Determination of theophylline in tea and drug formulation using a Nafion (R)/lead-ruthenium oxide pyrochlore chemically modified electrode

Square-wave voltammetry was used for the determination of trace amounts of theophylline in tea and drug formulation at a Nafion(R)/lead-ruthenium oxid e pyrochlore chemically modified electrode. This chemically modified electr ode exhibits a marked enhancement of the current response compared to a bar e glassy carbon electrode. The calibration graph for the determination of t heophylline was linear up to 100 mu M in 0.1 M, pH 3 phosphate solution wit h a detection limit (S/N = 3) of 0.1 mu M. The results of 15 successive rep etitive measurement-regeneration cycles showed a relative standard deviatio n of 1.3% for 10 mu M theophylline indicating that the electrode renewal gi ves a good reproducible surface. Quantitative analysis was performed by the standard addition method for the theophylline content in commercially avai lable tea and drug. (C) 1999 Elsevier Science B.V. All rights reserved.