Identification of phosphonic acids by capillary electrophoresis-ionspray mass spectrometry.

The identification of alkylphosphonic acids in spiked tap water has been investigated by on-line capillary electrophoresis-UV spectrometry-mass spectrometry (CE-UV-MS) in negative-ion mode. The 5 mM sorbic acid-ammonia electrolyte (pH 6.5) allows simultaneous indirect UV and MS (ionspray) detection. Several parameters (electrolyte pH, make-up chemical composition and make-up flow-rate) have been optimized and 5 mg/l limit of detection has been reached for these analytes in selected ion monitoring MS detection. MS-MS detection has also been investigated to reach a low detection limit (100 micrograms/l) for alkyl alkylphosphonic acids in spiked tap water. The mass spectra of these compounds exhibit a very abundant negative ion, [M-H]- (MS) with characteristic fragmentation (MS-MS) of acids and monoesters. Quantitative analysis achieved with CE-UV shows good correlation coefficients and allows accurate quantification of the analytes.