低含量正构烷烃单体碳同位素的尿素络合法分离—同位素质谱分析方法研究
发布时间：2018-09-11 11:51
【摘要】：尿素络合法和5A分子筛法是常用的分离富集环境样品中正构烷烃的方法。尿素络合法步骤多、流程长,每部分处理流程中都可能损失部分正构烷烃,5A分子筛法受环境影响较大,两种方法对于低含量正构烷烃的回收率普遍较低。本研究通过优化尿素络合法的络合条件(尿素用量、络合反应时间、络合反应溶剂、萃取溶剂等),减小了前处理流程中正构烷烃的损失,较大幅度提高了正构烷烃的回收率,建立了尿素络合法分离-气相色谱/同位素质谱分析样品中低含量正构烷烃单体碳同位素的方法。优化的实验流程为:采用正己烷-丙酮溶解样品,加入2ml尿素-甲醇饱和溶液,放置于4℃冰箱中反应48h;制备的尿素络合物用去离子水溶解,加入正己烷后分离出有机相和水相,分别用正己烷、丙酮-正己烷萃取有机相和水相中的正构烷烃,气相色谱法(GC)测定正构烷烃含量,气相色谱-气体同位素质谱法(GC-C-IRMS)测定正构烷烃单体碳同位素。低含量中长链正构烷烃(C19~C40)的回收率达79%~104%,高于5A分子筛法和已有尿素络合法分离富集低浓度中长链正构烷烃的回收率;正构烷烃单体碳同位素的分析精度为0.09%~0.63%(1σ)。利用建立的尿素络合法分析实际样品,能大幅降低未分峰和共流出的干扰,获得良好的净化效果,提高了实际样品中低含量正构烷烃的回收率,尤其能够满足环境样品中的低含量中长链正构烷烃的单体碳同位素分析要求。
[Abstract]:Urea complexation method and 5A molecular sieve method are common methods for separation and enrichment of normal alkanes in environmental samples. There are many steps in urea complexation process and the process is long. The partial loss of n-alkane and 5A molecular sieve process may be affected by the environment in each part of the process. The recovery rate of the two methods for low-content n-alkanes is generally low. By optimizing the complexation conditions of urea complexation (urea dosage, complexation time, complexation solvent, extraction solvent, etc.), the loss of n-alkanes in the pretreatment process was reduced, and the recovery rate of n-alkanes was greatly increased. A method for the determination of carbon isotopes of low and low content n-alkane monomers by urea complexation and gas chromatography / isotope mass spectrometry was established. The optimized experimental process was as follows: the sample was dissolved with n-hexane-acetone, the saturated solution of 2ml urea-methanol was added, and the prepared urea complex was dissolved in deionized water at 4 鈩，
本文编号：2236613
[Abstract]:Urea complexation method and 5A molecular sieve method are common methods for separation and enrichment of normal alkanes in environmental samples. There are many steps in urea complexation process and the process is long. The partial loss of n-alkane and 5A molecular sieve process may be affected by the environment in each part of the process. The recovery rate of the two methods for low-content n-alkanes is generally low. By optimizing the complexation conditions of urea complexation (urea dosage, complexation time, complexation solvent, extraction solvent, etc.), the loss of n-alkanes in the pretreatment process was reduced, and the recovery rate of n-alkanes was greatly increased. A method for the determination of carbon isotopes of low and low content n-alkane monomers by urea complexation and gas chromatography / isotope mass spectrometry was established. The optimized experimental process was as follows: the sample was dissolved with n-hexane-acetone, the saturated solution of 2ml urea-methanol was added, and the prepared urea complex was dissolved in deionized water at 4 鈩，
本文编号：2236613
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