Desorption Electrospray: A Modern Tool for Organic Surface Analysis

Abstract

Applicability of mass spectrometry is related to the progress in instrumentation including ion sources. Ionization techniques in MS often need sample preparation, which increases the analysis time. From this point of view, DESI (desorption electrospray ionization) seems to be an interesting alternative. Electrospraying of a sample with a liquid leads to the production of analyte ions desorbed from the surface-deposited sample. A new modification of DESI, where electrospraying is provided by nano-ESI, and a new application in chiral analysis have been developed. Chiral analysis employs the Cooks kinetic method. Chiral selector is sprayed by nano-ESI onto the surface with a deposited chiral analyte. Trimeric clusters are formed in the bulk of the ion source. Their fragmentation allows chiral discrimination of enantiomers. The power of the DESI-based mass spectrometric tool is demonstrated on chiral analysis of ephedrine in commercial pharmaceutical Mucoseptonex^® E. The analysis is performed without any sample preparation. That is why the analysis is simple and cost-effective. Calibration for ephedrine was performed with D-enantiomer and the racemate (correlation coefficient R² = 0.996) was obtained.