DETERMINATION OF TRACE-ELEMENTS IN HIGH-PURITY ALUMINUM BY TOTAL REFLECTION X-RAY-FLUORESCENCE AFTER THEIR SEPARATION ON CELLULOSE LOADED WITH HEXAMETHYLENEDITHIOCARBAMATES

The determination of trace metals, e.g. Bi, Co, Cu, Fe, Ni, Pb, U, V, Zn, in high-purity aluminium by total reflection X-ray fluorescence (TXRF) following their separation on HMDC-loaded cellulose is described. For preconcentration, trace metals are adsorbed as their hexamethylenedithiocarbamates (HMDC) from acidic aluminium solutions on a reversed-phase cellulose (e.g. acetylated cellulose). The distribution coefficients Kd of the above elements between collector and solution are of the order 104 ml/g. Separation factors of ≥ 105 can be attained using a column or a batch procedure. After preconcentration the trace elements are determined by TXRF (Mo-tube, Ga as an internal standard) and by flame atomic absorption spectrometry (injection technique). Accordingly, the detection limits of the combined TXRF procedure are in the range of 5-20 ng/g depending on the chemical blanks (e.g. Fe, Zn) and the relative standard deviations (n = 5) are in the range of 2.3% (Pb) to 14% (Ni). The accuracy of the analytical procedure is confirmed by TXRF determinations in high-purity reference materials.