No abstract

This work provides a comprehensive evaluation of the effect of the cation alkyl side chain length of the 1-alkyl-3-methylimidazolium chloride series ([CnC1im]Cl, n = 2-14) of ionic liquids (ILs) on their capability to form aqueous biphasic systems (ABSs) with salts and self-aggregation derived properties. The liquid-liquid phase behavior of ternary systems composed of [CnC1im]Cl, water, and K3PO4 or K2CO3 and the respective Setschenow salting-out coefficients (ks), a quantitative measure of the two-phase formation ability, were determined. An odd-even effect in the ks values along the number of methylene groups of the longest IL cation alkyl side chain was identified for the ABS formed by K2CO3, a weaker salting-out agent where the phenomenon is clearly identified. In general, cations with even alkyl side chains, being likely to display higher molar volumes, are more easily salted-out and thus more prone to undergo phase separation. The odd-even effect in the ks values is, however, more significant in ILs up to n = 6, where the nanostructuration/nanosegregation of ILs plays a less relevant role. Still, with the [CnC1im]Cl (n = 7-14) series of ILs, an odd-even effect was also identified in the ILs’ ionization degree, molar conductivity, and conductivity at infinite dilution. In summary, it is shown here that the ILs’ odd-even effect occurs in IL aqueous solutions and not just in neat ILs, an already well-established phenomenon occurring in a series of ILs’ properties described as a result of the orientation of the terminal methyl groups to the imidazolium ring cation and consequent effect in the ILs’ cohesive energy.

Aqueous biphasic systems constituted by ionic liquids (IL-based ABSs) are a target of investigation in the separation of high-value biomolecules. However, identification of the molecular-level mechanisms ruling the two-phase formation and extraction performance of these systems is crucial to the successful design of effective separation processes. In this work, IL-based ABSs formed by K2HPO4 and cholinium carboxylate ILs ([Ch]­[C n CO2] with n = 1–7, comprising anions with odd and even alkyl chain lengths) were investigated. The corresponding ternary phase diagrams, including binodal curves, tie-lines, tie-line lengths, and critical points, as well as the Setschenow salting-out coefficients (k s), which quantitatively describe the two-phase formation ability, were determined at 298 K. The extraction capability of these systems was then evaluated for four amino acids (l-tryptophan, l-phenylalanine, l-tyrosine, and l-3,4-dihydroxyphenylalanine/l-dopa). It was found that ILs composed of anions with even alkyl chains display slightly higher k s values, meaning that these ILs are more easily salted out or more easily phase-separated to form ABSs, whereas ABSs formed by ILs with anions comprising odd alkyl chains lead to slightly higher partition coefficients of amino acids. Beyond the neat IL odd–even effect resulting from their nanostructuration, being this a well-known phenomenon occurring in a series of their thermophysical properties, the existence of an odd–even effect displayed by the IL anion aliphatic moiety in aqueous solution is shown here, visible in both the two-phase formation ability and extraction performance of ABSs. These findings contribute to elucidate of the molecular-level mechanisms governing ABS formation and partitioning of biomolecules, ultimately contributing to the design of proficient separation platforms.

No abstract

Weed management in physic nut plantations has generally been performed by spraying the herbicide glyphosate. However, the effects of glyphosate on non-target organisms present in the crop system are unknown. Here, we evaluated the toxicity of glyphosate (Roundup Transorb(®)) against the pest species Polyphagotarsonemus latus (Acari: Tarsonemidae) and Tetranychus bastosi (Acari: Tetranychidae) which can be exposed by drift. These mites are considered pests of the physic nut; however, they can also feed and reside on weeds associated with the crop, serving as food sources for predatory mites. When subjected to residue (by ingestion of sap of treated plants), and direct contact to glyphosate, P. latus reproduction was affected but T. bastosi was affected only by the residual effect. Although the herbicide caused a reduction in the number of eggs laid by the females of both pest mites, it is suggested that sublethal effects of glyphosate stimulates oviposition of P. latus and T. bastosi: both species displayed higher reproductive rates when exposed to 0.36 kg ha(-1) of the herbicide. We conclude that glyphosate negatively affects the arthropod herbivores studied and we discuss possible implications on their biological control in Jatropha curcas plantations.