～27. 78μg/L,定量下限为2. 19～92. 59μg/L;日内相对标准偏差(RSD)为0. 04%～5. 3%,日间RSD为0. 08%～6. 4%;回收率为53. 4%～114%。该方法具有所测色素种类多、分析时间短、检出限低等优势,已成功应用于市售预调鸡尾酒样品的检测。