Evaluation of quadrupole time-of-flight tandem mass spectrometry and ion-trap multiple-stage mass spectrometry for the differentiation of C-glycosidic flavonoid isomers.

LC-MS-MS is becoming a very important tool for the on-line identification of natural products in crude plant extracts. For an efficient use of this technique in the dereplication of natural products, a careful study of the parameters used to generate informative MS-MS spectra is needed. In this paper, the collision-induced dissociation (CID) MS-MS spectra of ubiquitous C-glycosidic flavonoids have been systematically studied using hybrid quadrupole time-of-flight and ion-trap (IT) mass analysers under various CID energy conditions. Efficient differentiation of flavonoid C-glycoside isomers was possible, based on the comparison of CID-MS-MS spectra of particular C-glycoside unit fragments. Striking differences between 6-C and 8-C flavonoid glycosides were especially observed in the product ion spectra of their 0.2X+ fragments ([M+H-120]+). Some guidelines for the on-line characterisation of C-glycosidic flavonoids by LC-MS-MS or LC-multiple-stage MS are given.

Analysis of a standard peptide mixture by capillary electrophoresis with mass spectrometry and with tandem mass spectrometry.

The combination of capillary electrophoresis with mass spectrometry allows efficient separation and identification of components in mixtures with greater specificity than can be obtained using capillary electrophoresis and ultra violet detection alone. For the mixture of peptides analysed in this application, molecular mass information was obtained on all of the components in the initial analysis. On-line capillary electrophoresis/tandem mass spectrometry was then used to generate amino acid sequence information for each of these peptides, at the pmole level, in the form of collision-induced production-ion spectra which were recorded only over the relevant time windows.