Ebrotidine and its metabolites studied by mass spectrometry with electrospray ionization. Comparison of tandem and in-source fragmentation

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.