DETERMINATION OF LEVELS OF SELECTED HEAVY METALS IN RAW AND POWDER MILK PRODUCTS AVAILABLE IN HARAR CITY MARKETS, ETHIOPIA

Abstract

Milk is a white liquid produced by the mammary glands of mammals and used for different purposes especially for human as food. However, its contamination with heavy metals is a great problem for the required purpose. Based on this, this study aimed on determination of levels of selected heavy metals in raw and powder milk products from Harar city markets using flame atomic absorption spectroscopy (FAAS) via wet-acid digestion method. The digestion procedure was optimized by varying reagent volume, digestion time, and temperature to develop a procedure that consumes less reagent volume, give a clear solution, and requires minimum digestion time and temperature. The optimum conditions were found to be acid mixture of 5 mL of HNO3 and 3 mL of HClO4, digestion time of 2 h and 15 min, and digestion temperature of 180 oC for the digestion of 0.5 g powder milk and 1.25 mL raw domestic milk samples. The digestion procedure was evaluated by spiking method with recoveries in the range of 94.4-102% and the standard deviations less than10%. Using these optimized conditions prior to FAAS analysis, the concentrations of Cu, Mn, and Fe in the milk were found to be in the range of 27.3-49.5, 2.07–43.8, and 5.27-94.5 ppm, respectively, and Ni was not detected (ND). Based on standards, the concentration levels of the heavy metals are not above the required concentration which can be consumed by human. Therefore, the milk products can’t cause problem on human health based on heavy metal concentration