Amperometric enzyme electrodes for xanthine determination with different mediators.

Two new amperometric carbon paste enzyme electrodes were developed for xanthine determination. 1,4-benzoquinone and poly(vinylferrocene) (PVF) were investigated as mediators. The parameters affecting the analytical performance of the enzyme electrode have been investigated in detail and optimized for modified enzyme electrodes. 1,4-benzoquinone modified enzyme electrode (BQ-CPEE) exhibited linear response from 1.9 × 10-7 M to 5.5 × 10-6 M and from 5.2 × 10-5 M to 8.2 × 10-4 M with a good detection limit of 1.0 × 10-7 M. The linear working range of the PVF modified enzyme electrode was between 1.9 × 10-7-2.1 × 10-6 M, 1.9 × 10-6-1.0 × 10-5 M and 1.1 × 10-4-8.8 × 10-4 M with a detection limit of 1.0 × 10-7 M. Hypoxanthine response of the electrodes was also determined. Modified enzyme electrodes were used for xanthine determination in real samples and good recoveries were obtained.