Di-(2-ethylhexyl)phosphoric acid-based hydrophobic deep eutectic solvent as a carrier for ferrofluid: application for rapid determination of bisphenol A in water samples.

A hydrophobic deep eutectic solvent composed of di(2-ethylhexyl)phosphoric acid and menthol was synthesized and employed as the carrier liquid for the development of a new ferrofluid for liquid-phase microextraction of bisphenol A (BPA) from water samples. The methodology comprised stirring the water sample with a specified volume of ferrofluid, magnetic separation of the phases, and subsequent desorption of BPA using ethanol. No centrifugation was required, and the microextraction process took approximately 3.5 min. The obtained extract was subjected to analysis by high-performance liquid chromatography equipped with ultraviolet detection. The method demonstrated linearity across the concentration range of 2.5-200 μg L-1 with an r2 value of 0.9985. A limit of detection of 0.8 μg L-1 was achieved, with intra-day and inter-day relative standard deviations not exceeding 6.9%. The developed method was employed to determine the concentration of BPA in drinking and mineral water samples, yielding recovery values ranging from 85.2 to 99.7%. Although BPA was not detected in the drinking water, but appeared in the same water after boiling and cooling in both paper and plastic cups, with results confirmed by gas chromatography-mass spectrometry analysis, demonstrating the significant potential of the method for extracting BPA from water samples.