Toward greener electrochemical sensors: Comparative study of biochar and carbon black as carbon-based materials in...

This study presents, for the first time, a comparative investigation of carbon black (CB) and biochar (BIO) derived from digestate composed of wood and corn silage as carbon-based materials for fabricating disposable screen-printed electrochemical sensors (SPEs). Using a bulk mixing strategy, five SPE variants with different BIO:CB weight ratios (0:100, 25:75, 50:50, 75:25, and 100:0) were prepared and characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), Brunauer-Emmett-Teller (BET) analysis, and cyclic voltammetry (CV). The analytical performance of the sensors was evaluated for the determination of acetaminophen (AC) and its toxic metabolite 4-aminophenol (4-AP) in 0.1 mol L^-1 phosphate buffer (pH 7.4) using differential pulse voltammetry. The obtained sensitivities for AC were 0.088, 0.075, 0.077, and 0.007 μA/μmol L^-1, and for 4-AP were 0.075, 0.090, 0.060, and 0.047 μA/μmol L^-1, corresponding to the SPEs with the BIO:CB ratios of 0:100, 25:75, 50:50, and 75:25, respectively. The sensor with 100 % CB exhibited the highest sensitivity and the lowest limits of detection for both analytes and was selected for the simultaneous voltammetric determination of AC and 4-AP in pharmaceuticals, achieving recovery values between 90.0 % and 106.4 %. These findings provide a direct comparison between CB and BIO studied as electrode materials, showing that under the tested conditions CB delivers the highest analytical performance. Nevertheless, the limited incorporation of renewable BIO is feasible, allowing the electrode composition to be tailored to achieve the desired balance between analytical efficiency and sustainability, thereby supporting the further development of greener and cost-effective electrochemical sensing platforms.