A RAPID, SELECTIVE AND SENSITIVE SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF CE(III) USING SOME BISAZOPHENYL-BETA-DIKETONE DERIVATIVES

A rapid, simple, selective and sensitive spectrophotometric method for the determination of cerium(III) using the title azo dyes [1,3-phenyl enediamine bisazoacetylacetone (I-a);1,3-phenylenediamine bisazobenzoy lacetone (I-b);1,4-phenylenediamine bisazoacetylacetone (I-c); and 1,4 -phenylenediamine bisazobenzoylacetone (I-d)] has been developed in ne utral and slightly alkaline (pH 7.00, 7.50, 8.00 and 7.00) media. The 1:1 and 2:1 (M:L) complexes formed exhibit their highest absorbances i n 30% (v/v) dioxane solutions, having formation constants (log K) of 4 .44, 4.95. 5.63 and 5.22 and 8.51, 8.76, 9.73 and 9.37 respectively. B eer's law is obeyed over the concentration ranges 0.10-2.50, 0.05-3.00 , 0.05-3.75 and 0.10-3.50 mu g ml(-1) of cerium(III). More accurately, Ringbom optimum concentration ranges are 0.2-2.25, 0.2-2.6, 0.2-3.5 a nd 0.2-3.3 mu g ml(-1) for the complexes of reagents I-a,I-b,I-c and I -d respectively. The molar absorptivities, Sandell sensitivities and r elative standard deviations were also calculated. The interferences of 50 foreign ions on the determination of cerium(III) were studied. The method allows the determination of cerium(IV) after prior reduction t o the trivalent stare. The proposed method was used for cerium determi nation in two different monazite samples and the results were compared with certified values obtained using atomic absorption spectrometry, indicating that the procedure provided accurate and precise results. ( C) 1997 Published by Elsevier Science B.V.