样品前处理过程中多环芳烃的稳定碳同位素分馏
Stable Carbon Isotope Fractionation of Polycyclic Aromatic Hydrocarbons During the Sample Preparation Process
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摘要: 利用多环芳烃标准样品连续和穿插进样相结合的方式,检验了气相色谱-燃烧-同位素比质谱仪(GC-C-IRMS)测定多环芳烃单体碳同位素比值(δ13C)的稳定性和准确性,观察了测定过程中色谱柱的分离效果。结果表明,出峰面积和分离程度是影响化合物δ13C平行性的主要原因。通过多次实验,分析了样品前处理过程中多环芳烃各个化合物稳定碳同位素的分馏情况,包括凝胶渗透色谱(GPC)和硅胶柱等净化过程,以及旋转蒸发和氮气吹扫等浓缩过程。实验表明,各前处理过程中样品内多环芳烃的稳定碳同位素分馏均不明显,其中硅胶柱净化过程相比GPC过程对样品中多环芳烃的δ13C影响较大,但总体上仍未超过未处理标样δ13C值的2倍标准偏差范围。旋转蒸发和氮吹过程对样品中多环芳烃的δ13C影响程度相当,都位于未处理标样δ13C值1倍标准偏差以内的水平。Abstract: Stability and accuracy for determination of δ13C of polycyclic aromatic hydrocarbons (PAHs) were tested by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) with continuous and intermittent injection modes. The results showed that the peak area and peak separation degree were the main factors influencing the precision of δ13C data. The fractionation of stable carbon isotopes of PAHs during the sample pretreatment processes was also tested. The cleanup process with gel permeation chromatography (GPC), silica gel column, as well as rotatory evaporation, nitrogen purge and other enrichment process brought no significant isotope fractionation of PAHs. Isotope fractionation in cleanup processes with silica gel column was little larger than with GPC, but still within two standard deviation (2σ) range of the mean δ13C of PAHs from an unprocessed standard material. And the enrichment processes of rotatory evaporation and nitrogen purge produced a little isotope fractionation for all the measured δ13C of PAHs within 1σ range of the mean δ13C from the unprocessed standard material.
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Keywords:
- polycyclic /
- aromatic /
- hydrocarbon /
- sample
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