title: Amperometric enzyme electrode for theophylline.
abstract: An amperometric biosensor for theophylline, based on the recently isolated enzyme theophylline oxidase, is described. The enzyme is entrapped, together with a ferricytochrome C cofactor, within a polymeric (Nafion) coating. The anodic detection (at +0.4 V versus Ag-AgCl) is facilitated by the addition of a redox-mediating hexacyanoferrate(III) ion. The influence of various experimental variables is described. The limit of detection is 2 x 10(-6) mol dm-3 theophylline, with linearity prevailing up to 3 x 10(-4) mol dm-3. The fast response and wash times permit rapid flow-injection measurements, with a frequency of 180 samples h-1 and a relative standard deviation of 3.0-4.0%. Prospects of using this electrode for clinical diagnostics are discussed.
authors.affiliation: Department of Chemistry, New Mexico State University, Las Cruces 88003.
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: E
authors.initials: E
authors.lastname: Dempsey
authors.forename: M
authors.initials: M
authors.lastname: Ozsoz
authors.forename: M R
authors.initials: MR
authors.lastname: Smyth
mesh_terms: D015374:Biosensing Techniques; D004563:Electrochemistry / Q000379:methods; D004566:Electrodes; D010088:Oxidoreductases; D013806:Theophylline / Q000032:analysis*
chemical_list: D013806:Theophylline; D010088:Oxidoreductases; C073406:theophylline oxidase