Two methods for the spectrophotometric determination of uranium (VI) are described. The methods are based on the formation of colored complexes for uranium (VI) with (1)di-2-pyridyl ketone nicotinoylhydrazone (DPKNH), and (2)di-2-pyridyl ketone thiophenoylhydrazone (DPKTH) in 50% (v/v) ethanolic solution. The complexes formed a uranium (VI): complexing reagent mole ratio of 1:2. Maximum absorbance is at 373 nm for U(VI)DPKNH, and at 389 nm for U(VI) - DPKTH. Ranges of linearity, effect of pH, effect of excess reagent, stability of the complexes, and the tolerance limit for many metal ions and common anions have been reported. The two methods have been applied to the determination of uranium in eygeptian monazite sand.
Spectroscopy Letters, Volume 25, Issue 4 June 1992 , pages 585 - 592