Combined cloud point-solid phase extraction by dispersion of TiO2 nanoparticles in micellar media followed by semi-microvolume UV–vis spectrophotometric detection of zinc

A new approach is presented in this paper by using dispersed TiO2 nanoparticles (TiO2-NPs) in a combined cloud point and solid phase extraction for the efficient preconcentration and determination of Zn2+ in various samples. In this method Zn2+ ions are adsorbed on TiO2-NPs and transferred into surfactant rich phase. Subsequently the Zn2+ ions are desorbed from TiO2-NPs by a dithizone solution via forming a color complex which could be detected colorimetrically. The influence of chemical variables such as pH of the sample solution, electrolyte, amount of TiO2-NPs, type and volume of the eluent on the extraction system was studied. The calibration graph was linear in the range of 0.5–90.0 µg L−1 of Zn2+ (r=0.9996). An enrichment factor of 80 was achieved and the limit of detection for Zn2+ was 0.33 µg L−1. The relative standard deviation (RSD) for eight replicate measurements of 10 µg L−1 and 60 µg L−1 of Zn2+ was 1.8% and 1.5% respectively. The proposed method was successfully applied to the quantitative determination of Zn2+ in tap water, powder milk and Zinc sulfate tablet with satisfactory results.