Elimination of the concentration dependence in mass isotopomer abundance mass spectrometry of methyl palmitate using metastable atom bombardment.

摘要: An important problem in mass isotopomer abundance spectrometry (MIAMS) is the dependence of measured abundances on sample concentration. We have evaluated role ionization energy ratios methyl palmitate as a function Ionization was varied using electron impact (EI) and metastable atom bombardment (MAB). The latter generates beam species capable ionizing analyte molecules by Penning ionization. observed that EI (70 eV) showed greatest molecular ion fragmentation also relative 3P2 3P0 states krypton (9.92 10.56 eV, respectively) resulted almost no fragmentation, quantified were essentially independent argon (11.55 11.72 intermediate between MAB(Kr) an concentration which less severe than with but more MAB(Kr). decrease consistent hypothesis proton transfer from fragment cation to neutral molecule gas phase reaction mechanism responsible for dependence. Alternative explanations, e.g., hydrogen abstraction cation, not supported these results. Moreover, MAB technique shows potential eliminating one source error MIAMS measurements palmitate, particular, fatty acids esters, general.