Chemometric approach to evaluate the parameters affecting the determination of reaction rate constants by ion trap a lass spectrometry

The effects of experimental parameters on kinetic measurements performed with an ion trap mass spectrometer have been investigated by a chemometric approach using Experimental Design techniques. The selected experiment was the determination of the rate constant of the reaction CH3CO++CH3COCH3 --> CH3CO(H)CH3++CH2CO. In a first step, eight variables were studied: temperature, acetone pressure, buffer gas pressure, method of ion selection, ionization start mass, ionization time, mass range, and reaction time. The results show that isolation method and reaction time were the only parameters affecting rate constants determination, although temperature may be considered a "borderline" factor. The remaining parameters and their interactions do not significantly affect the kinetic measurements. A second series of runs was performed to check again the effect of reaction time, temperature, and ionization time in experiments with or without ion selection in order to compare the results of the present work with those obtained in a similar study on a Fourier transform-ion cyclotron resonance instrument. (C) 1998 American Society for Mass Spectrometry.