An Ion Exchange Separation-Atomic Absorption Spectrophotometric Method for the Determination of Microgram Quantities of Copper, Iron and Zinc in Infant Milk Formula: Powder Form.

An atomic absorption spectrophotometric method is described for the determination of microgram quantities of copper, iron and zinc in infant formula powdered milks. After sample digestion in concentrated nitric acid in a pressure vessel, the solution is evaporated till dryness, and then a solution of 6M HCl is added, in order to form the chlorocomplexes of the metals. This acid solution is passed through an ion-exchange column (anion exchange resin, chloride form). The metals are eluted from the column with diluted acid mixture of 0.005M HCl + 0.5% (v/v) HNO3, and then the eluate is evaporated till dryness. The residue is dissolved in 1% (v/v) HNO3, and then atomized into an air-acetylene flame. A standard addition procedure was employed as a back-up technique. The results obtained by this proposed method and those obtained by the standard addition technique were statistically treated, compared and discussed in this paper.