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In this work, a carboxylic acid-functionalized graphene (Gr-COOH)-modified glassy carbon electrode (GCE) (Gr-COOH/GCE) was developed and applied for the sensitive determination of hydroquinone in pharmaceutical products. Gr-COOH on a GCE was used as an adsorbent in adsorptive anodic stripping voltammetry (AdASV). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and AdASV were employed to characterize the surface morphology and electrochemical behavior of the Gr-COOH/GCE. The sensitivity of the Gr-COOH/GCE was 3, 7, and 10 times higher than those of a Gr/GCE, GCE-COOH and bare GCE, respectively. Several operational parameters, including the amount of Gr-COOH, preconcentration potential and preconcentration time, were optimized. Under optimum conditions, the peak current response linearly increased with the hydroquinone concentration in the range of 0.1–40.0 μmol l−1 (r = 0.999) with a high sensitivity of 19.86 μA (μmol l−1)−1 cm−2 and a limit of detection of 0.04 μmol l−1. This proposed modified electrode exhibited good repeatability, accuracy and precision. It also showed good anti-interference properties. This method was successfully applied to detect hydroquinone in skin-lightening products.

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