title: 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.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Faculty of Applied Sciences, University of the West of England, Bristol, UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Howie
authors.forename: P
authors.initials: P
authors.lastname: Hawkins
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000295:instrumentation / Q000379:methods; D005336:Fiber Optic Technology; D005453:Fluorescence; D006221:Halothane / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006221:Halothane