Comparison of some preconcentration methods for certain metal ions in human milk and yogurts

Abstract

Five samples each of yogurts and human milk were separately collected, deproteinized, pre-concentrated differently with 1% 8-hydroxyquinoline, 1% ammonium pyrrolidine-dithiocarbamate (APDC) and extracted with methyl-isobutylketone (MIBK). Activated carbon powder in HNO₃ was also used. The extracts obtained were analyzed using atomic absorption spectrometry for some metal ions. In yogurts, the powdered activated carbon in HNO₃ exhibited the highest complexing ability with values of 0.04–0.17, 335–476, 1.52–3.82, 0.08–0.27, 0.09–0.28, 1.31–8.78 and 888–12693 mg/L concentration for Zn²⁺, Mg²⁺, Mn²⁺, Cr³⁺, Cu²⁺, Fe³⁺ and Ca²⁺, respectively. The concentrations of Zn²⁺, Mg²⁺, Mn²⁺, Cr³⁺, Cu²⁺, Fe³⁺ and Ca²⁺ ions were determined to be in the range of 0.02–0.03, 1.10–9.47, 0.05–0.11, 0.02–3.08, 0.01–0.87, 0.47–18.08, <0.01–278 mg/L, respectively, for APDC/MIBK extraction method. The complexing ability of APDC/MIBK appeared to be the lowest. The Co³⁺ and Cd²⁺ ions were only detected by activated carbon pre-concentration method. A more or less similar trend was obtained for human milk samples. For all samples, the complexing ability of each of the complexing agents varied from one metal ion to another.

KEY WORDS: Human milk, Yogurts, Pre-concentration methods, Metal ions determination, 8-Hydroxyquinoline, Ammonium pyrrolidine-dithiocarbamate, Activated carbon powder

Bull. Chem. Soc. Ethiop. 2003, 17(1), 1-9.