Cloud Point Extraction, Preconcentration, Separation, and Recovery of Zn(II) with Biphenylthiacalix[4]arene Hydroxamic Acid and Trace Determination by ICP-MS

A simple and selective method for separating, preconcentrating, and determining trace amounts of Zn(II) using cloud point extraction and ICP-MS was described. In this process, Zn(II) in an aqueous solution is complexed with biphenyl thiacalix[4]arene hydroxamic acid (BPTC4HA) at an optimal pH of 8.5. Triton X-100 is used as a surfactant, and Na2SO4 is added to lower the cloud point temperature. Phase separation occurs at 45°C, after which the surfactant-rich phase is diluted with acetonitrile-ethanol. Zn (II) is then measured spectrophotometrically at λmax = 330 nm and the extract is inserted into plasma for online ICP-MS measurements. Variables such as pH, temperature, surfactant concentration and reagent concentration were optimized. The method’s selectivity for Zn(II) amidst other ions was examined. Additionally, a transport study using a membrane with a 0.1N HNO3 stripping agent showed 99.9±0.5% transport efficiency for Zn(II) with a half-life of 9.8 min. The detection limit for Zn(II) using spectrophotometry is 0.09 µg/mL, with a quantification limit of 0.3 µg/mL, while ICP-MS enhances sensitivity with a detection limit of 0.05 ng/mL and a quantification limit of 0.16 ng/mL. The method’s reliability was confirmed by testing standard, food, and environmental samples.