Modified Glassy Carbon Electrode with Multiwall Carbon Nanotubes as a Voltammetric Sensor for Determination of Leucine in Biological and Pharmaceutical Samples

A simple and highly sensitive method is described for voltammetric determination of leucine in blood and urine samples; namely, a glassy carbon electrode with an effective method is modified with multiwall carbon nanotubes (MWNTs). The cyclic voltammetric results indicated that MWNTs remarkably enhanced electrocatalytic activity toward the oxidation of leucine. Under the optimum condition the calibration curve was linear in the concentration range 9.0 × 10−6 − 1.5 × 10−3 mol L−1, with the detection limit of 3.0 × 10−6 mol L−1 and a relative standard deviation (RSD%) lower than 3.0% (n = 5). Also, some kinetic parameters were determined and a multistep mechanism for oxidation of leucine was proposed.