High-energy fragmentation of chlorophyll a and its fully deuterated analog by californium-252 plasma desorption mass spectrometry

Abstract

Comparison of the /sup 252/Cf=plasma distortion mass spectrometry (/sup 252/Cf-POMS) spectra of chlorophyll of ordinary isotopic composition((/sup 1/H)Chl a) with those of essentially fully deuterated Chl a ((/sup 2/H)Chl a) led to the establishment of the elemental compositions in the fragmentation pattern and to deduction of plausible structures for the fragment ions produced. The difference in mass between corresponding ions in the spectra gives the number of hydrogens in the molecule. It is necessary to assure that all ions contain 4 nitrogens in order to determine the elemental composition of any ion in question. The /sup 252/Cf-POMS spectra showed an intense molecular ion at 893.6+0.1..mu.., which corresponds to the isotopically averaged molecular weight of (/sup 1/H)Chl a, and 963.3+0.1..mu.., which corresponds to that of (/sup 2/H)Chl a. The mass difference confirms the expected extent of deuteration, 70 of the 72 H atoms in the (/sup 2/H)Chl a molecular ion are D. An intense partially resolved fragmentation pattern was observed from 300 to 700 ..mu... The pattern is mass shifted in the deuterated analog. Some explanation is offered for the fragmentation pattern. (BLM)