Comparative performances of a bare graphite-polyurethane composite electrode unmodified and modified with graphene and carbon nanotubes in the electrochemical determination of escitalopram

A bare composite graphite-polyurethane electrode (EGPU) and two other modified with graphene (EGPU-GR) and functionalized multi-walled carbon nanotubes (EGPU-CNTs) were prepared and compared regarding their voltammetric response to escitalopran (EST). The modifiers were characterized by Raman spectroscopy and the resulting electrode materials by contact angle measurements with a hydrophilicity character in the ascending order for the composites: GPU > GPU-GR > GPU-CNTs and scanning electron microscopy (SEM). The electroactive areas of the EGPU, EGPU-GR, and EGPU-CNTs were 0.065, 0.080, and 0.092 cm(2), respectively, calculated from the chronocoulometry using K-3[Fe(CN)(6)] as a probe and the Cottrell equation. The cyclic voltammograms obtained for EST indicated irreversible electrochemical behavior, with an anodic peak at cu. + 0.80 V (vs. SCE). These measurements were carried out with the three electrodes, and comparison of the analytical responses led to the EGPU-GR electrode being selected for use in the subsequent experiments. Under optimal conditions, square wave and differential pulse voltammetry at EGPU-GR presented linear dynamic ranges between 1.5 x 10(-6) and 1.2 x 10(-5) mol L-1, with a detection limit of 2.5 x 10(-7) mol L-1 (SWV) and 1.5 x 10(-6) and 1.2 x 10(-5) mol L-1, with a detection limit of 3.2 x 10(-7) mol L-1 (DPV) for EST. The proposed method was applied for the quantification of EST in synthetic urine and cerebrospinal fluid samples, offering advantages including simplicity of fabrication, no requirement for analyte preconcentration and surface renewal, fast response, and selectivity.