Cloud point extraction of Cr(III) and Cr(VI) ions using novel room temperature ionic liquid N-methyl-N,N-trioctyl-1-ammonium-5,7-diiodoquinoline-8-olate followed by FAAS quantification

Abstract

Room temperature ionic liquid when coupled with cloud point extraction (CPE) has proven to synergistically enhance the efficiency of an extraction process. In the present work, we report the synthesis of a novel room temperature ionic liquid, N-methyl-N,N-trioctyl-1-ammonium-5,7-diiodoquinoline-8-olate (MTAQO) using Aliquat-336 and 5,7-diiodohydroxyquinoline. Infrared, ¹H and ¹³C NMR have been used for characterization. Viscosity of MTAQO has been found to be 4000 centipoise and thermogravimetric analysis (TGA) of MTAQO showed high thermal stability. Lifetime of MTAQO has been recorded along with fluorophore so as to study the application of fluorescence resonance energy transfer (FRET). Cloud point extraction of Cr(III) and Cr(VI) ions has been carried out using MTAQO. Optimization of pH, concentration of non-ionic surfactant Triton X-100, volume of MTAQO, extraction time, centrifugation speed, centrifugation time and dilution solvent have been carried out in order to get maximum extraction efficiency. The quantification has been carried out by flame atomic absorption spectrophotometer (FAAS). Recovery of 97.8% and 99.4%, LOD of 39 ppb and 18 ppb have been observed in the extraction of Cr(III) and Cr(VI) ions respectively. Enrichment factor of 60 has been observed for both Cr(III) and Cr(VI).