大气丙酮碳同位素组成测定方法的研究

Determination of the Carbon Isotope Composition of Atmospheric Acetone

利用气相色谱/燃烧/同位素比值质谱(GC/C/IRMS)分析技术,研究了具有不同碳同位素组成的丙酮与衍生剂2,4-二硝基苯肼(DNPH)的液相反应及其相应的气相反应实验过程中的碳同位素效应,探讨了以该方法测定大气丙酮碳同位素组成的可行性。研究结果表明,在衍生化过程中不会产生碳同位素分馏。本实验通过测定衍生剂DNPH与相应的衍生物的碳同位素值,大气中丙酮碳同位素组成通过质量平衡方程计算而求得。采用该方法对大气丙酮碳同位素组成的初步测定结果表明,具有相同排放源的大气丙酮碳同位素比值基本不变。本方法实验重现性好,测定精度高,可以用于分析大气丙酮的排放源研究。

A method was developed for the determination of carbon isotope composition of atmospheric acetone using gas chromatography/combustion/isotope ratio mass spectrometry （GC/C/IRMS）. Through acetone via 2,4-dinitrophenylhydrazine （DNPH） derivatization, it was found that isotope fractionation values were so little as to be ignored during the whole reaction process, the derivatization process showed that no carbon isotope fractionation occurred for acetone within the precision limits of the GC/C/IRMS system （ 〈0.50 ‰）. By determining carbon isotopic compositions of DNPH and acetone-DNPH derivative, the δ^13C values of atmospheric acetone could be calculated through a mass balance. Using the method described above, the result of one sampling site showed that the δ^13C values of atmospheric acetone emitted from the same source are ahnost identical. The excellent accuracy and reproducibility indicated that this method could be used as an effective tool to provide valuable information about different sources of atmospheric acetone.