Observations on the determination of total copper, iron, manganese and zinc in foodstuffs by flame atomic-absorption spectrophotometry

Abstract

A method is described for the determination of total copper, iron, manganese and zinc in foodstuffs. Organic matter is destroyed by wet oxidation and measurement is made directly upon the sulphuric acid digests by flame atomic-absorption spectrophotometry. In the measurement, direct interferences from the inorganic species found in foodstuffs are shown to be a function of burner design and usage. Elimination of these interferences may be achieved for optimum conditions of use, thereby avoiding systematic bias. Isolation of the sources of variation during measurement reveals indirect interferences that enhance the standard deviation of measurement, despite individual presentation of solutions. The accuracy of the method in application to foodstuffs is assessed for the levels of each element normally present. The standard deviations of results are compared with those for measurement alone and the further influence of indirect interferences on the former is inferred. Derived confidence intervals and limits of detection are given for each element.