GC-MS analysis of low-molecular-weight dicarboxylic acids in atmospheric aerosol: comparison between silylation and esterification derivatization procedures.

This paper describes methods for the determination of low-molecular-weight (LMW) dicarboxylic acids in atmospheric aerosols as important chemical tracers for source apportionment of aerosol organics and for studying atmospheric processes leading to secondary organic aerosol formation. The two derivatization procedures most widely used in GC analysis of dicarboxylic acids were compared: esterification using BF(3)/alcohol reagent and silylation using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The advantages and drawbacks of the two methods are investigated and compared in terms of (1) precision and accuracy of the results and (2) sensitivity and detection limit of the procedure. The comparative investigation was performed on standard solutions containing target C(3)-C(9) dicarboxylic acids and on experimental particulate matter (PM) samples. Attention was focused on low-volume sampling devices that collect small amounts of sample for organic speciation. The results show that, overall, both the techniques appear suitable for the analysis of LMW dicarboxylic acids in atmospheric aerosols since they provide low detection limits (< or = 4 ng m(-3)) and satisfactory reproducibility (RSD% < or = 15%). Between them, BSTFA should be the reagent of choice under the most limiting conditions of PM filters collected by low-volume air samplers: It provides determination of all the target C(3)-C(9) dicarboxylic acids with lower detection limits (< or = 2 ng m(-3)) and higher reproducibility (RSD% < or = 10%).