Covalent modification of glassy carbon electrode with glutamic acid for simultaneous determination of uric acid and ascorbic acid

A novel covalently modified glassy carbon electrode with glutamic acid has been fabricated via an electrochemical oxidation procedure and was applied to the catalytic oxidation of uric acid (UA) and ascorbic acid (AA), reduci ng the overpotentials by about 0.2 V and 0.3 V, respectively. Based on its strong catalytic function toward the oxidation of UA and AA, the modified e lectrode resolved the overlapping voltammetric response of UA and AA into t wo well-defined voltammetric peaks with both cyclic voltammetry (CV) and di fferential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obt ained from DPV was linearly dependent on the UA and AA concentration in the range 2 x 10(-6)-4 x 10(-4) mol L-1 and 1.0 x 10(-6)-4 x 10(-4) mol L-1 wi th correlation coefficients of 0.996 and 0.997, respectively. The detection limits (3 delta) for UA and AA were 1.1 x 10(-6) mol L-1 and 9.2 x 10(-7) mol L-1, respectively. The modified electrode shows good sensitivity, selec tivity and stability, and has been applied to the determination of UA and A A simultaneously in human urine samples with satisfactory results.