Cloud point extraction of Cr, Cu, Cd, and Pb from water samples and determination by electrothermal vaporization inductively coupled plasma mass spectrometry with isotope dilution

Abstract

A simple and efficient cloud point extraction procedure is described for the simultaneous pre-concentration and separation of trace levels of Cr, Cu, Cd, and Pb from water samples and their determination by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The method was based on the formation of hydrophobic complexes of Cr, Cu, Cd, and Pb with ammonium pyrrolidine dithiocarbamate (APDC), followed by their extraction into a small volume of surfactant-rich phase using a non-ionic surfactant, Triton X-l 14. The main parameters affecting the extraction process, such as concentration of the complexing agent and pH and the amount of Triton X-114, were optimized. The surfactant-rich phase was dissolved with nitric acid in ethanol and then injected into the ETV-ICP-MS for Cr, Cu, Cd, and Pb determination. The pre-concentration factor was 14. Isotope dilution was used for quantification. The limits of detection for Cr, Cu, Cd, and Pb were 4, 2, 1, and 1 pg mL-1, respectively. The accuracy of the procedure was verified by analyzing certified reference materials NRCC SLRS-4 River Water and NRCC SLEW-3 Estuarine Water. The reported procedure was applied for the analysis of different types of real world water samples such as tap water, reservoir water, and Love River water collected in the city.