Transmission Mode Desorption Electrospray Ionization

A new mode of operation for desorption electrospray ionization (DESI) analysis of liquids or solid residues from evaporated solvents is presented. Unlike traditional DESI, the electrospray is not deflected off of a surface but instead is transmitted through a sampling mesh at a 0 degrees angle between the electrospray tip, sample mesh, and capillary inlet of a mass spectrometer. In this configuration, deposited samples can be analyzed rapidly without rigorous optimization of spray distances or angles and without the preparation time associated with solvent evaporation. The new transmission mode desorption electrospray ionization (TM-DESI) technique is not applicable to bulk materials, but instead is a method designed to simplify the sample preparation process for liquid samples and sample extracts. The technique can reduce analysis time to seconds while consuming only microliters of sample. The results presented summarize the optimization of the technique, highlight key figures of merit for several model compounds, and illustrate potential applications to high throughput screening of liquid mixtures in both extraction solvents and biological matrices. (J Am Soc Mass Spectrom 2008, 19, 1612-1620) (C) 2008 American Society for Mass Spectrometry