Determination of ultraviolet filters in water samples by vortex-assisted dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

Abstract

For the first time, a simple solvent microextraction method termed vortex-assisted liquid–liquid microextraction (VADLLME) coupled with gas chromatography–mass spectrometry (GC–MS) has been developed and used for the analysis of six benzophenone ultraviolet (UV) filters (i.e. benzhydrol, 2,4-dihydroxybenzophenone, benzophenone, 2-hydroxy-4-methoxybenzophenone, ethylhexyl salicylate and homosalate) in water samples. The most favorable extraction variables in the VADLLME process were determined. In the extraction procedure, 40μL of tetrachloroethene as extraction solvent were directly injected into a 15-mL centrifuge tube containing 10mL of aqueous sample, adjusted to pH 4 for VADLLME. After VADLLME, the extract was evaporated under a gentle nitrogen gas stream and then reconstituted with N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA), thus allowing the target analytes to be converted into their trimethylsilyl derivatives to optimize the GC–MS analysis. No centrifugation and disperser solvent were required in this microextraction procedure. Significantly, short extraction time and high extraction efficiency were achieved. This method opens up a potentially new horizon for on-site dispersive liquid–liquid microextraction. Under the optimum conditions, the proposed method provided good enrichment factors up to 310, with relative standard deviations ranging from 6.1 to 12.9%. The limits of quantification were in the range of 20–100ng/L, depending on the analytes. The linearities were between 0.05 and 10μg/L and 0.1 and 10μg/L for different UV filters. Finally, the proposed method was successfully applied to the determination of UV filters from spiked genuine water samples and acceptable recoveries over the range of 71.0–120.0% were obtained.