Mass spectrometric study of randomly methylated beta-cyclodextrins using ionspray, atmospheric pressure chemical ionization and matrix-assisted laserdesorption/ionization

Mixtures of methylated beta-cyclodextrins were characterized using three di fferent methods of mass spectrometry: ionspray, atmospheric pressure chemic al ionization (APCI) and matrix-assisted laser desorption/ionization (MALDI ), Each of these methods allows a fast and simple determination of the degr ee of substitution, and can provide evidence for differences in the methyla tion of batches which have very similar global degrees of substitution. The three methods are in good qualitative agreement, but there are systematic differences in the quantitative results for the percentages of the various methylated molecules present in a batch. This is attributed to ionization y ields which increase with the number of methyl groups, with different slope s for the different methods. Copyright (C) 2000 John Wiley & Sons, Ltd.