Study of the mixed-metal lanthanummagnesium-purpurin complex: spectrophotometric determination of yttrium and lanthanides.

Mixtures of La(III) and Mg(II) form with purpurin (P; 1,2,4-trihydroxyanthraquinone) the mixed-metal complex LaMg(2)P(5), which is extracted with methyl isobutyl ketone at pH 7.5. The molar absorptivity of the complex is 6.1 x 10(4) l.mole(-1).cm(-1) at 570 nm and its conditional extraction constant 5 x 10(13) l(4).mole(-4). Similar complexes have been found to be formed with yttrium, cerium, praseodymium, neodymium and samarium. The use of these complexes for the spectrophotometric determination of yttrium and lanthanides up to 15 mug has been investigated.