In-situ graphene modified pencil graphite electrode for the simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

An in-situ nano-sheet graphene-modified pencil graphite electrode (PGE-NSG) was synthesized via electrochemical exfoliation, a cost-effective and straightforward method. The composition and morphology of PGE-NSG were characterized using Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The binder-free integration of graphene onto the graphite substrate significantly enhanced the electron transfer efficiency compared to the bare PGE, resulting in a 7.8-fold increase in the standard heterogeneous electron transfer rate constant ( k eff 0 ) and a 2.3-fold increase in the electrochemically active surface area. The PGE-NSG-based sensor was employed for the simultaneous electrochemical detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) in ternary mixtures in phosphate-buffered saline (PBS, pH 6.8). Differential pulse voltammetry (DPV) was utilized for quantitative determination, yielding high sensitivities with calibration slopes of 56.9 μA/mM for AA, 37.4 μA/μM for DA, and 11.6 μA/μM for UA. The corresponding limits of detection (S/N = 3) were 30.0 μM for AA, 0.047 μM for DA, and 0.17 μM for UA, with linear detection ranges of 50.0–300.0 μM (AA), 0.05–4.0 μM (DA), and 1.0–15.0 μM (UA), respectively. Furthermore, the sensor exhibited excellent stability and reproducibility, with a relative standard deviation (RSD) of ≤7.3 % ( n = 3) in real sample analysis. These results highlight PGE-NSG as a promising electrochemical sensing platform for the routine AA, DA, and UA analysis, with potential applications in clinical diagnostics and pharmaceutical analysis. • A simple, low-cost approach for directly synthesizing graphene nanosheets on a pencil graphite electrode. • The high surface area of the graphene nanosheet structure significantly enhances electrochemical activity. • Leveraging the synergy between graphene and graphite in PGE-NSG, the sensor achieves high sensitivity, remarkable selectivity, and robust stability for simultaneous detection of AA, DA, and UA. • The developed electrochemical sensor could detect AA, DA and UA level in real samples with reasonable accuracy.