Microelectrode studies of isoflurane and oxygen vapour mixtures in dimethyl sulfoxide

The electrochemical reduction of the inhalation anaesthetic agent isoflurane was investigated at a commercially available Au microelectrode (5 μm) in DMSO solvent, individually, and also as a component of a simple vapour mixture with oxygen using both traditional voltammetric and potential step chronoamperometric techniques. 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. The observed cross-interference reaction is shown to be dependent of the electrode size and the concentration of the anaesthetic agent, isoflurane. Under steady-state conditions, and using small diameter microelectrodes (5 μm) and low isoflurane concentration ([ISO] <0.2% v/v), the superoxide/isoflurane reaction is shown to approach a one-electron process, where the coupled homogeneous reaction kinetics are almost "out-run". The use of potential step chronoamperometric techniques however, is shown to significantly reduce the deleterious cross-interference reaction between superoxide and isoflurane. In essence, this work provides scope for the development of a rapid, accurate and inexpensive electrochemical gas sensor for measuring anaesthetic vapour mixture under clinically relevant conditions. © 2004 Elsevier B.V. All rights reserved.