Magnetic retrieval of a switchable hydrophilicity solvent: fast homogeneous liquid-liquid microextraction for the determination of benzophenone-type UV filters in environmental waters

A fast and simple homogeneous liquid-liquid microextraction method has been developed for the extraction of three benzophenone-type UV filters (4-hydroxybenzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone) from environmental waters prior to analysis by liquid chromatography-ultraviolet detection. Di-(2-ethylhexyl)phosphoric acid was used as a switchable hydrophilicity solvent and its initial conversion into hydrophilic form was carried out in the alkaline solution, while its hydrophobic form extracting the analytes was generated by mineral acid addition. After the extraction process was completed, unmodified Fe3O4 magnetic nanoparticles were used as a carrier to separate and retrieve the switchable hydrophilicity solvent from the sample solution. The magnetic retrieval process was highly effective based on the complexation of the phosphoric acid head group of solvent with the surface metal atoms of the nanoparticles. Under optimal extraction conditions, the extraction recoveries of the studied compounds were obtained in the range of 69-93%. The limits of detection for the analytes were between 0.7 and 0.8 mu g L-1. Relative standard deviations were less than 6.0% for intra-day and 7.9% for inter-day precision. The microextraction of related UV-filters from a variety of environmental waters was carried out efficiently. The recoveries obtained from spiked water samples were in the range of 80-103%.

Automated summary

A fast and simple liquid-liquid microextraction method was developed for the extraction of benzophenone-type UV filters from environmental waters. Di-(2-ethylhexyl)phosphoric acid was used as a switchable hydrophilicity solvent and Fe3O4 magnetic nanoparticles were used as a carrier for the solvent retrieval. The method showed high extraction recoveries and efficient microextraction of the UV filters from various environmental waters.