Automated deep eutectic solvent-based chromatomembrane microextraction: Separation and preconcentration of bisphenols from aqueous samples

In this study, an automated, green deep eutectic solvent-based chromatomembrane microextraction approach was developed for separation and preconcentration of organic pollutants from aqueous samples. A design of a chromatomembrane cell (a polytetrafluoroethylene block coated with hydrophobic membranes) ensured automated and continuous liquid–liquid microextraction in deep eutectic solvent and separation of extract phase from aqueous sample phase. It was shown that hydrophobic deep eutectic solvents based on terpene and fatty alcohol/acid can be retained in micropores of the block and acted as a stationary phase in chromatomembrane process. Meanwhile, macropores in the block provide the penetration of aqueous phase and its movement through the block containing the liquid stationary phase (deep eutectic solvent). The large surface contact between the aqueous and deep eutectic solvent phases obtained in the block allowed to achieve on line separation (extraction recovery > 95 %) and preconcentration (enrichment factor > 10). The proposed approach was applied to microextraction of organic pollutants (bisphenols A, E and BP) from aqueous samples followed by their determination by high performance liquid chromatography with fluorometric detection. Under optimal conditions, the limits of detection for bisphenols were 0.03 µg/L. The developed microextraction sample preparation procedure is automated and compatible with liquid chromatography.