Eco-Friendly Carbon from Sanguisorba officinalis as an Efficient Electrocatalyst for Separating the Redox Signals of Hydroquinone and Catechol

Catechol (CC) and hydroquinone (HQ) are ubiquitous environmental pollutants and structural isomers that are difficult to separate by conventional methods. In this work, Sanguisorba officinalis biomass was purified and subsequently pre-carbonized and activated to obtain a refined Sanguisorba -derived carbon (RSC). The carbon material was characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Using differential pulse voltammetry (DPV) in phosphate buffer (pH 6.0), the RSC-modified electrode enabled baseline-resolved, simultaneous determination of CC and HQ over 2–24 μM with excellent linearity. The limits of detection were 0.66 μM for CC and 0.67 μM for HQ, respectively. The sensor exhibited good stability (current retention >80% after 100 consecutive cycles), selectivity, and reproducibility (RSD <2%, n = 5), as well as favorable storage stability (>85% signal retention over 15 days). The proposed sensor allows for the individual determination of HQ and CC in river water via the standard addition method, yielding satisfactory recovery results. These results demonstrate that purified, activated herbal biomass can serve as an effective electrode-sensitive material for electrochemical detection, offering a new avenue for the utilization of medicinal-plant-derived carbons in analytical sensing.