A CRITICAL-REVIEW OF SURFACTANT-MEDIATED PHASE SEPARATIONS (CLOUD-POINT EXTRACTIONS) - THEORY AND APPLICATIONS

The general concept of using the unique phase separation behavior of s ome surfactant micelle solutions as a means for extractive separation is outlined and described. Next, the specific micellar parameters and phase separation behavior of nonionic and zwitterionic charge-type sur factant solutions are summarized. In addition, the phase behavior of s ome derivatized B-cyclodextrin solutions is briefly described. The spe cific applications of such systems and their phase behavior for the ex tractive preconcentration, separation, and/or purification of metal ch elates, biomaterials, and organic compounds are summarized and discuss ed. The potential use of affinity ligands in conjunction with the clou d-point approach for selective bioextractions is also mentioned. The e xperimental protocols, advantages, and limitations of the different cl oud-point extraction techniques are outlined. The use of zwitterionic as opposed to nonionic surfactant media in such separations is compare d and contrasted. In addition, extractions based on use of aqueous two -phase polymer systems are compared and contrasted to extractions empl oying the aqueous surfactant systems. Some areas for further work are identified. The use of such phase separation behavior in environmental cleanup applications is described. Last, some general experimental co nsiderations with respect to surfactant purity and analyte recovery in such systems are presented.