热脱附-GC/MS快速测定大气细颗粒物中支链烷烃和烷基环己烷

建立了直接进样-热脱附-GC/MS法快速测定大气细颗粒物中7种支链烷烃和烷基环己烷类有机示踪物。为提高方法的选择性和灵敏度等指标，优化了脱附温度和时间、冷阱填料和捕集温度。采用了高、低浓度工作曲线，线性范围分别为0.25~50 ng和0.025~0.5 ng，相关系数均在0.990以上，空白加标回收率在86.2%~110%之间，实际样品加标回收率在97.1%~113%之间。当采样体积为24 m³时，各目标化合物的检出限在0.004~0.020 ng/m³之间，低于加速溶剂萃取法的检出限。利用本方法测定了北京城区采暖季和非采暖季PM2.5的实际样品，结果表明，在采暖季和非采暖季样品中，各目标物均有检出，支链烷烃含量比烷基环己烷类化合物高2个数量级，采暖季的支链烷烃和烷基环己烷类化合物的含量均明显高于非采暖季。本方法无需复杂的前处理和有机溶剂，操作简便快捷，在颗粒物中非极性化合物的快速检测方面具有很大的应用价值。

Determination of Branched Alkane and Alkylcyclohexane in Atmospheric Fine Particulate Matter Using Rapid Direct Thermal Desorption-GC/MS

The organic molecular tracers such as branched alkane and alkylcyclohexane in PM2.5 were determined using direct thermal desorption-gas chromatography-mass spectrometry （GC/MS）. In order to improve selectivity and sensitivity of method, various parameters such as desorption temperature, desorption time, cooling trap packing, and cooling temperature were studied. Results showed that the correlation coefficients of organic molecular tracers in the range of 0.25-50 ng and 0.025-0.5 ng are all above 0.990. The recoveries of the target compounds in blank quartz filters and actual particulate matter samples are 86.2%-110% and 97.1%-113%, respectively. Besides, the limits of detection (LODs) of the target compounds are 0.004-0.020 ng/m³ with the sampling volume of 24 m³, which is much lower compared with accelerated solvent extraction method, because of no solvent extraciton and less target compounds loss. The actual samples of PM2.5 collected in heating season and non heating season in Beijing were determined using this method. The results showed that the target compounds are all detected, and the total concentrations of branched alkane and alkylcyclohexane in heating season are significantly higher than that in the non heating season. Besides, the concentration of branched alkane is two orders of magnitude higher than alkylcyclohexane both in heating season and non heating season. This method is simple and fast, and has great application value in the rapid detection of non polar compounds in particulate matter without complicated pretreatment and organic solvent.