气相色谱-场电离飞行时间质谱测定中间馏分油中链烷烃的形态分布

利用气相色谱-场电离飞行时间质谱技术( GC-FI TOF MS)建立了中间馏分油中不同异构程度链烷烃的碳数分布表征方法。首先利用GC-FI TOF MS技术对不同异构程度的链烷烃进行分离、鉴别,然后建立了中间馏分油沸点范围内正构烷烃、异构烷烃在GC-FI TOF MS测定时的相对响应因子算法及不同异构程度链烷烃的碳数分布算法,最后考察此定量方法的精密度和准确度。结果表明,GC-FI TOF MS可以将同碳数链烷烃区分为异构程度不同的3部分：多取代基异构烷烃、单取代基异构烷烃和正构烷烃；可利用GC-FI TOF MS对异构程度不同的链烷烃进行定量分析,精密度较好,相对偏差小于15%。此方法无需进行样品预分离,可直接进样分析,缩短了分析时间,且首次提供了不同异构程度异构烷烃的碳数分布信息。

Paraffins Species Distribution Analysis in Petroleum Middle Fractions by GC Field Ionization Time-of-Flight Mass Spectrometry

A gas chromalography field ionization time-of-flight mass spectrometric ( GC-FI TOF MS ) technology was used to characterize the carbon number distribution of paraffins with different levels of isomerization in petroleum middle fractions. Firstly, with GC-FI TOF MS, the paraffins with different levels of isomerization were identified. Secondly, the relative response factors of normal paraffins and iso-paraffins were determined and their quantitative analysis methods were established. Finally, the accuracy and precision of the method were examined. The results indicated that paraffins with the same carbon number could be divided into poly-substituted iso-paraffins, mono-substituted iso-paraffins and normal paraffins by GC-FI TOF MS. The quantitation of paraffins with different levels of isomerization could be obtained. The accuracy and precision were acceptable. The sample pre-separation was not required which greatly shortened the analysis time. The analysis provides the information for the carbon number distribution of iso-paraffins with different levels of isomerization.