Green liquid supra molecular solvent (SUPRA) phase for fast and selective liquid-liquid micro-extraction of Co²⁺ ions...

The limitation of Liquid-liquid micro-extraction (LLME) procedures can be the need for the use of a dispersive solvent which should be soluble in both of aqueous and organic phases. In this research, a new method named SUPRA-based LLME, is introduced which uses supra molecular solvent (SUPRA), as an environmentally friendly solvent, for quantitative and selective extraction of Co²⁺ ions from its aqueous solution via liquid-liquid micro-extraction process. The aqueous immiscible SUPRA phase, composed of vesicles of decanoic acid was synthesized via ex-situ procedure and used as a single liquid phase. In order to make the SUPRA phase selective, N, N'-disalicylidene-3, 4-diaminotoluene (H₂dst) was synthesized and completely dissolved in the SUPRA phase. Then the lipophilic and selective prepared liquid sorbent, as liquid SUPRA phase, was used for the facile and selective LLME of Cobalt (II) ions from aqueous samples. Experimental studies showed that there was not any need of dispersing solvent and so liquid SUPRA phase could easily dispersed in the aqueous phase and then separated by centrifugation as the supernatant phase. Then the effects of some important variables on the extraction efficiency were also investigated and optimized. The results showed that under optimal conditions, efficient extraction of Cobalt (II) ions was achieved, about 99 % ± 2.7 _(n = 10), in a short time of extraction (10 min), and the linear range of calibration curve was from 500 to 2500 μg L^-1 of Cobalt(II) with correlation coefficient of 0.999. Also detection limit and pre-concentration factor were 150 μg L^-1 and 35.2, respectively. Although the experimental conditions were optimized for extraction of only Co²⁺ ions, the selectivity study showed a high tendency of selective liquid SUPRA phase toward extraction of both of Co²⁺ and Ni²⁺ ions. The matrix effects on the SUPRA-based LLME of Co²⁺ ions from matrix samples, factory wastewater and sea-water, were studied and least matrix effects were observed.