3C-O2-1635（3P-46） PDF
Investigation of the Pressure of the Infrared Laser Ionization Source for Improvement of LC/MS Sensitivity for Membrane Proteins
Infrared (IR) laser ionization has been expected as a breakthrough of rapid mass spectrometry of membrane proteins for its tolerance to detergents or buffer salts, and development of sample introduction methods has been needed for the purpose of application to online LC/MS. In this study, an ESI source of a Q-TOF differential pumping mass spectrometer was modified to a continuous flow IR laser ionization source using a frit made with stainless steel, and online LC/MS was successfully performed under atmospheric pressure. However, the problem of low ion transfer efficiency from atmospheric pressure into the vacuum of the mass spectrometer had remained. To improve the ion transfer efficiency, we constructed a vacuum chamber covering the ion source, and IR laser ionization at a reduced pressure was examined. As a result, ion signal intensity of IR laser ionization was 3.8 times increased by reducing pressure from 101 kPa to 71 kPa. In the future work, the online LC/MS of a digest of membrane proteins which is difficult to be analyzed with ESI will be challenged.