Development of an electroanalytical methodology for the determination of dexamethasone using pencil graphite electrodes

Abstract The increasing occurrence of pharmaceutical compounds in aquatic environments has raised concerns about potential impacts on ecosystem integrity and public health. Among these compounds, dexamethasone (DEX), a synthetic glucocorticoid widely used for its anti-inflammatory, antiallergic, and immunosuppressive properties, has attracted attention because of its potential endocrine-disrupting effects and its presence in water bodies. In this work, an electroanalytical method was developed for determining DEX in natural waters using a pencil graphite electrode (PGE). Cyclic voltammetry studies revealed a reduction peak at − 0.93 V vs. Ag/AgCl (3.0 mol L⁻¹ KCl), characteristic of an adsorption-controlled irreversible process, and an oxidation peak at + 0.83 V vs. Ag/AgCl (3.0 mol L⁻¹ KCl), corresponding to a process controlled by diffusion with an adsorption contribution and dependent on the preceding reduction step, possibly referring to the substance generated after the reduction process. Using square-wave voltammetry, linear analytical curves were obtained over the concentration range of 2.00–7.40 µmol L⁻¹. The limits of detection (LOD) and quantification (LOQ) were 0.20 and 0.67 µmol L⁻¹ in ultrapure water (78.5 and 263.0 µg L − 1 ), 0.20 and 0.68 µmol L⁻¹ in tap water (78.5 and 266 µg L − 1 ), and 0.52 and 1.70 µmol L⁻¹ in Billings dam water (204 and 667 µg L − 1 ), respectively. Recovery experiments in dam water yielded 83.7%. These results demonstrate that the proposed method is a simple, cost-effective, and environmentally friendly alternative as a preliminary screening tool for DEX quantification in fortified aqueous matrices, including natural water samples from the Billings Dam.