Charged species, including Pb<sup>2+</sup> and Cd<sup>2+</sup>, are soluble in water and therefore cannot easily be separated from aqueous solutions for analysis. Cloud point extraction (CPE) is a non-organic phase separation technique that does not use volatile organic solvents and works well to separate metal ions from an aqueous solution. In the CPE for the co-extraction of lead and cadmium, a complexing agent such as dithizone is used to form complexes with the metal ions. Such complexing agents bind to the ions thus neutralizing their charges. The surfactant, an example of which is TritonX-114, can then form micelles around the neutral, hydrophobic complex. Micelles form around the cloud point temperature of the surfactant, for TritonX-114 this is around 25 °C. Once the micellar phase is formed, it can be separated from the aqueous phase by centrifugation. With the metal ions separated from the original aqueous solution, a new solution of a smaller volume can be made from reconstituting the extracted micellar phase. The reconstituted solution has the metal ions from the sample in a higher concentration. Square wave stripping voltammetry (SWSV) can then be used to detect the metal ions in the pre-concentrated solutions. By prefacing SWSV analysis with CPE pre-concentration it is possible to analyze samples with lower concentrations of lead and dadmium. Lowering the detection limit of samples using this technique can allow for the minimization of electrochemical analysis.

CO-extraction of lead and cadmium by cloud point extraction as a pre-concentration method for analysis by square wave stripping voltammetry

253rd National Meeting (2017)

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