Analysis of β-blocker timolol maleate drug residues in wastewater and biological fluids using differential pulse – anodic stripping voltammetry

Drug residues in water represent one of the most serious environmental problems because of their high toxicity to the biological system. Thus, this study reports a low-cost strategy for fast and precise analysis of β- blocker timolol maleate (TM) using differential pulse anodic stripping voltammetry (DP ASV) at a bare glassy carbon electrode (GCE). At the optimised solution pH 7.2 and other analytical parameters (accumulation time, deposition potential, scan rate, and pulse amplitude), a well-defined oxidation peak was observed at 0.85 V vs Ag/AgCl electrode. The linear calibration range for TM at 0.85 V vs. Ag/AgCl electrode was found to be 5.0 × 10⁻⁷ – 1.3 × 10⁻⁴ mol L⁻¹ (0.21–56.2 μg mL⁻¹) (R ² = 0.9947) with lower limits of detection (LOD) and quantitation (LOQ) of 2.7 × 10⁻⁷ (0.12) and 8.99 × 10⁻⁷ mol L⁻¹ (0.39 μg mL⁻¹), respectively. The developed assay was satisfactorily applied for trace determination of TM residues in biological fluids (urine), environmental water samples and eye drop with good recoveries (90.5 ± 0.66–106 ± 0.66%), demonstrating good accuracy and applicability of the proposed method as an effective and reliable electrochemical sensor for analysis of TM in complex matrices. Common organic and inorganic compounds did not interfere with TM in its determination. The established strategy was validated using the official HPLC method. Analysis results obtained by the present method were comparable to those obtained using the official method; indicating that the proposed method could be used as an alternative method for the routine quality control of the drug in complex matrices. Chromatographic methods are still more precise, while electrochemical sensors are promising for the analyte determination as they have reduced analytical time, low cost and reproducible. The proposed sensor also demonstrated excellent precision, selectivity, and reproducibility for TM determination.