Comparison of three atomic absorption techniques for determining metals in soybean oil

Three different atomic absorption techniques were used to analyze metals contained in three different crude soybean oils. In the first, oil was decomposed by charring followed by high‐temperature dry ashing. The ash then was dissolved in a dilute acidic aqueous medium. In the second, oil diluted with methyl isobutyl ketone as the solvent was aspirated directly. In the third, the original oil sample was ashed and the metal atomized in a sequential process by a carbon rod furnace. This third technique required only μliter quantities of an oil. The analysis for many metals was similar regardless of the technique. However, values obtained for zinc, cadmium, chromium, lead, and calcium were extremely dependent upon the technique used.