Selective determination of L-tyrosine in the presence of ascorbic and uric acids at physiological pH using the electropolymerized film of 3-amino-5-mercapto-1,2,4-triazole

The selective determination of L-tyrosine (Tyr) in the presence of important interferents, ascorbic acid (AA) and uric acid (UA) at physiological pH in phosphate buffer solution was reported for the first time using the electropolymerized film of 3-amino-5-mercapto-1,2,4-triazole on glassy carbon electrode (p-AMTa electrode). Bare glassy carbon (GC) electrode fails to resolve the voltammetric signal of Tyr in the presence of AA and UA due to the surface fouling caused by the oxidized products of AA and UA. However, the p-AMTa electrode not only separates the voltammetric signals of AA, UA and Tyr with potential differences of 200 and 340 mV between AA-UA and UA-Tyr, respectively but also shows higher oxidation currents for these analytes. The p-AMTa electrode shows better selectivity toward Tyr in the presence of higher concentrations of AA and UA. The amperometric current response was increased linearly with increasing Tyr concentration in the range of 5.0 x 10(-8)-1.0 x 10(-4) M and the limit of detection (LOD) was found to be 1.9 x 10(-10) M (S/N = 3). The practical application of the present modified electrode was successfully demonstrated by measuring Tyr in human urine samples. (C) 2011 Elsevier B.V. All rights reserved.