Clustering and Nonclustering Modifier Mixtures in Differential Mobility Spectrometry for Multidimensional Liquid Chromatography Ion Mobility-Mass Spectrometry Analysis.

Modifiers provide fast and reliable tuning of separation in differential mobility spectrometry (DMS). DMS selectivity for separating isomeric molecules depends on the clustering modifier concentration, which is typically 1.5-3 mol % ratio of isopropanol or ethanol in nitrogen.

Improved metabolite characterization by liquid chromatography - Tandem mass spectrometry through electron impact type fragments from adduct ions.

Using a chimeric collision cell mounted on a quadrupole time-of-flight platform, collision induced dissociation (CID) and electron induced dissociation (EID) were investigated for the LC-MS analysis of low molecular weight compounds including drugs and endogenous metabolites. Compared to CID, EID fragmentation of the [M+H] species (10-20 eV) from standard compounds resulted in additional specific and informative fragments, mostly due to neutral losses and, in some cases due to ring openings. Some analytes, for example reserpine and vinpocetine, provided characteristic [M+H] species.

Automated parallel derivatization of metabolites with SWATH-MS data acquisition for qualitative and quantitative analysis.

For metabolite profiling chemical derivatization has been used to improve MS sensitivity and LC retention. However, for multi-analytes quantification, the number of commercially available isotopically labelled internal standards is limited. Besides, there is no single workflow which can provide large-scale metabolomics coverage in particular for polar metabolites.

Modifier Selectivity Effect on Differential Ion Mobility Resolution of Isomeric Drugs and Multidimensional Liquid Chromatography Ion Mobility Analysis.

Cluster formation in the alternating electric field during differential ion mobility is critical for separation selectivity and is governed by two factors. One is the reduced mass, and the other factor is cluster binding energy between an ion and a neutral solvent molecule (modifier). Therefore, separations of isomeric analytes using a modifier can be related to the thermochemistry of the cluster formation, as subtle changes in the molecular structure will affect its charge delocalization and the binding energy with the corresponding modifier will be different.