Sensitive voltammetric determination of matrine using a nitrogen-doped graphene/zinc oxide nanocomposite modified electrode

A facile one-pot hydrothermal strategy was established to engineer a high-activity sensing interface for quantifying matrine with minimal sample pretreatment. In situ reduction/functionalization of graphene oxide together with ZnO nucleation produced a hybrid film in which nanoparticles were uniformly anchored (20–30 nm) and exhibited distinct (002) lattice fringes (d = 0.26 nm); elemental analysis indicated C 75.6 %, N 4.5 %, O 12.1 % and Zn 7.8 %. Electrochemical probing with [Fe(CN)6]3−/4− showed accelerated interfacial kinetics, decreasing ΔEp from 215 mV (bare) to 62 mV and reducing Rct from ∼880 Ω to 68 Ω. The film enabled a well-defined anodic response for matrine at + 0.95 V, delivering a peak current ∼4.5 × higher than the nitrogen-doped graphene control. Signal optimization identified pH 7.5 as optimal, with Ep shifting linearly with pH (Ep = 1.345 − 0.0582 pH, R² = 0.998), and adsorptive enrichment at open circuit saturating at 240 s. Under these conditions, pulse electroanalysis provided two linear ranges (0.05–10 μM and 10–200 μM) with Ipa = 1.85c + 0.42 (R² = 0.998) and Ipa = 0.64c + 12.61 (R² = 0.997), respectively, and a detection limit of 15 nM (3σ/S, n = 11). Precision was high (18.91 μA at 10 μM, RSD 2.1 %; inter-electrode RSD 3.8 %), with 94.5 % signal retained after 4 weeks at 4 °C and < ±5 % change under common interferents. Standard-addition assays yielded recoveries of 97.8–103.5 % (RSD ≤ 3.9 %) in 100 ×-diluted human serum and quantified 25.6 μM in a Sophora flavescens extract (diluted solution). These figures support routine screening in resource-limited settings.