单分子烃碳同位素分析方法及影响因素探讨

The Carbon Isotope Analytical Method for Monomolecular Hydrocarbons and Its Affecting Factors

本文介绍了原油和岩石可溶有机质的单分子烃C同位素分析方法。通过饱和烃样品预处理与未处理、标准样品及其加入异构烷烃后的对比试验以及常见的 3种基线模式数据处理方法的讨论。分析了单分子烃C同位素测定的误差来源 ,阐明了正构烷烃与异构烷烃预分离处理、色谱升温程序和数据处理是影响单分子烃C同位素测定结果的重要因素。指出采用尿素络合法或 5A分子筛吸附法进行样品预分离处理 ,选择单一升温速率或在待测化合物溢出的时间范围内保持较平缓的升温梯度 ,对多拐点基线模式进行分段数据处理等方法可提高分析结果的精度和准确度。

The analytical method for carbon isotopic compositions of monomolecular hydrocarbon in crude oil and sediments is discussed in this paper. Through contrast test of monomolecular δC values between the pretreated alkane sample and the original alkane sample as well as between the n-alkane standard sample and its mixture with i-alkanes,and a discussion on three routine baseline pattern data-processing methods,this paper analyzes the error sources of carbon isotopic compositions of monomolecular hydrocarbon. It is shown that the sample pretreatment for separating n-alkanes from i-alkanes,the chromatogram temperature program and the data treatment have significant effects on the δC values of monomolecular hydrocarbon. This paper points out that such measures as the sample pretreatment for separating n-alkanes from i-alkanes with urea complex or 5A molecule sieving adsorption,the utilization of single temperature rate or the maintenance of gentle temperature gradient during the overflowing of the compound and the sectional data treatment for the multi-inflexion baseline pattern can improve the precision and accuracy of the measurement.