Electrochemical reduction of the anaesthetic agent sevoflurane (fluoromethyl 2,2,2-trifluoro-1-[trifluoromethyl] ethyl ether) in the presence of oxygen and nitrous oxide

Abstract

The electrochemical reduction of the inhalation anaesthetic agent sevoflurane was investigated at a variety of microelectrode substrates (Au, Ag and Cu) in dimethyl sulphoxide (DMSO) solvent, individually, and also as a component of a simple tertiary gas mixture with oxygen and nitrous oxide. In a gas mixture with oxygen, sevoflurane is shown to react with the superoxide anion radical, formed from the electro-reduction of oxygen complicating their simultaneous detection. However, the apparent timescale of reaction between the electrochemically produced superoxide and sevoflurane is shown to be dependent of the electrode size and the concentration of the anaesthetic agent, sevoflurane. Using microelectrodes with diameters ≤5 μm and low sevoflurane concentration ([SEVO]<0.2%, v/v), the reduction is shown to be a one-electron process, the superoxide/sevoflurane reaction kinetics are essentially “out run”. Using larger microelectrodes (diameters≥10 μm), or with higher concentrations of sevoflurane (0.5<[SEVO]<2.0%, v/v) the reduction current is augmented by the catalytic regeneration of oxygen, formed by the reaction between superoxide and sevoflurane. By contrast, in a tertiary gas mixture with nitrous oxide, sevoflurane reduction is shown to be unaffected by nitrous oxide or its reduction products. Unlike other anaesthetic agents, the reduction wave for sevoflurane no longer lies concomitant with the reduction wave of nitrous oxide. This work is a continuation of the development towards a rapid, accurate and inexpensive electrochemical gas sensor for the delivery of anaesthetic agents during surgery.