DETERMINATION OF LEAD IN LORANDITE AND MARCASITE BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

In this paper, the methods and the results of lead determination in lo randite and marcasite from the Allchar deposit, by electrothermal atom ic absorption spectrometry, are presented. Since the investigations of the matrix interferences showed that matrix elements, both in lorandi te and marcasite, decrease the lead absorbance, it was necessary to se parate the lead from the matrix. For this purpose, after the decomposi tion of the lorandite sample, thallium was extracted by isoamyl acetat e, first, and then lead was extracted by sodium diethyldithiocarbamate in carbon tetrachloride. By adjusting the pH in the range from 10.5 t o 12.5, arsenic was not coextracted with the lead. Ln the case of marc asite, iron was extracted by isoamyl acetate, and then lead was determ ined directly from the aqueous phase. Using these methods several samp les of lorandite and marcasite from the Allchar deposit were analyzed, and it was found that the lead concentration in lorandite varies from 1 to 2.3 mu g.g(-1) and from 0.7 to 2 mu g g(-1) in marcasite.