Ebrotidine and its metabolites studied by mass spectrometry with electrospray ionization. Comparison of tandem and...

Electrospray ionization was used for the analysis of ebrotidine and its potential metabolites. Since standard electrospray gave only the quasi-molecular ions for most of the compounds, two collision-induced dissociation (CID) experiments were carried out in order to obtain structural information: tandem mass spectrometry (MS/MS) and in-source fragmentation by increasing the cone voltage (CVF, cone voltage fragmentation). CVF produced more fragmentation than MS/MS, and the intensities of the fragments formed were also greater. Unlike Ms/MS spectra, CVF spectra gave ions which showed retention of the bromine isotope pattern, adducts with acetate and dehydration. The general fragmentation pathways observed for ebrotidine and its derivatives were basically the same for the CVF and MS/MS experiments. Most of the fragments were formed by the breaking of bonds to heteroatomics. In order to analyse biological samples containing ebrotidine and its biotransformation products, an HPLC/MS separation procedure with simultaneous UV detection was developed, allowing the identification of ebrotidine and its metabolites in human urine.