Fig. 2.

MS/MS annotations of two ceramides in negative ion mode of low energy CID: a ceramide [NS] (d18:1/26:0) and b ceramide [AS] (d18:1/16:0) as acetate adduct forms. The substructure ions were combinatorially assigned with hydrogen rearrangement (HR) rules (Table 1). Structures were depicted as the neutralized form, and the total count of rearranged hydrogens was assigned. The fragment ion arising from the internal rearrangement, which cannot yet be assigned by HR rules, is depicted in red