PUB - Publikationen an der Universität Bielefeld

Long-chain ferulic acid esters, such as eicosyl ferulate (1), show a complex and analytically valuable fragmentation behavior under negative ion electrospay collision-induced dissociation ((-)-ESI-CID) mass spectrometry, as studied by use of a high-resolution (Orbitrap) mass spectrometer. In a strong contrast to the very simple fragmentation of the [M + H](+) ion, which is discussed briefly, the deprotonated molecule, [M - H](-), exhibits a rich secondary fragmentation chemistry. It first loses a methyl radical (MS2) and the ortho-quinoid [M - H - Me](-center dot) radical anion thus formed then dissociates by loss of an extended series of neutral radicals, CnH2n + 1 center dot (n = 0-16) from the long alkyl chain, in competition with the expulsion of CO and CO2 (MS3). The further fragmentation (MS4) of the [M - H - Me - C3H7](-) ion, discussed as an example, and the highly specific losses of alkyl radicals from the [M - H - Me - CO](-center dot) and [M - H - Me - CO2](-center dot) ions provide some mechanistic and structural insights.