Microdialysis introduction high-performance anion-exchange chromatography/ionspray mass spectrometry for monitoring of on-line desalted carbohydrate hydrolysates

Abstract

A system for the determination of carbohydrates based on on-line microdialysis introduction high-performance anion-exchange chromatography integrated pulsed electrochemical detection/mass spectrometry (MS) using ionspray as the ionization technique, with on-line desalting, is presented. This coupling of techniques utilizes a cationexchange membrane desalting device (CEMDD) which permitted the exchange of sodium ions with hydronium ions when sodium ion concentrations up to 600 mM were used to separate and elute oligosaccharides. The e†ective on-line desalting 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 eliminated the need for a booster pump and also the regenerating water improved the sensitivity in comparison with the use of sulphuric acid as oligosaccharides could be detected down to 3 l gm lo1. The system was developed and used to monitor cationized oligosaccharides based on their singly [M + Na ]e and doubly sodiated [(M + 2Na)/2 ]2e 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 are characteristic of the type of glycosidic linkage. 1998 by John Wiley & Sons, Ltd.