2P-10 PDF
Evaluation of Atmospheric Pressure Laser Desorption/Ionization at the Wavelength Range of 3 and 6 μm
Mid-infrared (IR) lasers within a wavelength range of 3 and 6 μm were compared to investigate suitable wavelength for ionization of peptide solution under atmospheric pressure (AP). Tunable lasers using optical parametric oscillation with a tunable range of 2.70–3.10 μm and difference-frequency generation with a tunable wavelength range of 5.50-10.00 μm were used. AP-IR-LDI ion source, replaced by ESI source of an ion trap mass spectrometer (LCQ classic, Thermo Finnigan, USA) was used to investigate the dependences of the signal intensity of protonated ion of the peptide on the wavelength and irradiated pulse energy at the 3 and 6 μm wavelength ranges. Angiotensin II was dissolved in the mixture solvent 80:20 in volume ratio of acetonitrile and water with 0.1% formic acid at a concentration of 10 pmol/μL. The highest ion signal intensity was observed at the wavelengths of 2.95 and 6.09 μm in the respective wavelength ranges. The peak intensity of [M + H]+ at 6.09 μm wavelength was comparable to that at 2.95 μm wavelength, when the pulse energy was 250 μJ. AP IR-LDI MS which employ the 6 μm-band laser can be used a novel way target at biomolecules such as in low or non-volatile solvent.