Zhang Dongling, Swe Aung Swe, Han Yong, Zhang Yanlin, Chen Yingjun, Li Hongli, Yu Feifei, Wang Yangjun, Feng Jialiang, Wang Wu
Institute of Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University, 200444 Shanghai, China.
Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science and Technology, 210044 Nanjing, China.
Int J Anal Chem. 2020 Jul 26;2020:9571969. doi: 10.1155/2020/9571969. eCollection 2020.
Levoglucosan is a thermal decomposition product of cellulose in particulate matter. C value of levoglucosan could be used in studying the combustion mechanisms and chemical pathways. In order to introduce a minimum number of carbon atoms, based on the stereostructure of levoglucosan, a two-step derivatization method with methylboronic acid and MSTFA was developed and carefully optimized. The recommended reaction temperature is 70°C; the reaction time is 60 min for MBA and 120 min for MSTFA derivatization; and the molar ratio of levoglucosan : MBA : MSTFA is 1 : 1: 100 and 1 : 1: 120 and the reagent volume ratio of MSTFA : pyridine is between 1 : 3 and 1 : 4. The developed method achieved excellent reproducibility and high accuracy. The differences in the carbon isotopic compositions of the target boronate trimethysilylated derivative between the measured and calculated ranged from 0.09 to 0.36‰. The standard deviation of measured C value of levoglucosan was between 0.22 and 0.48‰. The method was applied to particle samples collected from the combustion of cellulose at four different temperatures. C values of levoglucosan in particle samples generated from a self-made combustion setup suggesting that combustion temperature play a little role on isotope fractionation of levoglucosan, although C enriched in levoglucosan during the combustion process.
左旋葡聚糖是颗粒物中纤维素的热分解产物。左旋葡聚糖的C值可用于研究燃烧机制和化学途径。为了引入最少数量的碳原子，基于左旋葡聚糖的立体结构，开发并仔细优化了一种用甲基硼酸和MSTFA的两步衍生化方法。推荐的反应温度为70°C；MBA衍生化的反应时间为60分钟，MSTFA衍生化的反应时间为120分钟；左旋葡聚糖∶MBA∶MSTFA的摩尔比为1∶1∶100和1∶1∶120，MSTFA∶吡啶的试剂体积比在1∶3至1∶4之间。所开发的方法具有出色的重现性和高准确性。目标硼酸三甲硅烷基化衍生物的碳同位素组成测量值与计算值之间的差异范围为0.09至0.36‰。左旋葡聚糖测量C值的标准偏差在0.22至0.48‰之间。该方法应用于从四个不同温度下纤维素燃烧收集的颗粒样品。自制燃烧装置产生的颗粒样品中左旋葡聚糖的C值表明，尽管燃烧过程中左旋葡聚糖中C富集，但燃烧温度对左旋葡聚糖的同位素分馏作用不大。
