Poly(4-vinylpyridine)-coated chemically modified electrode for the detection of uric acid in the presence of a high concentration of ascorbic acid

A poly(4-vinylpyridine)-coated carbon paste electrode (PVP/CPE) was developed for the selective determination of uric acid (UA) in the presence of ascorbic acid (AA) by square wave voltammetry. The oxidation of UA at carbon-based electrodes in acidic solutions suffers from interference from AA which can be oxidized at a potential close to that of UA. Due to the very distinct ability of AA and UA to form hydrogen bonds with PVP, the overlapped oxidation potentials of AA and UA can be separated. Linear calibration plots are obtained over the 0-9 mu M and 10-30 mu M in pH 1.1 buffer solution with slopes (mu A/mu M) and correlation coefficients of 3.6, 0.9992 and 7.5, 0.9989, respectively. The detection limit (3 sigma) is 0.2 mu M. The acceptable tolerance of concentration of AA for the determination of 20 mu M UA is at least as high as 0.1 mM. The practical analytical utility is illustrated by selective measurements of UA in human urine without any preliminary treatment.