Novel electrode reactions of diazepam, flunitrazepam and lorazepam and their exploitation in a new redox mode LC-DED assay for serum

摘要

Previously unreported voltammetric redox behaviour was identified for flunitrazepam, lorazepam and diazepam at a glassy carbon electrode. This was successfully exploited for their determination in serum by high performance liquid chromatography dual electrode detection in the redox mode (LC-DED). Initial studies were performed to optimise the chromatographic conditions and these were found to be 50% acetone, 50% 100 mM pH 2 phosphate buffer at a flow rate of 0.8 ml min~(-1), employing a Hypersil C_(18), 5 μm, 250 mm x 4.6 mm column held at 40 °C. Cyclic voltammetric studies were made to ascertain the redox behaviour of these benzodiazepines over the pH range 2-10. Hydrodynamic voltammetry was used to optimise the applied potential at the amperometric generator and detector cells; these were identified to be -2.45 V (vs. stainless steel) and +1.0 V. (vs. Ag/AgCl).