Infrared Matrix-Assisted Laser Desorption/Ionization Quadrupole Ion Trap Mass Spectrometry

Abstract

Performance characteristics of an infrared (IR) matrix-assisted laser desorption/ionization (MALDI) quadrupole ion trap (QIT) mass spectrometer are presented. Both an IR laser and an ultraviolet (UV) laser have been coupled to the MALDI ion source, allowing for a comparative study of the spectra obtained for the same analyte molecules taken at these two wavelengths. The mass range of the QIT instrument was extended by operating it at a frequency as low as 200 kHz. The results presented for small and medium-size peptides demonstrated a lesser degree of analyte ion fragmentation in the case of the IR-MALDI source compared with that obtained using the UV-MALDI source. Due to the fragmentation phenomenon, the mass resolution for cytochrome C ions(MW12384 Da) was an order of a magnitude higher in the case of IR-MALDI compared with the use of UV-MALDI. This phenomenon has been shown to effect the calibration of the trap instrument for higher masses.