Rapid screening of carboxylic acids from waste and surface waters by ESI-MS/MS using barium ion chemistry and on-line membrane sampling
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Issue Date
2016-03
Authors
Duncan, Kyle D.
Volmer, Dietrich A.
Gill, Chris G.
Krogh, Erik T.
License
Subject
Abstract
Negative ion tandem mass spectrometric analysis of aliphatic carboxylic
acids often yields only non-diagnostic ([M-H]-) ions with limited selective
fragmentation. However, carboxylates cationized with Ba2+ have demonstrated
efficient dissociation in positive ion mode, providing structurally diagnostic
product ions. We report the application of barium adducts followed by collision
induced dissociation (CID), to improve selectivity for rapid screening of carboxylic
acids in complex aqueous samples. The quantitative MS/MS method presented
utilizes common product ions of [M-H+Ba]+ precursor ions. The mechanism of product ion formation is investigated using isotopically labeled standards and a
series of structurally related carboxylic acids. The results suggest that hydrogen
atoms in the β and γ positions yield common product ions ([BaH]+ and [BaOH]+).
Furthermore, the diagnostic product ion at m/z 196 serves as a qualifying ion for
carboxylate species. This methodology has been successfully used in
conjunction with condensed phase membrane introduction mass spectrometry
(CP-MIMS), with barium acetate added directly to the methanol acceptor phase.
The combination enables rapid screening of carboxylic acids directly from
acidified water samples (wastewater effluent, spiked natural waters) using a
capillary hollow fibre PDMS membrane immersion probe. We have applied this
technique for the direct analysis of complex naphthenic acid mixtures spiked into
natural surface waters using CP-MIMS. Selectivity at the ionization and tandem
mass spectrometry level eliminate isobaric interferences from hydroxylated
species present within the samples, which have been observed in negative
electrospray ionization.
Description
Post-print
This is a pre-copyedited, author produced version of an article published as: Duncan, K.D., Volmer, D.A., Gill, C.G., & Krogh, E.T. (2016). Rapid screening of carboxylic acids from waste and surface waters by ESI-MS/MS using barium ion chemistry and on-line membrane sampling. Journal of the American Society for Mass Spectrometry, 27(3), 443-450. DOI: 10.1007/s13361-015-1311-y
This is a pre-copyedited, author produced version of an article published as: Duncan, K.D., Volmer, D.A., Gill, C.G., & Krogh, E.T. (2016). Rapid screening of carboxylic acids from waste and surface waters by ESI-MS/MS using barium ion chemistry and on-line membrane sampling. Journal of the American Society for Mass Spectrometry, 27(3), 443-450. DOI: 10.1007/s13361-015-1311-y