2-(5-Bromo-2-Pyridylazo)-5-Dimethylaminophenol (5-Br-DMPAP) as a Reagent for Spectrophotometric Determination of Iron (III)

Abstract

A new colour reaction of iron(III) with 5-Br-DMPAP has been studied systematically. In dilute acetic acid solution (0.06–0.8 N), iron(III) can form a coloured complex with the above-mentioned reagent.The complex exhibits maximum absorption at 600nm, and the value of the apparent molar absorption coefficient is found to be 7.6 × 10⁴. The composition of the complex is also established as Fe(III): 5-Br-DMPAP = 1:2 by the methods of continuous variation and mole ratio, as well as slope ratio. The Lambert-Beer law is obeyed in the range of 0 to 0.8μg iron/ml.

Proposed new method is reasonably selective and sensitive for iron(III) and was satisfactorily applied to the determination of iron(III) in irrigation water.

Key Words:

• Iron(III) determination
• 5-Br-DMPAP
• spectrophotometry
• irrigation water