Determination of lead species in minerals by thermal atomic-absorption spectrometry

The combined scheme of thermal and atomic-absorption analyses with the use of synthetic minerals for calibration allowed development of a method for i dentifying lead species in solid mineral samples. It is shown that sorbed P b can be reliably separated from other species. Unlike Hg and Cd, determina tion of structurally bound (isomorphous) Pb is problematic because of the o verlapping of peaks of its release with absorption peaks of Pb evaporated f rom its own mineral forms. It is shown that Pb cannot enter the ZnS and CdS structures (less than or equal to similar to 10(-5) wt.%) under hydrotherm al synthesis of minerals at 400 degrees C and 100 MPa. In K-feldspar synthe sized under excess Pb, no more than 1/3 of total Pb may occur as an isomorp hous admixture. It is confirmed that sorption of elements does much to hydr othermal processes. Comparison of data on the heavy-metal system Hg-Cd-Pb s hows that the temperature parameters of the release of an element correlate with its volatility and the thermal stability of its particular species de pending on the bond strength of this element.