Extractive spectrophotometric determination of uranium with Malachite Green

A sensitive spectrophotometric method based on the extraction of a uranium-benzoate-Malachite Green complex by chlorobenzene is described. The absorption maximum is at 635 nm and the molar absorptivity is 8.3 x 10(4) 1 mole(-1), cm(-1). A preliminary separation of uranium by extraction with methyl isobutyl ketone from acid-deficient aluminium nitrate solution is used to avoid interferences. An aliquot of the extract is then diluted with chlorobenzene and shaken with benzoate buffer containing Malachite Green (MG). The method has been applied for the determination of uranium in a synthetic leach solution. The complex extracted is probably MG(2)(C(6)H(5)COO)(3)]MG(+)].