Automation of iron and copper determination in milks using FIA systems and colourimetric detection

This paper describes a flow injection manifold with a colourimetric detection system that enables the determination of iron and copper in different types of milks, namely cow milk and infant formula powdered milks. The methodology used is based on the formation of coloured complexes produced by the reaction of iron (II) with 1,10-phenanthroline and copper (II) with 1,5-diphenylcarbazide. The samples were digested with nitric and sulphuric concentrated acids and inserted in the FIA system without additional treatment. The pH adjustment was carried out inside the manifold including the addition of the reagents needed to form the absorbing species. The sampling rate of both species was never lower than 120 determinations h−1. The results obtained were compared with those given by the reference methods, and the relative deviation was less than 5 and 4% for the determinations of iron and copper respectively. The precision of the results evaluated by the relative standard deviation (RSD%) was less than 0.5% for iron and 2% for copper determinations.