甲基硼酸衍生法测定丁四醇中的碳同位素

Determination of Stable Carbon Isotope in Tetritols by Methylboronic Acid Derivatization

对赤藻糖醇和苏阿糖醇进行甲基硼酸衍生化,并对反应物和生成的环状硼酸酯衍生产物进行稳定碳同位素测定。采用元素分析/同位素比质谱(EA/IRMS)对固体赤藻糖醇、苏阿糖醇、甲基硼酸的碳同位素的测定和气相色谱/燃烧/同位素比质谱(GC/C/IRM)对硼酸酯衍生产物的同位素测定的结果表明,当衍生化反应温度为60℃,反应时间为60min,甲基硼酸和四醇化合物的摩尔比为10∶1时,通过反应物的同位素值及质量平衡关系计算而得的硼酸酯的δ13C数值和实际测定的产物的碳同位素之间的差异小于0.5‰,在该衍生化反应过程中不存在同位素分馏。此外,在GC/MS上,对赤藻糖醇、苏阿糖醇、2-甲基赤藻糖醇、2-甲基苏阿糖醇的甲基硼酸酯衍生产物进行确认,为进一步对天然源气溶胶中的2-甲基丁四醇进行稳定碳同位素分析提供实验基础。

Tetritols including erythritol and threitol were derivatized by methylboronic acid（MBA） , and the stable carbon isotopic compositions of reactants（ tetritols and MBA） and resultants（ the ringed boronate derivatives） were determined. The δ^13C value of solid erythritol, threitol and MBA were measured by elementalanalysis/isotope ratio mass spectrometry（EA/IRMS） , the δ^13C value of methylboronate derivatives were measured by gas chromatography/combustion/isotope ratio mass spectrometry （GC/C/IRMS）. Experimental results illustrated that when derivatization temperature was 60 ℃ , derivatization time was 60 min, the molar ratio of MBA to tetritol was 10：1 , the difference between δ^13C of methylboronate calcultated by δ^13C of reactants and mass balance equation with determined δ^13C of methylboronate was less than 5% , there not existed isotopic fractionation in this derivatization reaction. Moreover, the structure of methylboronate derivatives of erythritol, threitol, 2-methylerythritol and 2-methyhhreitol were discussed. These will provide the base for stable carbon isotopic determination of 2-methyltetrols in natural aerosol.