Determine the concentrations of heavy metals in mechanically milled maize flour from Kisenyi, Kampala

Abstract

The concentration of heavy metals (Fe,Zn,Mn and Cu) in maize seeds before milling and after milling in different grades of maize flour were determined using the atomic absorption spectrophotometer (AAS). Sample digestion was used to remove the organic matter which allowed easy determination of the concentration of the heavy metals The concentration of manganese in unmilled maize increased from 52.43 mg/L to 57.2 mg/L of grade 80% milling but decreased in 65% and 55% grades of milling to 52.35 and 44.4 mg/L respectively. The concentration of iron in unmillied maize increased from 37.75 mg/L to 46.55 mg/L of grade 55% milling but decreased in 65% and 55% grades of milling to 34.85 and 32.2 mg/L respectively. The concentration of Zinc in unmilled maize decreased from 29.44 to 9.725 mg/L of grade 55% milling. In 65% grade of milling the concentration of Zinc decreased to 4.705 mg/L but in 55% milling the concentration of Zinc increased to 4.865 mg/L. The concentration of copper in unmillied maize decreased from 2.73mg/L to 2mg/L of grade 80% milling. And in 65% and 55% grades of milling the concentration decreased to 1.9 and 1.45mg/L respectively. Generally, there were a decrease of the concentration of heavy metals in the maize flour as the percentage of maize bran removed from the maize seed increased except for manganese and iron in grade 80% milling. The concentration of manganese and iron in milled maize flour where above the permissible values as stated by the W.H.O/F.A.O.