Laser desorption-atmospheric pressure chemical ionization mass spectrometry for the analysis of peptides from aqueous solutions

Anal Chem. 2002 Nov 1;74(21):5600-5. doi: 10.1021/ac020402k.

Abstract

A recently reported ionization method, comprising an infrared (IR) laser pulse to desorb (LD) analyte species, followed by atmospheric pressure chemical ionization (APCI) with a corona discharge (LD-APCI) to effect ionization of the desorbed neutral analyte molecules, is described for the direct analysis of aqueous peptide solutions. The source employs a heated capillary atmospheric pressure (AP) inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. By use of the corona discharge, signals of the atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI)-generated analyte protonated molecule were enhanced by factors as large as 1400. In addition, the acid modifier trifluoroacetic acid (TFA) was found to improve the AP-IR-MALDI-generated signal by a factor of approximately 10, whereas the LD-APCI generated signal yielded a 100-fold increase. In this study, the use of the corona discharge is described to enhance the analyte signal generated via AP-IR-MALDI and, as a tool, to probe the gas-phase neutral molecule population generated by the MALDI process. Finally, through the decoupling of desorption from ionization, implications regarding the application of LD-APCI for the direct analysis of numerous new analyte containing matrixes (e.g., polyacrylamide gel electrophoresis (PAGE), tissue, etc.) are discussed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Peptides / analysis*
  • Sensitivity and Specificity
  • Spectrometry, Mass, Electrospray Ionization / instrumentation
  • Spectrometry, Mass, Electrospray Ionization / methods*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Trifluoroacetic Acid / pharmacology

Substances

  • Peptides
  • Trifluoroacetic Acid