Application of aqueous two-phase system for selective extraction and clean-up of emerging contaminants from aqueous matrices.

This review approaches how aqueous two-phase systems (ATPS), in their various compositions (e.g., polymer + salt, copolymer + salt, ionic liquid + salt, acetonitrile + salt), can be efficiently used for extraction, preconcentration, and clean-up of analytes in aqueous samples to determine the compounds classified as emerging contaminants (ECs). In the literature, there are some studies using ATPS applied to ECs, like pesticides, pharmaceuticals, illicit drugs, personal care products, alkaloids, and hormones, even when in trace concentrations. The ATPS is an alternative to the conventional liquid-liquid extraction technique. However, it is predominantly composed of water and do not generally use organic solvents and, therefore, is based on the principles of green chemistry. An ATPS approach has a unique advantage because it can extract neutral, anionic, cationic, polar, and nonpolar compounds, even when present simultaneously in the same sample. This review covers how this simple and low environmental impact technique has been employed for the analysis of different classes of emerging contaminants.

Thermodynamic study of colorimetric transitions in polydiacetylene vesicles induced by the solvent effect.

We report the synthesis of 10,12-pentacosadyinoic acid (PCDA) and PCDA + cholesterol (CHO) + sphingomyelin (SPH) vesicles dispersed in water and the determination of their colorimetric response induced by small amount of organic solvents. In the absence of solvent, PCDA and PCDA/CHO/SPH vesicles showed an intense blue color. The addition of CHCl(3), CH(2)Cl(2), and CCl(4) caused a colorimetric transition (CT) in both structures with the following efficiency: CHCl(3) > CH(2)Cl(2) ≅ CCl(4). However, CH(3)OH did not cause a blue-to-red transition. By microcalorimetric technique we also determined, for the first time, the enthalpy change associated with the CT process and the energy of interaction between solvent molecules and vesicle self-assembly. We observed that the chloride solvents induced a colorimetric transition, but the thermodynamic mechanism was different for each of them. CT induced by CHCl(3) was enthalpically driven, while that caused by CH(2)Cl(2) or CCl(4) was entropically driven.