Voltametric Determination of Dopamine in Urine Samples Using Biochar-Modified Carbon Paste yielded from Spent Coffee Grounds

Abstract

Dopamine (DA), a crucial neurotransmitter in human systems, coexists with uric acid (UA) and ascorbic acid (AA) in biological fluids, challenging its selective detection due to similar redox behavior. This study introduces a method for selectively preconcentrating dopamine before voltammetric determination. For that, eco-friendly biochar was prepared from spent coffee grounds (400 °C, 60 min), chemically activated with HNO3 (60 °C, 3 h), characterized using FTIR, XDR, and Boehm titration, and then used for assembling carbon paste modified electrodes (CPME). In the electrochemical process, the CPME was immersed in a solution containing the analyte and interferents (0.1 mol l−1 BR buffer, pH = 7.0), and then transferred to the electrochemical cell for detecting preconcentrated DA via differential pulse voltammetry (DPV). The method demonstrated selectivity and sensitivity with a linear dynamic range (LDR) of 10 to 200 μmol l−1, limits of detection (LOD) and quantification (LOQ) of 1.47 and 10.0 μmol l−1. Additionally, synthetic urine samples containing the analyte were analyzed in presence of equimolar concentrations of AA and UA, and the method successfully and selectively determinated DA even in a more complex matrix.