Determination of nitrophenolic compounds from atmospheric particles using hollow-fiber liquid-phase microextraction and capillary electrophoresis/mass spectrometry analysis.

A hollow-fiber liquid-phase microextraction method was developed to enrich nine nitrophenolic compounds from aqueous extracts of atmospheric aerosol particles. Analysis was performed by CE coupled with ESI MS. The BGE composition was optimized to a 20 mM ammonium acetate buffer at pH 9.7 containing 15% methanol v/v. Several extraction parameters (composition of organic liquid membrane, pH of acceptor phase, salting-out effect, extraction time) were investigated for their effect on the analyte recoveries. The donor phase consisted of a 1.8 mL sample solution kept at pH 2 while the acceptor phase was a 15 μL 100 mM aqueous ammonia solution. Dihexyl ether served as supported liquid membrane. Low detection limits in the range of nanomole per liter were achieved. Recoveries of aqueous standard solutions were found to be between 11 and 90% with enrichment factors between 10 and 100. Interday and intraday repeatabilities were in an acceptable range for most compounds (6-15% and 7-10%, respectively) but somewhat higher for 4-nitrocatechol (59 and 48%) and 2-nitrophenol (17 and 35%). The developed method was found to be competitive with more established method and was successfully applied to samples of atmospheric particulate matter from field experiments.