3D-O1-1050（3P-45） PDF
Investigation of MALDI plume composition by near-infrared femtosecond laser ionization and numerical simulation based on a semiequilibrium proton transfer model
A/M in the principal process MH++A ⇄M+AH+ has been approximated by the sample mixing ratio (A=analyte, M=matrix). In this study, we demonstrated that this approximation is valid even in the A/M mixing ratio range as high as 1 by using near-infrared femtosecond laser ionization mass spectrometry coupled with a standard MALDI source. The meaning of this result is that we can exclude the possibility that the well-known deviations of this model in the high A/M region are attributed to this approximation. In order to reproduce observed MALDI signal intensities in the high A/M region, we formulated a new model called a semiequilibrium model, in which parameter b representing extent of thermal equilibrium for the proton transfer reaction was added. Numerical simulation using this model successfully reproduced the variation of AH+/MH+ with optimized parameter sets {a≦10-5, b=0.95, and T=1200K} and {a≦10-5, b=0.98, T=1100K} for the Phe/DHB and Ala/DHB systems, respectively.