COMPLEXATION EQUILIBRIA AND SPECTROPHOTOMETRIC DETERMINATION OF IRON(III) WITH 1-AMINO-4-HYDROXYANTHRAQUINONE

The complex equilibria of iron(III) with 1-amino-4-hydroxyanthraquinon e (AMHA) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaClO4). The complexation reactions were de monstrated and characterized using graphical logarithmic analysis of t he absorbance-pH graphs. A simple, rapid, selective and sensitive meth od for the spectrophotometric determination of trace amounts of Fe(III ) is developed based on the formation of Fe(AMHA) complex at pH 2.5 (l ambda(max) = 640 nm, epsilon similar or equal to 2.1 x 10(4) L. mol(-1 ).cm(-1)) in the presence of a large number of foreign ions. Interfere nces caused by palladium(II) was masked by the addition of cyanide ion s. The method has been applied to the determination of iron in some sy nthetic samples and polymetallic iron ores.