AVS 53rd International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS+BI-WeA

Invited Paper AS+BI-WeA5
Desorption Electrospray Ionization: Fundamentals and Applications in Surface Analysis and Biological Imaging

Wednesday, November 15, 2006, 3:20 pm, Room 2005

Session: Imaging and Characterization of Biological Materials
Presenter: R.G. Cooks, Purdue University
Authors: R.G. Cooks, Purdue University
Z. Takats, Purdue University
J.M. Wiseman, Purdue University
D. Ifa, Purdue University
N. Talaty, Purdue University
A. Jackson, Purdue University
A. Venter, Purdue University
Correspondent: Click to Email
This talk concerns ambient ionization using desorption electrospray ionization (DESI) and the related methods. These procedures allow direct analysis of biological samples, including proteins and lipids, on surfaces or in tissue without sample preparation. Biological fluids can also be examined directly, or by adsorption on a matrix like paper. DESI is suitable for characterization of both large and small molecules and it combines features of electrospray ionization (ESI) with those of the family of desorption ionization (DI) methods. It allows organic molecules present on surfaces to be analyzed by mass spectrometry without requiring that the sample be introduced into the vacuum system of the mass spectrometer. DESI has high sensitivity, is virtually instantaneous in response time, and there is little or no sample preparation. The sample is sprayed with charged microdroplets of water or a simple organic solvent. The sample remains fully accessible to observation as well as additional physical and chemical processing during the analysis. Applications to metabolomics, to high throughput analysis of pharmaceutical preparations, to drugs and drug metabolites in blood, serum and other biological fluids, are described. Tissue imaging is demonstrated with lipids being used as biomarkers to search for disease and in-vivo sampling of living tissue surfaces is described. Laser doppler anemometry is used to characterize the DESI mechanism. It is shown that at least two major processes are involved. One involves transfer of molecules from the surface to the droplet projectiles, the other involves proton or other charge transfer from the slow-moving projectile to the sample molecule. Variations on the DESI method in which reactive compounds are included in the spray solvent allow recognition of specific functional groups.