Rapid and precise methods have been studied for the determination of microamounts of lead in fatty oils, fatty acids and their derivatives. The sample was carbonized with sulfuric acid by heating in the range of 250° to 280°C, and then 30% hydrogen peroxide was gradually added to destroy organic matter. By Applying this method, the digestion was carried out rapidly as compared with conventional methods such as dry ashing and wet digestion.
Lead in the digested solution obtained was determined by spectrophotometric determination and atomic absorption spectrometry. In the former method, lead was extracted as dithizone complex from the digested solution, and then the extract was determined spectrophotometrically by using the maximum absorbancy at 520nm. In the latter method, complex produced by adding sodium diethyldithiocarbamate was extracted with methyl isobutyl ketone. The extract was directly injected into an air-hydrogen or air-acetylene flame, and a spectral line of lead was measured at 283.3nm. The proposed methods were tested by carrying out collaborative studies on samples which had been artificially prepared by adding known amounts of lead to soybean oil. The results obtained corresponded to a satisfactory agreement with the theoretical values.
