Date palm biochar-modified SPCE for simultaneous electrochemical detection of hydroquinone and catechol

The development of low-cost electrochemical sensors for the simultaneous detection of structurally similar phenolic pollutants remains challenging, particularly due to overlapping redox responses and the complexity of many nanostructured sensing platforms. Herein, a biochar-based electrochemical sensing platform is developed for the sensitive and simultaneous detection of phenolic contaminants in water. The biochar, obtained from date palm rachis waste through pyrolysis, provides a functional carbon material with intrinsic porosity and abundant surface active sites. The material is easily integrated onto a screen-printed carbon electrode (SPCE) via a simple drop-casting approach, enabling the fabrication of a disposable sensing device. Although biochar-based and SPCE-based electrochemical sensors have shown promising analytical performance, many previously reported systems still require multistep fabrication strategies, costly materials, or show limited peak discrimination for structurally similar phenolic compounds. The resulting sensor enables reliable simultaneous determination of hydroquinone (HQ) and catechol (CC), two phenolic isomers characterized by closely overlapping redox potentials. Differential pulse voltammetry enables clear peak separation and accurate quantification of both analytes, overcoming the poor peak discrimination typically observed at unmodified electrodes. Electrochemical characterization demonstrates that biochar modification significantly enhances electron-transfer kinetics and increases the electroactive surface area compared to the bare electrode. The sensor exhibits a wide linear range (0.01 μM–500 μM) and low limits of detection (0.46 μM for HQ and 0.18 μM for CC), along with good repeatability, stability, and resistance to mutual interference. Notably, the analytical performance is competitive with that of more complex nanostructured systems, while relying on a simpler and more environmentally friendly fabrication strategy. Overall, these results highlight the potential of waste-derived biochar as an efficient electrode modifier, offering a scalable solution for the development of low-cost electrochemical sensors for environmental monitoring.