Desorption Electrospray Ionization (DESI)

A new method of desorption ionization is described and applied to the ionization of various compounds, including peptides and proteins present on metal, polymer, and mineral surfaces. Desorption electrospray ionization (DESI) is carried out by directing electrosprayed charged droplets and ions of solvent onto the surface to be analyzed. The resulting mass spectra are similar to normal ESI mass spectra in that they show mainly singly or multiply charged molecular ions of the analytes. Changes in the solution that is sprayed can be used to selectively ionize particular compounds, including those in biological matrices. In vivo analysis is demonstrated. Ambient mass spectrometry using desorption electrospray ionization (DESI): instrumentation, mechanisms and applications in forensics, chemistry, and biology Takats, Z.; Wiseman, J. M.; Cooks, R. G., J Mass Spectrom 2005, 40, (10), 1261-1275. Abstract: Analytical characteristics of DESI are summarized. Examples of applications to small and large molecules, to in situ analysis, and to high-throughput analyses are presented. Evidence is provided for both a heterogeneous charge-transfer mechanism and a droplet pick-up mechanism of ionization. The speed, lack of the need for sample preparation, selectivity, and sensitivity of DESI are all demonstrated and discussed. Instrumentation is also discussed. Forensic applications as well as emerging areas of application including tissue imaging are given emphasis. Analytical characteristics of DESI are summarized. Examples of applications to small and large molecules, to in situ analysis, and to high-throughput analyses are presented. Evidence is provided for both a heterogeneous charge-transfer mechanism and a droplet pick-up mechanism of ionization. The speed, lack of the need for sample preparation, selectivity, and sensitivity of DESI are all demonstrated and discussed. Instrumentation is also discussed. Forensic applications as well as emerging areas of application including tissue imaging are given emphasis. New approaches for quantitative analysis in biological fluids using mass spectrometric detection Hopfgartner, G.; Varesio, E.,. TRAC-Trend Anal Chem 2005, 24, (7), 583-589. Abstract Quantitative analysis with mass spectrometric detection is no longer limited to small molecules. A new focus of research is to understand biological processes at the molecular level and this requires more quantitative data for a large range of biomolecules, including low molecular weight compounds, peptides and proteins. Online approaches such as liquid chromatography (LC) mass spectrometry are restricted to atmospheric pressure ionization (API) in combination with LC while off-line approaches can be performed either with API or matrix-assisted laser desorption ionization (MALDI). Selected reaction monitoring quantitation remains the favorite modeQuantitative analysis with mass spectrometric detection is no longer limited to small molecules. A new focus of research is to understand biological processes at the molecular level and this requires more quantitative data for a large range of biomolecules, including low molecular weight compounds, peptides and proteins. Online approaches such as liquid chromatography (LC) mass spectrometry are restricted to atmospheric pressure ionization (API) in combination with LC while off-line approaches can be performed either with API or matrix-assisted laser desorption ionization (MALDI). Selected reaction monitoring quantitation remains the favorite mode