Trace analysis of lead in oil by TLC

Summary

Trace amounts of lead contaminating a specimen of mineral oil were succesfully determined by TLC after concentrating the metal on microcrystalline cellulose, calcining and preparing final samples by take-up of the residues in small volumes of HCl. This method may also be applicable to other oils and to fats. Final determinations are made, after chromatographic separation of lead from other elements, by fluorimetric scanning of the chromatograms. Results are reliable with samples containing between 0.002 and 0.1 ppm of Pb, using a sample size of 25 cm³. With Pb contents below 0.002 ppm, lead contamination of the chemicals used may cause difficulties, and the sample size must be increased. In contrast, when more than 0.1 ppm of Pb is expected, sample sizes should be reduced. Sulphate ions interfere, and should be removed with BaCl₂ before chromatography.