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

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 degrees C, 60 min), chemically activated with HNO3 (60 degrees 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 mu mol l-1, limits of detection (LOD) and quantification (LOQ) of 1.47 and 10.0 mu mol 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. A green electroanalytical method for accurately detecting dopamine in urine, even in the presence of ascorbic acid and uric acid.The use of eco-friendly biochar derived from Spent Coffee Grounds offers a sustainable material for the electroanalysis.Development of a feasible method for dopamine determination without the necessity for sample pretreatment.The use biochar's oxygen groups to selectively accumulate dopamine via pH level adjustments.Excellent analytical precision in measuring dopamine in biological fluids, highlighting its potential for practical applications.