Spectrophotometric determination of ferric, ferrous, and total iron in drugs by reaction with alpha, alpha'-dipyridyl.

The drug sample is dissolved in 0.2N HCl to yield a final concentration of 30 mug Fe/ml, an aliquot is reacted with alpha,alpha-dipyridyl, and the pH is adjusted with an acetate buffer. For Fe(II), the color intensity is measured at 523 nm. For total iron, ascorbic acid is added to a separate aliquot of the sample solution, reducing all the iron present to Fe(II), which is then reacted with alpha,alpha'-dipyridyl, diluted to volume, and read at 523 nm. The Fe(III) content is determined by subtracing Fe(II) from total iron. This method is applicable to iron-containing drugs and drug dosage forms.