Copper in edible oils: trace amounts determined by atomic absorption spectroscopy.

The application of atomic absorption spectroscopy to trace copper analysis in fats was investigated. Copper spectral resonance lines 3248 A and 3274 A possess the most useful sensitivities applicable to fats and vegetable oils. These sensitivities were determined to be 0.15 and 0.25 ppm in oil, respectively, with detection limits about tenfold lower. Data show that copper absorption depends strictly on the amount of oil aspirated into the flame. In soybean oil-solvent mixtures, aspiration rates decrease logarithmically and linearly with increasing fat content. The accuracy and precision of atomic absorption techniques were established by comparing results from atomic absorption with those from two independent techniques. Error estimates were determined by analysis of copper-hydrogenated soybean oil diluted to low copper levels. The standard deviation, relative standard deviation and analytical error were 0.0108 ppm, 5% and 2.5%, respectively, over a range of 0.05-0.40 ppm copper in soybean oil.