气相色谱-质谱法测定汽油中醇类、醚类和酯类添加剂

目前市场上一些加油站中存在着在汽油中非法添加一些醇类、醚类、酯类氧化物添加剂的现象,对车辆的机动性、安全性和环保性存在潜在危害。实验建立了气相色谱-质谱法测定汽油中19种醇类、醚类和酯类添加剂含量的分析方法。通过试验优化了色谱分析的主要条件,确定了最佳分流比为1∶100,溶剂为正十一烷,稀释倍数10～100倍,同时研究了溶剂的切换时间。利用选择离子法(SIM)确定定量离子和参考离子,可以有效消除汽油中复杂成分对目标组分的影响。以各目标组分的峰面积对其相应的质量浓度作图,发现甲醇、乙醇质量浓度在5.0～100.0 mg/L、其他化合物质量浓度在1.0～20.0 mg/L范围内线性良好,校准曲线的线性相关系数在0.998 6~0.999 9之间。各组分的检出限为0.5~1.0 mg/L。对添加了标准溶液的实际样品进行精密度和正确度考察,19种组分测定结果的相对标准偏差(RSD,n=8)为2.1%～6.2%,回收率为85%～108%。对市售92#、95#、98#常见标号汽油样品进行测定,结果发现部分汽油中含有甲醇、甲基叔丁基醚(MTBE)、乙酸仲丁酯等氧化物添加剂,质量浓度在20~1 200 mg/L之间。

Determination of alcohol,ether and ester additives in gasoline by gas chromatography mass spectrometry

At present,some alcohol, ether and ester additives were illegally added into gasoline in some gasoline stations, which resulted in potential hazards to the maneuverability, safety and environmental protection of vehicles. In response to this phenomenon, the analysis method of 19 types of alcohol, ether and ester additives in gasoline was established by gas chromatography mass spectrometry. The main analytical conditions were optimized by experiments. The optimal split ratio was 1∶100. The solvent was n-undecane and the dilution factor was 10-100. Meanwhile, the switch time of solvent was also investigated. The quantification ion and reference ion were determined by selected ion method (SIM), which could effectively eliminate the influence of complex components on target components in gasoline. The peak area of each target component against the corresponding mass concentration was plotted. It was found that the linearity was good when the mass concentration of methanol and ethanol was in range of 5.0-100.0 mg/L, and the mass concentration of other compounds was in range of 1.0-20.0 mg/L. The linear correlation coefficients of calibration curves were between 0.998 6 and 0.999 9. The detection limits of components were between 0.5 mg/L and 1.0 mg/L. The precision and accuracy tests of actual samples containing standard solution were performed. The relative standard deviations (RSD, n=8) of 19 components were between 2.1% and 6.2%, and the recoveries were in range of 85%-108%. The common gasoline samples (92#, 95# and 98#) were determined according to the experimental method. It was found that some samples contained oxide additives such as methanol, methyl tertiary butyl ether (MTBE) and sec-butyl acetate. The mass concentration was in range of 20-1200 mg/L.