Green synthesis of Mn2O3-Mn3O4 nanocomposite using Clitoria ternatea L. (Bluebutterfly) flowers extract and its colloidal gel based microextraction application

Abstract

In this study, Mn₂O₃–Mn₃O₄ nanocomposite was synthesized using water extract of Clitoria ternatea L. flowers. A colloidal gel of the synthesized nanocomposite was prepared using a choline chloride/phenol (1:2) deep eutectic solvent (DES). The synthesized nanocomposite and colloidal gel were characterized by SEM, TEM, SAED, XRD, and FT-IR spectroscopy. Subsequently, a Mn₂O₃–Mn₃O₄/DES-based colloidal gel extraction method was developed for the separation and preconcentration of methylene blue from water samples prior to UV–Vis spectrophotometric determination. Response surface methodology (RSM) based on a Box–Behnken design was employed to optimize the main experimental parameters, including nanocomposite amount, sample volume, colloidal gel volume, and pH. The linear, interaction, and quadratic effects of these parameters on the extraction performance were also evaluated. Under the optimized conditions, the developed method exhibited a working range of 2–120 µg L⁻¹, with a coefficient of determination (R²) of 0.994, a limit of detection (LOD) of 0.56 µg L⁻¹, and an enrichment factor (EF) of 33.6. The developed method was subsequently applied to real water samples. The greenness of the method was evaluated using the AGREE tool, demonstrating that the proposed method provides a reliable and sustainable alternative for the routine determination of methylene blue in water samples.