title: Enhancing Performance of Liquid Sample Desorption Electrospray Ionization Mass Spectrometry Using Trap and Capillary Columns.
abstract: Desorption electrospray ionization mass spectrometry (DESI-MS) is a recent and important advance in the field that has extensive applications in surface analysis of solid samples but has also been extended to analysis of liquid samples. The liquid sample DESI typically employs a piece of fused silica capillary to transfer liquid sample for ionization. In this study, we present the improvement of liquid sample DESI-MS by replacing the sample transfer silica capillary with a trap column filled with chromatographic stationary phase materials (e.g., C4, C18). This type of trap column/liquid sample DESI can be used for trace analysis of organics and biomolecules such as proteins/peptides (in nM concentration) in high salt content matrices. Furthermore, when the sample transfer capillary is modified with enzyme covalently bound on its inside capillary wall, fast digestion (< 6 min) of proteins such as phosphoproteins can be achieved and the online digested proteins can be directly ionized using DESI with high sensitivity. The latter is ascribed to the freedom to select favorable spray solvent for the DESI analysis. Our data shows that liquid sample DESI-MS with a modified sample transfer capillary has significantly expanded its utility in bioanalysis.
authors.affiliation: Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH, 45701, USA.
authors.forename: Si
authors.initials: S
authors.lastname: Cheng
authors.affiliation: Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH, 45701, USA ; Department of forensic science, Jiangsu Police Institute, Nanjing, Jiang Su, 210031, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH, 45701, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Cai
authors.affiliation: Department of Chemistry and Biochemistry, Department of Biological Chemistry, David Geffen School of Medicine at UCLA, and UCLA/DOE Institute for Genomics and Proteomics, University of California-Los Angeles, Los Angeles, California 90095, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Loo
authors.affiliation: Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH, 45701, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
keywords: Mass spectrometry; desalting and enrichment; desorption electrospray ionization; online enzyme digestion; phosphoprotein