Derivatization of Levoglucosan for Compound-Specific delta C-13 Analysis by Gas Chromatography/Combustion/Isotope Ratio Mass Spectrometry

Levoglucosan is a thermal decomposition product of cellulose in particulate matter. delta C-13 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 degrees 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 parts per thousand. The standard deviation of measured delta C-13 value of levoglucosan was between 0.22 and 0.48 parts per thousand. The method was applied to particle samples collected from the combustion of cellulose at four different temperatures. delta C-13 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-13 enriched in levoglucosan during the combustion process.