Preparation of selective and sensitive electrochemically treated pencil graphite electrodes for the determination of uric acid in urine and blood serum

In this study, the preparation of electrochemically treated pencil graphite (ETPG) electrodes in the mixture of lithium perchlorate and sodium carbonate solutions was investigated for the first time in the literature. The prepared ETPG electrodes showed high selectivity and sensitivity for uric acid (UA) oxidation over ascorbic acid and dopamine. Differential pulse voltammetry (DPV) was used as electrochemical method. The parameters affecting the UA oxidation were investigated. The optimal pH for UA oxidation was determined as 2. The adsorption of UA on ETPG surface reached saturation in 180 s. The oxidation peak current values versus UA concentration at the ETPG electrode showed linearity in the range from 0.05 mu M to 10.0 mu M (R-2 = 0.9962) with a detection limit of 1.5 nM (S/N=3). The oxidation peak of UA on the EITG electrode did not show any significant change in the presence of certain interferents except bovine serum albumin. The prepared electrodes showed good fabrication reproducibility. The analytical applications of the prepared electrodes were tested by using human urine and blood serum samples. The recovery results of different amounts of UA in urine were varied between 98.6% and 106.4% implying no matrix effect. It was observed that the standard addition method was more satisfactory in the case of blood serum samples. (C) 2010 Elsevier B.V. All rights reserved.