Biopolymer-based ultrasound extraction of parabens: Functionalized polyvinylpyrrolidone –alginate beads with a natural eutectic solvent

Parabens, widely used as preservatives in pharmaceuticals and personal care products, are considered emerging contaminants due to their endocrine-disrupting properties and frequent detection in aquatic environments. Their trace-level concentrations (μg L^-1 to ng L^-1) and moderate polarity pose significant challenges for effective monitoring using conventional preconcentration techniques. To address these limitations, a green ultrasound-assisted extraction method was developed employing polyvinylpyrrolidone-alginate beads functionalized with a hydrophobic natural eutectic solvent composed of menthol and camphor (2:1 M ratio). The sorbent facilitates selective interaction with parabens through hydrogen bonding and hydrophobic effects, significantly improving extraction efficiency over non-functionalized materials. The method utilises only 125 mg of biodegradable sorbent and 3 % ammonia in water as desorption solvent, per analysis, minimising the use of hazardous reagent and aligning with Green Analytical Chemistry principles. Under optimised conditions, four parabens i.e., methylparaben, ethylparaben, propylparaben and butylparaben, were simultaneously extracted and analysed by UHPLC-DAD, achieving enrichment factors ranged from 8 to 13.9, with limits of detection and quantification between 0.056 and 0.222 μg L^-1 and 0.186-0.744 μg L^-1, respectively. Precision (RSD) remained below 10 % for both intra- and inter-day analyses, with excellent linearity (R² ≥ 0.9943) across a working range of 5-10,000 μg L^-1. The method was successfully applied to wastewater samples from various treatment stages, achieving recoveries between 81 and 114 %, confirming its suitability for routine environmental monitoring of parabens.