Influence of acceleration voltages on relative ion intensities in the post-source decay fragmentation of isomeric cyclic oligosaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Abstract

The isomeric sugar-branched cyclodextrin (CD) derivatives of 6-O-glucosyl-betaCD (G1-betaCD) and 6,6-di-O-glucosyl-alphaCD (G1, G1-alphaCD) were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry at the different acceleration voltages of 20 and 8 kV. In the post-source decay (PSD) fragment spectra of G1-betaCD and G1, G1-alphaCD under the reduced acceleration voltage 8 kV, the relative intensity ratios of one-site cleavage ions [M - G1](+) to two-site cleavage ions [M - G2 approximately 5](+) were much larger than at 20 kV. This change in the intensity ratio in the spectra of G1, G1-alphaCD was much larger than in the spectra of G1-betaCD. The measurements under the reduced acceleration voltage were useful to distinguish easily between the otherwise very similar PSD fragment spectra of G1-betaCD and G1, G1-alphaCD. It was concluded that the acceleration energy is one of the most effective parameters controlling relative ion intensities in PSD, and that distinction between these oligosaccharide isomers is facilitated by manipulation of this parameter.