MICRODIALYSIS INTRODUCTION HIGH-PERFORMANCE ANION-EXCHANGE CHROMATOGRAPHY IONSPRAY MASS-SPECTROMETRY FOR MONITORING OF ONLINE DESALTED CARBOHYDRATE HYDROLYSATES

A system for the determination of carbohydrates based on on-line micro dialysis introduction high-performance anion-exchange chromatography i ntegrated pulsed electrochemical detection/mass spectrometry (MS) usin g ionspray as the ionization technique, with on-line desalting, is pre sented. This coupling of techniques utilizes a cation-exchange membran e desalting device (CEMDD) which permitted the exchange of sodium ions with hydronium ions when sodium ion concentrations up to 600 mil were used to separate and elute oligosaccharides. The effective on-line de salting by the CEMDD of the effluent before its introduction into the mass spectrometer was achieved by the electrolysis of water with a 500 mA current. The use of the CEMDD in combination with ionspray elimina ted the need for a booster pomp and also the regenerating water improv ed the sensitivity in comparison with the use of sulphuric acid as oli gosaccharides could be detected down to 3 mu g ml(-1). The system was developed and used to monitor cationized oligosaccharides based on the ir singly [M + Na](+) and doubly sodiated [(M + 2Na)/2](2+) molecules during the hydrolysis of wheat starch. The MS/MS properties of maltose , trehalose and sucrose were used in combination with retention times to identify these disaccharides based on their dissociation patterns, which Pre characteristic of the type of glycosidic linkage. (C) 1998 b y John Wiley & Sons, Ltd.