Analytical Sciences

Extraction Separation and Electrothermal Atomic Absorption Spectrometric Determination of Thallium in Some Sulfide Minerals

Dragica ZENDELOVSKA*  and Trajcce STAFILOV**

*Institute of Preclinical and Clinical Pharmacology with Toxicology, Faculty of Medicine, St. Cyril and Methodius University, 50 Divizija, 1000 Skopje, Macedonia
**Institute of Chemistry, Faculty of Science, St. Cyril and Methodius University, POB 162, 1001 Skopje, Macedonia

A method for thallium determination in some sulfide minerals (sphalerite, galena, orpiment and realgar) by electrothermal atomic absorption spectrometry has been proposed. Mineral samples were dissolved in a mixture of HNO₃ and HCl. The effect of interfering elements (Zn, Pb and As) on the determination of Tl in the investigated minerals was studied. These investigations show that it is not possible to determine thallium directly from solutions obtained by dissolution of minerals in mineral acids, because these matrix elements tend to decrease the absorbance of thallium. Also, it was found that the investigated minerals contain iron that tends to increase the absorbance of thallium. Therefore, a method for extraction of thallium with isoamyl acetate from 10 mol/l HCl media was proposed. In these conditions, Zn, Pb and As remain in the inorganic phase, but iron and thallium are extracted into organic phase. Reextraction of iron from the organic layer was performed with 4 mol/l H₂SO₄ . The determination of thallium was performed in the organic phase using Pd as modifier. The investigated sulfide minerals originated from different mines from the Republic of Macedonia. The relative standard-deviation range was between 2.20 to 3.92%. The detection limit of the method (calculated as 3SD of the blank) was found to be 0.05 ug/g.

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