Determination of atmospheric amines by on-fiber derivatization solid-phase microextraction with 2,3,4,5,6-pentafluorobenzyl chloroformate and 9-fluorenylmethoxycarbonyl chloride

摘要

Alkylamines play an important role in atmospheric chemistry and are of concern for human health. Determining them from the vapor phase is challenging owing to their high polarity and volatility, water solubility, low concentrations, and poor chromatographic properties. We propose on-fiber derivatization solid-phase microextraction (SPME) to increase sensitivity and selectivity for the determination of alkylamines in air samples. SPME fibers coated in head-space with 2,3,4,5,6-pentafluorobenzyl chloroformate (PFBCF, 10 min) or 9-fluorenylmethoxycarbonyl (FMOC) chloride (5 min) were exposed to the sample for 5-120 min, after which the derivatized alkylamines were thermally desorbed in the GC injection port and analyzed by GC-MS. The specific focus of the research was dimethylamine (DMA) but, as well as secondary amines, both coating agents readily react with primary and tertiary amines and with ammonia at ambient temperatures. The fiber coating procedures, sampling times, and analytical conditions were optimized, and methods were tested with natural samples. PFBCF was more selective and almost an order of magnitude more sensitive than FMOC chloride. Both reagents are applicable, however, depending on the requirements. With scan mode and use of molecular ion for quantification, the limit of quantification for DMA was 0.17 mu g L-1 when derivatized with PFBCF and 3.4 mu g L-1 when derivatized with FMOC chloride. When selected ion monitoring was used with the most abundant ion, the limit of quantification for DMA was 2.8 ng L-1. Intermediate reproducibility expressed as relative standard deviation was around 30% with PFBCF and less than 20% with FMOC chloride. Fibers coated with PFBCF could be used at least up to 24 h when stored at 4 degrees C and for 5 to 7 h when stored at room temperature. After sampling/derivatization, storage time before analysis should not exceed 48 h at 4 degrees C or 24h at room temperature. At maximum, the PFBCF-coated fiber can be used in 100 coating/sampling/analysis cycles. (C) 2014 Elsevier By. All rights reserved.