Analysis of sulfobutyl ether-beta-cyclodextrin mixtures by ion-spray mass spectrometry and liquid chromatography-ion-spray mass spectrometry

The analysis of two commercial and two home-made sulfobutyl ether beta -cyc lodextrin (SBE-beta -CD) samples by ion-spray (IS) mass spectrometry and by liquid chromatography-mass spectrometry coupling (LC-MS) is investigated i n a negative ion mode. SBE-beta -CD fragmentation was first investigated by direct infusion. In IS, the best conditions for SBE-beta -CD ionization co nsisted of ammonium acetate added to an acetonitrile/water mixture as sampl e solvent. These conditions allowed simplification of the mass spectrum, ma inly by the formation of dicharged species [M-2H](2-), thus limiting the pr oduction of multicharged fragments. IS-MS permits fast and simple measureme nt of the substitution pattern and determination of the global degree of su bstitution for SBE-beta -CD mixtures. A complementary method using LC-MS wa s developed for the analysis of these mixtures. The substitution patterns o btained by LC-MS are in good agreement with those determined by direct MS a nalysis. The LC-MS coupling enabled separation of the mixtures versus the c harge in anion-exchange chromatography (AEC) whereas no separation of the d ifferent substitution isomers potentially present in the SBE-beta -CD mixtu re was displayed. The AEC methodology described can be successfully used fo r fractionation of SBE-beta -CD derivatives at the semi-preparative scale. (C) 2001 Elsevier Science B.V. All rights reserved.