単糖およびオリゴ糖の配位子交換モードによる液体クロマトグラフィー／質量分析法

Abstract

A technique was developed for ligand-exchange liquid chromatography/mass spectrometry (LC/MS) of mono- and oligosaccharides. A mixture of seven monosaccharides, four disaccharides, and two trisaccharides was successfully analyzed by using an improved ligand-exchange column comprising a semi-rigid styrene-divinylbenzene copolymer-based Ca-type cation-exchange resin (ULTRON PS-80C/10S) in conjunction with electrospray-ionization mass spectrometry (ESI-MS). Water was used as a mobile phase to separate the saccharides within 12 min. The ESI interface was used in negative-ion mode for LC/MS and produced reasonable signals from negative molecular ions ([M-H]-) of the saccharides. The effect of aqueous ammonia used as an additive in the eluent was also examined. The detection sensitivities of the saccharides increased when aqueous ammonia was used as an additive at a concentration of 2 vol%. The effects of separation and ionization parameters, column temperature, and cone voltage on the sensitivity and linearity were examined. Linear plots of peak area versus concentration were obtained for MS detection over the range 5-1000 μM (r2=0.951-0.999) for each saccharide. The detection limits of the target saccharides calculated at a signal-to-noise ratio of 3 ranged from 3.7 to 17.1 ng. The reproducibility of the retention times was 0.66-1.2% and that of the peak areas was 0.96-2.86%. A comparison of these results with those obtained with a normal-phase semimicro aminopropyl column confirmed the usefulness of ligand-exchange LC/MS of mono- and oligosaccharides. The newly developed method was applied in the determination of mono- and oligosaccharides extracted from seaweed and hydrolyzed by a hydrothermal reaction.