Use of particle beam liquid chromatography-electron impact mass spectrometry for structure elucidation of oxodipine and three of its metabolites.

In order to test the analytical capabilities of the particle beam liquid chromatograph-mass spectrometer interface in structural identification in drug metabolism, a liquid chromatographic-mass spectrometric (LC MS) method using this new technique was developed for oxodipine and some of its expected metabolites. After two extraction steps at pH 9 and 1.5, the separation of the compounds, which have a wide polarity range, was carried out by an isocratic high-performance liquid chromatographic method with a 25-cm cyano-bonded column. The compounds were eluted with hexane-methanol-methylene chloride (76:12:12). Mass spectra were recorded after electron impact ionization (75 eV) with a source temperature of 150 degrees C. Under these conditions, comparison of the spectra with those obtained after gas chromatography or with a direct introduction probe showed identical fragmentation patterns when a sufficient amount of product was injected for LC-MS analysis.