Determination of copper, lead, and nickel in edible oils by plasma and furnace atomic spectroscopies

An atmospheric pressure microwave digestion procedure is described for the determination of copper, lead, and nickel in edible oils. The digestion procedure is compatible with either inductively coupled plasma atomic emission spectrometry (ICP-AES) or graphite furnace atomic absorption spectrometry (GFAAS). Instrument conditions are specified to allow the simultaneous determination of all three metals for each sample introduction. Method detection limits were element-specific but equal to or less than 50 ng/g with ICP-AES and 30 ng/g with GFAAS. Results from spike and recovery experiments at levels of 50, 100, and 200 ng/g are reported for corn and soybean oil. For soybean oil, recoveries at 100 ng/g were 90, 100, and 106%, respectively, for copper, lead, and nickel with ICP-AES, and 89, 106, and 96%, respectively, with GFAAS. Recoveries for corn oil spiked at 100 ng/g were 93, 95, and 103%, respectively, for copper, lead, and nickel with ICP-AES, and 90, 117, and 100%, respectively, with GFAAS. Day-to-day reproducibility was demonstrated by similar method recoveries and reproducibilities in independent analysis of two canola oil sample sets that were spiked at 100 ng/g.