Tunable solvency mixtures of tetrahydrofuran: water for efficient and fast extraction/clean-up of trace contaminants

Abstract

In this study, we investigated the potential of mixtures of tetrahydrofuran (THF) and water as tunable solvents for the microextraction of contaminants in solid and in liquid matrices. These two miscible solvents have very different dielectric constant and Hildebrand solubility parameters, so that tunable mixtures spanning a wide range of dispersion and hydrogen bonding forces could be easily prepared by simply changing their composition. In this way, rapid and more efficient extraction methods can be developed. A liquid-liquid and a solid-liquid microextraction method for the determination of bisphenol A (BPA) in urine and ochratoxin A (OTA) in cereal baby food were developed as a proof of concept. Both, the chemical composition and the relative solvency of the THF-water mixtures, expressed as Teas solubility parameters, were studied in order to gain some insights into the chemical interactions governing analyte extraction. For urine, the salting-out extraction with THF:water and NaCl was evaluated, a process which is still scarcely investigated for analytical purposes. These methods featured good recoveries (above 95%), satisfactory standard deviation (5–6%) and good sensitivity (detection limits of 0.l μg L−1 for BPA and of 0.l ng g-1 for OTA) with the advantages of simplicity, rapidity and low consumption of reagents. Recoveries for other compounds and matrices (bisphenols ad phosphorus flame retardants in dust and in tap water, dyes in tap water and OTA in powder milk) were also assessed to prove the wide potential of these tunable solvent mixtures.