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 x 10(-7) M to 5.5 x 10(-6) M and from 5.2 x 10(-5) M to 8.2 x 10(-4) M with a good detection limit of 1.0 x 10(-7) M. The linear working range of the PVF modified enzyme electrode was between 1.9 x 10(-7)-2.1 x 10(-6) M, 1.9 x 10(-6)-1.0 x 10(-5) M and 1.1 x 10(-4)-8.8 x 10(-4) M with a detection limit of 1.0 x 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.