Vortex assisted dispersive liquid–liquid microextraction based on low transition temperature mixture solvent for the HPLC determination of pyrethroids in water samples: Experimental study and COSMO-RS

A green, simple, and effective vortex-assisted dispersive liquid–liquid microextraction method that utilizes a menthol-based low transition temperature mixture (menthol-LTTM-VADLLME) was developed to extract and preconcentrate four types of pyrethroids, namely bifenthrin, deltamethrin, fenpropathrin, and permethrin from water samples. In addition, quantum chemical-based conductor-like screening model for realistic solvents (COSMO-RS) software was used to predict the molecular interaction between low transition temperature mixtures (LTTMs) and pyrethroids based on their σ-profile, σ-potentials, and activity coefficient at infinite dilution. High performance liquid chromatography (HPLC) was employed for the further separation of the pyrethroids and their quantification. Several key parameters that affect pyrethroid extraction efficiency are identified as the vortex time, type of LTTM, volume of LTTM, type of dispersive solvent, dispersive solvent volume, type of salt, and amount of salt. The extraction time of 90 s and 150 µL of menthol: sesamol at ratio 1:1 were selected as the best conditions, while ionic strength and type of dispersant solvent were not relevant for the extraction of the target compounds. After optimization, the menthol-LTTM-VADLLME method was found to be able to detect pyrethroids in the range of 0.5–1000.0 μg/L with good linearity (correlation coefficient = 0.9988–0.9995). The method detection limit and quantification limit were found to be in the range of 0.05–0.11 μg/L and 0.18–0.35 μg/L, respectively. The relative standard deviation of inter-day and intra-day precisions were 2.2–5.0% (n = 5) and 1.2–1.9% (n = 7) respectively. The optimized method can successively determine pyrethroids in tap, drinking and river water samples with good recoveries of 73–111%. Hence, this method presents a good approach for determining pyrethroid content in water samples.