Natural deep eutectic solvent mixed with powdered cork as a green approach for thin film SPME and determination of selected ultraviolet filters in lake waters

Abstract

An innovative and green determination method of ultraviolet filters, i.e. benzophenone-3 (BZ3), octocrylene (OCR), butyl methoxydibenzoylmethane (BDM) and ethylhexyl methoxycinnamate (EMC), in lake waters was proposed using thin film solid-phase microextraction (TF-SPME) and high-performance liquid chromatography with UV detection (HPLC-UV). A group of six solid natural deep eutectic solvents (NADESs) was tested along with compositions in which these NADESs were combined with powdered cork. All compounds were used as sorbents in TF-SPME for the first time. The NADES containing betaine chloride (BeCl) and 1-eicosanol (EiOH) at a 1:3 molar ratio mixed with powdered cork was finally selected to coat Teflon® mesh. Several factors (pH of samples, mass of sorbent, time of extraction and desorption) were tested using the central composite design in order to select the optimal TF-SPME conditions. Limits of detection ranged from 0.06 to 0.10 ng mL^-1. The relative standard deviations (RSDs) for single sorbent repeatability were lower than 4.6 % (intra-day) and lower than 7.4 % (inter-day), while sorbent to sorbent reproducibility was lower than 8.7 %. Ultraviolet filters were not determined initially in four environmental lake water samples (with summer and winter sampling), however they were determined with good extraction recoveries after spiking the samples (in range of 84–92 % when spiked with 5 ng mL^-1 and in range of 86–95 % when spiked with 50 ng mL^-1). The proposed composition of NADES [BeCl:EiOH(1:3)] and cork at a 15:1 mass ratio exhibits good stability on Teflon® mesh as well as in water and organic solvents which enabled effective extractions for at least 10 cycles. The sustainability and green aspects of the proposed method with NADES/cork composite were analysed using the ComplexMoGAPI tool and established at 85 out of 100. The method exemplifies exceptional innovation by employing natural deep eutectic solvents (NADESs) and cork as sustainable sorbents in TF-SPME – it adheres to green analytical chemistry principles and addresses the critical needs for monitoring ultraviolet filters in water, which is crucial for assessing pollution and environmental health.