An improved ashing procedure for the determination of heavy metals in edible oils

An accurate, reliable, and simple method was described for the determination of Pb, Cu, Cd, Mn, Zn, an d Fe in edible oils by atomic absorption spectrophotometry following burning of the sample in a restricted air supply. Recoveries for the six heavy metals by the proposed methods were about 100%. The relative standard deviation of the analysis for the lead at the level of 0.074 ppm was 6%, and the copper at the levels of 0.064 ppm and 0.158 ppm were 7% and 2%, respectively. The recovery of lead was found to be suppressed by the presence of a large quantity of iron in the oil, but the suppression was alleviated by adding a Mg(NO3)2 solution to the charred residue before ashing.