Extraction of uranium(VI)-pyridylazo dye complexes into a droplet of lipophilic polyoxyethylene nonyl phenyl ether (PONPE-2) for subsequent spectrophotometry

Polyoxyethylene nonyl phenyl ether with 2 oxyethylene units (PONPE-2) is immiscible with water and is suspended on the surface of aqueous layer as a droplet. Its unique property is applied to the solvent extraction of uranium(VI) with 5-Br-PADAP. Uranium(VI) chelates are quantitatively enriched into a small volume of PONPE-2 and the absorbance was measured in the mixed ethanol solution. The apparent molar absorptivity of uranium(VI)-5-Br-PADAP complex at 578 nm is 6.46×10⁴ l mol^–1 cm^–1 and the calibration curve is linear over the range of 0.7–7 g of uranium(VI) per 1.5 ml of the final solution.