Application of a modified graphene nanosheet paste electrode for voltammetric determination of methyldopa in urine and pharmaceutical formulation

Electrochemical sensors and biosensors for pharmaceutical, food, agricultural and environmental analyses have been growing rapidly due to electrochemical behavior of drugs and biomolecules and partly due to advances in electrochemical measuring systems. In the present work, we describe the preparation of a new electrode composed of graphen (G) modified with 2,7-bis(ferrocenyl ethyl) fluoren-9-one (2,7-BFGPE) and investigate its performance for the electrocatalytic determination of methyldopa in aqueous solutions. Experimental section was carried out using cyclic voltammetry, square wave voltammetry and chronoamperometry. Under the optimized conditions (pH 7.0), the square wave voltammetric peak current of methyldopa increased linearly with methyldopa concentration in the ranges of 9.0 × 10−8 to 5.0 × 10−4 M. The detection limit was 5.0 × 10−8 M methyldopa. The diffusion coefficient (D= 9.35 × 10−6 cm2/s) and electron transfer coefficient (α=0.52) for methyldopa oxidation were also determined. The method shows the development of a sensor for selective and sensitive determination of methyldopa. This sensor was successfully applied to determine the methyldopa in some real samples.