Liquid Chromatography/Electrospray Ionization Tandem Mass Spectrometry and Derivatization for the Identification of Polar Carbonyl Disinfection By-Products

摘要

Derivatization with 2,4-dinitrophenylhydrazine (DNPH) in combination with LC-ESI/MS/MS was successfully applied to investigate polar disinfection by-products with carbonyl groups. The collision-induced dissociation mass spectra (CID-MS) show distinct fragments of the DNPH moiety which facilitates selective measurements of different carbonyl groups by tandem mass spectrometric experiments like precursor ion scans (e.g. m/z 163 for aldehydes; m/z 152 for ketones, m/z 182 for dicarbonyls and hydroxycarbonyls). Several multifunctional carbonyls could be tentatively identified in treated water samples by putting together all information of HPLC separation, derivatization, precursor ion scans, and CID-MS. However, DNPH derivatization is not a suitable reagent for halogenated carbonyl compounds due to side reactions. The chlorine is substituted by DNPH. O-(carboxymethyl) hydroxylamine (CMHA) is a suitable alternative. CMHA derivatization is specifically aimed at the carbonyl group and does not affect the chlorine. The formed oxime derivatives reveal abundant signal intensity in ESI and meaningful CID-MS with common fragments of the CMHA moiety and diagnostic fragments of the carbonyl moiety.