柴油机排气微粒中多环芳香烃的色谱质谱分析

Analysis of PAHs in Particulate Matter of a Diesel Engine by Gas Chromatography-Mass Spectrometry

柴油机颗粒物中的多环芳烃多被碳层所包围，且颗粒物中的有机可溶成分组分多，造成柴油机颗粒物中的多环芳烃分析难度大。通过多次试验，采用索式与超声萃取相结合的方式对7款满足国Ⅲ、国Ⅳ排放标准的重型车用柴油机的颗粒物进行了有机可溶成分的有效提取。通过对气相色谱质谱联机设备的进样方式、离子源温度及色谱温度条件的有效优化，建立了以全扫描方式定性、选择离子扫描方式定量分析柴油机颗粒物中16种多环芳烃的方法。对发动机在欧洲稳态循环（ESC）和欧洲瞬态循环（ETC）下排放的颗粒物样品的分析结果表明：国Ⅳ柴油机在ESC循环下的有机可溶成分小于国Ⅲ发动机，国Ⅳ发动机的16种多环芳烃的体积分数排放为国Ⅲ发动机的10％～30％。ETC循环下，国Ⅳ发动机的16种多环芳烃的总排放浓度为国Ⅲ发动机的14％-22％。不同技术路线相同排放水平的发动机在相同工况下的16种多环芳烃排放没有明显差异，国Ⅲ和国Ⅳ柴油机在ETC循环下柴油机尾气中16种多环芳香烃总浓度是ESC循环下的2～3倍。

It is difficult to analyze polycyclic aromatic hydrocarbons （PAHs） in paniculate matter （PM） from diesel engine due to two reasons. One is the difficulty to completely extract PAHs due to carbon surrounding them, another is a large part of soluble organic fraction （SOF） in diesel PM emissions. In this paper, solvent and ultrasonic extraction methods were used to distill the SOF from PM emissions in state stage 3 and 4 diesel engines. By optimization of gas chromatography mass spectrometry equipment in-line sampling methods, ion source and chromatography temperature, a method which could analyse 16 kinds polycyclic aromatic hydrocarbons in diesel paniculate matter was set up through utilization of full-scan mode for qualitative analysis and selected ion scan mode for quantitative analysis. The result showed that SOF fraction of PM emission in stage 4 diesel engine is lower than that of stage 3 engine under ESC test. The volume concentration of 16 PAHs in stage 4 engine is 10%-30% of stage 3 diesel engine. Under ETC test, the percent of PAHs is 14%-22%. There is little difference for PAHs emission between different emis- sion control strategies for diesel engines under comparable emission level at the same operating condition. Total PAHs emission concentrations of stage 3 and 4 diesel engines under ETC test are 2 or 3 times to that of ESC test.