Amperometric enzyme electrode for determination of theophylline in serum

✍ Scribed by Calum J. McNeil; Jonathan M. Cooper; Julia A. Spoors

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 541 KB
• Volume: 7
• Category: Article
• ISSN: 0956-5663
• DOI: 10.1016/0956-5663(92)85034-8

✦ Synopsis

This paper describes an amperometric enzyme electrode for the rapid determination of theophylline in serum. The method is based on the catalysed oxidation of theophylline by the haem-containing enzyme theophylline oxidase. Results are presented for two approaches. First, ferrocene monocarboxylic acid was used as a mediator. The second-order rate constant was 1.1 x 10(3) 1 mol-1 s-1. Secondly, the organic conducting salt NMP.TCNQ was used to construct enzyme electrodes. These electrodes were employed for the rapid (60 s) measurement of theophylline in serum at a working potential of +100 mV versus Ag/AgCl. Linear calibration curves were obtained over the clinically relevant range (y = 0.13x + 0.22, n = 8). Caffeine, theobromine and 3-methylxanthine at levels up to 100 mg l-1 do not interfere and 1-methylxanthine shows cross-reactivity at concentrations greater than 50 mg l-1.