Hydrophobic natural deep eutectic solvents based on L-menthol as supported liquid membrane for hollow fiber liquid-phase microextraction of triazines from water and urine samples

Abstract

This work proposes the use of a hydrophobic natural deep eutectic solvent (NADES) as a supported liquid membrane (SLM) for hollow fiber liquid phase microextraction (HF-LPME) of triazines. NADES were prepared using L-menthol as hydrogen bond acceptor combined with different hydrogen bond donors of natural origin: carboxlylic acids, alcohols and amines. Studies were carried out to determine whether the prepared NADES met the necessary requirements to be used as a SLM, such as stability in the HF and compatibility with HPLC. Then, the ability of each prepared NADES to extract 6 triazine herbicides by HF-LPME from aqueous samples was evaluated. Among them, the mixture L-menthol: formic acid (molar ratio 1:2) provided better extraction results and was selected as SLM. The influence the different parameters on extraction efficiency such as pH of both sample and acceptor solution, salting-out effect, extraction time and stirring rate on the extraction efficiency was carefully studied and optimized. The optimized HF-LPME procedure was applied to the analysis of aqueous samples such as artificial water containing humic acids, tap water, river water and urine, with excellent clean-up ability for all samples analyzed. Relative recoveries ranged from 68 to 128 %, and the LODs and LOQs obtained for the 6 triazines were 0.75–3.1 µg/L and 2.5–10.3 µg/L, respectively, depending on the analyte and the kind of sample. Additionally, according to the AGREEprep tool assessment, the proposed method appears as a greener approach compared to other microextraction methods reported in the literature for the analysis of triazines in water samples.