Field desorption mass spectrometry of phospholipids. II—fragmentation of dipalmitoylphosphatidyl choline from comparison ofd0,d4 andd9 species

Abstract

Field desorption mass spectra have been obtained for dipalmitoylphosphatidyl choline-d₀, -d₄ and -d₉. The two latter compounds were synthesized from dimethylene-d₄ choline bromide and trimethyl-d₉ choline bromide, respectively. Comparison was made of spectra of these three compounds obtained at different field anode temperatures in order to establish the composition of the major cleavage, rearrangement, and association ions. At low anode heating currents (≤ 20 mA) the most intense peak is [M + 1]⁺ which accounts for c. one-third of the total ionization. At higher temperatures various fragmentation processes, some of which are without analogy in electron impact mass spectrometry, become more important. The presence of an intermolecular methyl transfer process has been confirmed.