Negative ion tandem mass spectrometry of leukotriene E4 and LTE4 metabolites: Identification of LTE4 in human urine

The sulfidopeptide leukotrienes, leukotriene E 4, (LTE 4,) and its N-acetyl derivative and several ω- and β-oxidized metabolites of LTE 4, have been analyzed by tandem mass spectrometry. [M-H] - ions were produced by continuous flow fast atom bombardment, and collision-induced dissociation of these ions was studied by using a triple quadrupole instrument. The product ion spectra obtained were characteristic of the structure of LTE 4, and mechanisms of ion formation were investigated by using deuterated compounds. β-Elimination of the peptide portion of LTE 4, by loss of CO 2, and ethylene amine leaves the C-l carboxyl group ionized in the most abundant fragment ion for LTE 4, and all metabolites. Tandem mass spectrometry of fast atom bombardment-generated anions from ω- and β-oxidized metabolites of LTE 4, produced similar ions with only a minor influence of the third carboxyl group at the omega terminus evident. Tandem mass spectrometry was used to identify unequivocally the presence of unmodified LTE 4, in a high performance liquid chromatography-purified fraction of urine from a normal healthy volunteer after infusion with LTE 4.