A Green and Sustainable Approach for Melatonin Determination: Comparative Assessment of Hybrid Micellar Liquid Chromatography and Differential Pulse Voltammetry

Melatonin, the main indolamine compound in the pineal gland, which plays a role in the regulation of biological rhythms and shows promise in the treatment of sleep disorders, is widely used today. In this study, the determination of melatonin in tablet formulations was comparatively evaluated using hybrid micellar liquid chromatography (HMLC) and differential pulse voltammetry (DPV) methods. The compound was analyzed by the HMLC method in a water–ethanol binary mixture containing 0.05 M sodium dodecyl sulfate and 20% ethanol (v/v) adjusted to pH 7.5. It was then determined by the DPV method using a gold electrode in Britton-Robinson buffer (pH 5.0). The results were systematically analyzed, the analytical methods were validated, and a comprehensive comparison was conducted. Under optimized conditions, the HMLC method yielded melatonin concentrations between 2.0 and 8.0 μg/mL (r = 0.999); the DPV method showed a linear calibration range between 1.9 and 139.4 μg/mL (r = 0.997). The LOD values for the HMLC and DPV methods were 0.335 μg/mL and 0.481 μg/mL, respectively; the LOQ values were 1.016 μg/mL and 1.456 μg/mL, respectively. The mean recovery was 99.57% for HMLC and 100.39% for DPV. The suitability of the developed methods for the 12 principles of green analytical chemistry (GAC) and the white analytical chemistry (WAC) approach was evaluated using established tools. This study presents, for the first time, a comparative evaluation of HMLC and DPV methods for melatonin determination within the framework of green and white analytical chemistry, using a nontoxic micelle mobile phase and an unmodified gold electrode.