Determination of Haloacetic Acids from Aqueous Samples Collected from the Canadian Environment Using an In Situ Derivatization Technique

Abstract

Abstract Determination of haloacetic acid concentrations in Canadian environmental samples were carried out using an in situ derivatization method. An existing method used to quantitate monochloroacetic acid was extended to analyze simultaneously for 2,4-difluoroanilide of fluoro-, chloro- and bromoacetic acids in aqueous samples. This method requires reduction of sample volume to 50 mL, and then reacting the concentrate with 2,4-difluoroaniline using dicyclohexyl-carboiimide as catalyst in ethyl acetate to produce the acid anilide. Quantitation utilizes gas chromatography with mass selective detector in the selected ion monitoring mode. The response at m/z 129 was used to quantitate the mono-substituted acids and, with the exception of trifluoroacetic acid, the di- and tri-substituted acids were quantitated using m/z 156. Quantitation of trifluoroacetic acid utilized m/z 225. The ubiquitous nature of these compounds required analyzing a blank with each sample as traces of the haloacids were found in the solvent and chemicals used in the method. All nine anilides were synthesized with the response from standard solutions used for quantitation. Environmental samples from 14 locations were analyzed and these included lake water (replicates), rain, snow, groundwater and drinking water samples. With the exception of one groundwater sample, mono- and dichloroacetic acids were found in all samples at concentrations in the range of 0.02 to 8 µg/L. Also mono- and trifluoroacetic acid were found in 9 of 14 and 7 of 14 of the samples, respectively (0.004 to 0.600 µg/L). Monobromoacetic acid was found mainly in the drinking water samples at 4 µg/L. The dibromoacetic acid was detected in snow and drinking water samples, and trichloro- and difluoroacetic acids were detected in only a few samples. Tribromoacetic acid was not detected in any of the samples.