Determination of UV filters in high ionic strength sample solutions using matrix-compatible coatings for solid-phase microextraction.

A double-confined polymeric ionic liquid (PIL) sorbent coating was fabricated for the determination of nine ultraviolet (UV) filters in sample solutions containing high salt content by direct immersion solid-phase microextraction (DI-SPME) coupled to high-performance liquid chromatography (HPLC). The IL monomer and crosslinker cations and anions, namely, 1-vinyl-3-decylimidazolium styrenesulfonate ([VImC10][SS]) and 1,12-di(3-vinylbenzylimidazolium) dodecane distyrenesulfonate ([(VBIm)2C12] 2[SS]), were co-polymerized to create a highly stable sorbent coating which allowed for up to 120 direct-immersion extractions in 25% NaCl (w/v) solution without a decrease in its extraction capability. Extraction and desorption parameters such as desorption solvent, agitation rate, extraction time, desorption solvent volume, and desorption time were evaluated and optimized. The analytical performance of the styrenesulfonate anion-based PIL fiber, PIL fiber containing chloride anions, and a commercially available polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber were compared. Coefficients of determination (R2) for the styrenesulfonate anion-based PIL fiber ranged from 0.995 to 0.999 and the limits of detection (LODs) varied from 0.1 to 5 µg L-1. The developed method was successfully applied in real water samples including tap, pool, and lake water, and acceptable relative recovery values were obtained. The lifetime of the PIL fiber containing chloride anions as well as the PDMS/DVB fiber were considerably shorter than the PIL fiber containing the styrenesulfonate anion, with both fibers showing a notable decrease in reproducibility and significant damage to the sorbent coating surface after 40 and 70 extractions, respectively. The R2 values for the chloride anion containing PIL fiber were at or higher than 0.991 with LODs ranging from 0.5 to 5 µg L-1. For the PDMS/DVB fiber, R2 values ranged from 0.992 to 0.999 and LODs were found to be as low as 0.2 µg L-1 and as high as 5 µg L-1.