Table 2.

m/z of the molecular species, fatty acid losses, elemental compositions, and accuracy values that occur during MS fragmentation of each mass in lipid groups III, II, and I^a

^aR2-COOH and R1-CH=C=C=O losses result from fragmentation to fatty acid (FA) and βOH-FA, respectively, in the structure shown. TMO, R3 = R4 = R5 = CH₃; DMO, R3 = R4 = CH₃, R5 = H; MMO, R3 = CH₃, R4 = R5 = H.

^bGroup III, M⁺; groups I and II, [M+H]⁺.

^cRel. abun., relative abundance, i.e., the peak area percentage of each lipid within its respective group.

^dIn general the 0.5-Δ mmu (milli-mass unit) range was used as a measure of very high-confidence molecular formula assignments, and the 1.0-Δ mmu range was used as a measure of good-confidence molecular formula assignments (63–65).