Hexaacetato calix(6)arene as the novel extractant for palladium

A novel method is proposed for the solvent extraction of palladium. A superamolecular compound, hexaacetato calix(6)arene in low concentration in toluene quantitatively extracts microgram concentration of palladium at pH 7.5. It can be stripped from the organic phase with 2 M nitric acid and determined spectrophotometrically as its stannous chloride complex at 635 nm. The probable composition of the extracted species is Pd(HR)(2)Cl. As low as 1 x 10(-3) M of extractant is adequate for quantitative extraction. Toluene was the best diluent. With nitric and perchloric acid (1.5-3 M) the stripping was complete. Palladium was separated in large ratios from alkali and alkaline earths (1:50). The main group elements were tolerated in higher ratios (1:25), but ions like zinc, cadmium, iron, nickel, platinium, thorium, vanadium and molydenum were tolerated at low concentrations (1:I). The ions showing strong interference were copper, chromium. The relative standard deviation is +/- 1.1%. (C) 1997 Elsevier Science B.V.