Issue 1, 1993

Fast-responding, fibre-optic based sensing system for the volatile anaesthetic halothane, using an ultraviolet absorption technique and a fluorescent film

Abstract

An improved version of a fast-responding sensing system for the widely used volatile anaesthetic halothane (2-bromo-2-iodo-1,1,1-trifluoroethane) is described. The concentration of halothane is determined using an ultraviolet radiation (UV) absorption technique. Ultraviolet radiation at 230 nm is conveyed by a silica optical fibre to a gas flow-through cell containing the halothane, and the intensity of the UV reaching the other side of the cell is measured using a fluorescent polymer film. This paper describes the development of an efficient fluorescent polymer film for the sensor based on poly(ethylene glycol) containing two fluorophores {2,5-diphenyloxazole and tris[4,4,4-trifluoro-1-(2-thienyl)butane-1,3-diono]europium(III)}. The film fluoresces strongly with a red line spectrum when excited in the range from about 200 to 380 nm. There is evidence of direct energy transfer between the two fluorophores. A similar effect is observed in films prepared from Carbowax 20M and the europium chelate. An advantage of this approach is that the fluorescent radiation can be transmitted back to a silicon photo-detector using an inexpensive polymer optical fibre bundle. Two experimental sensor systems for halothane are described and the results show that, although the response does not obey the Beer–Lambert law, a reliable system for determining halothane can be constructed, which operates over the medically important range 0–3%. This paper also describes how the signal-to-noise ratio of the system can be improved by using the long fluorescence lifetime of the film. A system for relaying the fluorescent radiation efficiently to polymer optical fibres is described, which is based on a clear film of poly(methyl methacrylate) containing the two fluorophores. The sensor head is compact and has a fast response time, thereby making it suitable for end-tidal respiratory gas measurements. The sensing system could also be used with other gases or liquids that absorb in the range 200–380 nm.

Article information

Article type
Paper

Analyst, 1993,118, 35-40

Fast-responding, fibre-optic based sensing system for the volatile anaesthetic halothane, using an ultraviolet absorption technique and a fluorescent film

J. A. B. Howie and P. Hawkins, Analyst, 1993, 118, 35 DOI: 10.1039/AN9931800035

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