Amperometric enzyme electrode for determination of theophylline in serum.
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.
McNeil
C J
CJ
Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK.
Cooper
J M
JM
Spoors
J A
JA
D015374:Biosensing Techniques; D004553:Electric Conductivity; D004800:Enzymes, Immobilized; D005296:Ferrous Compounds / Q000737:chemistry*; D007700:Kinetics; D000075163:Metallocenes; D008991:Monitoring, Physiologic / Q000379:methods*; D009942:Organometallic Compounds / Q000737:chemistry*; D013806:Theophylline / Q000097:blood*; D013997:Time Factors
D004800:Enzymes, Immobilized; D005296:Ferrous Compounds; D000075163:Metallocenes; D009942:Organometallic Compounds; D013806:Theophylline; C004998:ferrocene