title: Novel reductive-reductive mode electrochemical detection of Rohypnol following liquid chromatography and its determination in coffee.
abstract: Rohypnol (flunitrazepam) has been successfully determined in coffee by high performance liquid chromatography dual electrode detection (LC-DED) in the dual reductive mode. Initial studies were performed to optimise the chromatographic conditions and these were found to be 50% acetonitrile, 50% 50 mM pH 2.0 phosphate buffer at a flow rate of 0.75 mL min(-1), employing a Hypersil C18, 5 μm, 250 mm × 4.6 mm column. Cyclic voltammetric studies were made to ascertain the redox behaviour of Rohypnol at a glassy carbon electrode over the pH range 2-12. Hydrodynamic voltammetry was used to optimise the applied potential at the generator and detector cells; these were identified to be -2.4 V and +0.8 V for the redox mode and -2.4 V and -0.1 V for the dual reductive mode respectively. A linear range of 0.5-100 μg mL(-1), with a detection limit of 20 ng mL(-1) was obtained for the dual reductive mode. Further studies were then performed to identify the optimum conditions required for the LC-DED determination of Rohypnol in beverage samples. A convenient and rapid method for the determination of Rohypnol in beverage samples was developed using a simple sample pre-treatment procedure. A recovery of 95.5% was achieved for a sample of white coffee fortified at 9.6 μg mL(-1) Rohypnol.
authors.affiliation: Centre for Research in Bioscience, Department of Biological, Biomedical and Analytical Sciences, University of the West of England, Bristol, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Honeychurch
authors.affiliation: Centre for Research in Bioscience, Department of Biological, Biomedical and Analytical Sciences, University of the West of England, Bristol, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Gwen M
authors.initials: GM
authors.lastname: Davidson
authors.affiliation: Centre for Research in Bioscience, Department of Biological, Biomedical and Analytical Sciences, University of the West of England, Bristol, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Brown
authors.affiliation: Centre for Research in Bioscience, Department of Biological, Biomedical and Analytical Sciences, University of the West of England, Bristol, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK. Electronic address: john.hart@uwe.ac.uk.
authors.forename: John P
authors.initials: JP
authors.lastname: Hart
mesh_terms: D001628:Beverages / Q000032:analysis; D002244:Carbon / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003069:Coffee / Q000737:chemistry*; D055664:Electrochemical Techniques; D004566:Electrodes; D005445:Flunitrazepam / Q000032:analysis* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction
chemical_list: D003069:Coffee; D005445:Flunitrazepam; D002244:Carbon
keywords: Beverages; Cyclic voltammetry; Drug facilitated assault; Liquid chromatography dual electrode detection; Rohypnol