Electrochemical studies of the anaesthetic agent isoflurane (1-chloro-2,2,2-trifluoroethyl difluoromethyl ether) in binary gas mixtures with oxygen and nitrous oxide

Abstract

The electrochemical reduction of the inhalation anaesthetic agent isoflurane was investigated at a variety of microelectrode substrates (Au, Ag and Cu) in DMSO solvent, individually, and also as a component of a simple binary gas mixture with oxygen or nitrous oxide. In a binary gas mixture with oxygen, isoflurane is shown to react with the superoxide anion radical, formed from the electro-reduction of oxygen complicating their simultaneous detection. However, the electro-reduction of oxygen is shown to be dependent of the electrode size and the concentration of the anaesthetic agent, isoflurane. Using microelectrodes with diameters ≤5 μm and low isoflurane concentration ([ISO]<0.2% (v/v)), the reduction is shown to be a one-electron process, since the homogeneous reaction kinetics are essentially “out-run”. Using larger microelectrodes (diameters≥10 μm), or with higher concentrations of isoflurane, (0.5>[ISO]<2.0% (v/v)) the reduction current is augmented by the catalytic regeneration of oxygen, formed by the reaction between superoxide and isoflurane. By contrast, in a binary gas mixture with nitrous oxide, isoflurane reduction is shown to be unaffected by nitrous oxide or it is reduction products. The reduction waves for isoflurane and nitrous oxide are concomitant which complicates their simultaneous detection somewhat. In essence, this work provides scope for the development of a rapid, accurate and inexpensive electrochemical gas sensor for measuring the concentration of anaesthetic agents during surgery.