Adsorption and determination of sibutramine in illegal slimming product using porous graphene ink-modified electrode

This work presents a new material, i.e., a porous graphene ink to modify on the GCE surface (PGr-ink/GCE) to improve sensitivity by increasing the surface area of the electrode for the electrochemical determination of sibutramine. The surface characterization and electrochemical adsorption behavior of the PGr-ink/GCE toward sibutramine were investigated using scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ATR-FTIR spectroscopy and square wave adsorptive stripping voltammetry (SWAdSV). The PGr-ink/GCE exhibited a distinctive anodic response towards sibutramine using SWAdSV in BR buffer (pH 8.00) with a sensitivity 4 times higher than the bare GCE. Under the optimum conditions, the modified electrode showed good electrochemical adsorption and detection of sibutramine by the SWAdSV method with two ranges of linear concentration from 0.015 to 10.0 μg mL^-1 and 10-50 μg mL^-1. The limit of detection and quantitation were 5 ng mL^-1 and 15 ng mL^-1, respectively. Over a short analysis time (180 s), the sensor exhibited high sensitivity (10.9 μAμg^-1mLcm^-2), good reproducibility (RSD <3.4% n = 6), repeatability (RSD between 1.8 and 9.8% (n = 15)), excellent anti-interference properties and was successfully applied for the quantification of sibutramine in different brands of illegal slimming products with good recoveries (93 ± 4-104 ± 1%). The developed electrochemical sibutramine sensor is suitable for application in detecting illegal components in slimming products.