COMPARISON OF TRIPLE QUADRUPOLE AND DOUBLE FOCUSING MASS SPECTROMETERS TO INVESTIGATE COLLISION-INDUCED DISSOCIATION AND METASTABLE IONS OFGLYCOCONJUGATES

Glycoconjugates, such as chromophore-labeled disaccharides and permeth ylated glycosphingolipids (GSL) were used for comparison of triple qua drupole and double focusing mass spectrometers in analysis of product ions. A profound effect of collision energy was observed in the produc t ion spectra of ceramide ions (fragment ions of permethylated GSL): m ore productions were observed from a double focusing mass spectrometer . Besides collision energy, the structure of the analyte had a signifi cant effect on the formation of product ions. Despite the fact that ma sses of protonated molecular ions (MH+) of permethylated GSL are signi ficantly larger than their ceramide fragments, the low-energy and high -energy product ion spectra of MH+ are, in general, similar. In a doub le focusing mass spectrometer of reversed geometry, more metastable io ns were observed in the first field free region (FFR) than in the seco nd FFR. The metastable ions observed in the second FFR were similar to those observed in low-energy collision-induced dissociation (CID). Al though a double focusing mass spectrometer is superior to triple quadr upole instrument for detection of product ions, the poor resolution in either the selection of precursor ion or in the product ion spectra c an be a serious problem in analysis of a mixture with similar masses.