Cloud point extraction: A sustainable method of elemental preconcentration and speciation

Trace elements are gaining increasing attention of scientists working in various analytical fields. Presence or absence of a trace element in a system seriously modifies its intrinsic behavior. Cloud point extraction (CPE) is an upcoming technology to preconcentrate and separate many of the trace elements from different chemical and biological systems. The system is sustainable as it involves benign extractants like surfactants and that too at low concentrations at slightly elevated temperatures to form clouds that separate out from the bulk solution. In addition, the extraction behavior of many elements depends on its chemical species. Keeping in view the need to summarize the research encompassing this technique, many review articles were published which cover a selection of the literature published on this topic over several time spans. A myriad of various technological developments has been reported by several workers. These developments have prompted us to revisit the CP technology with a better understanding of its detection, mechanism and extension to species dependent extraction behavior with regard to the state of art determination of trace metals in our day to day applications. The present article summarizes mainly the results of trace metal preconcentration using CP methodology from different practical samples with an insight to the probable mechanism and speciation involved from 2006 onwards.