Complex formation equilibria of iron(III) with 2-hydroxy-3-pyridinol and 2-mercapto-3-pyridinol. Spectrophotometric determination of iron(III) in multivitamins

The complex equilibria of iron(III) with 2-hydroxy-3-pyridinol (HHP), and 2 -mercapto-3-pyridinol (MHP) were studied spectrophotometrically in 40% (v/v ) ethanol and an ionic strength of 0.1M (NaClO4). The complexation reaction s were demonstrated and characterized using graphical logarithmic analysis of the absorbance pH-graphs. After considering all the different parameters a simple, rapid, sensitive and selective method for spectrophotometric det ermination of trace levels of iron(III) was proposed based on the formation of (Fe -MHP) complex at pH 2.5 (lambda(max) = 640 nm, epsilon = 1x10(-1) L mol(-1) cm(-1)). The interference of a large number of foreign ions was in vestigated. The method has been applied successfully for the determination of iron content in some multivitamins with mineral preparations and infant milk products.