Abstract
A method of X-ray fluorescence spectrometric determination with sample preparation and enrichment procedure is described for some heavy metals such as iron, copper, nickel, zinc, lead, bismuth, cobalt and cadmium. This method is based on the preconcentration of metals by solvent extraction of the APDC chelates from hot sample solution into molten stearyl alcohol, the pressing of stearyl alcohol beads to form a suitable X-ray sample and the analysis of the sample by X-ray fluorescence. Stearyl alcohol was found to be an excellent media for collecting microgram quantities of APDC chelates and for subjecting the collected metals to an energy dispersive X-ray fluorescence spectrometer. The samples are treated as disks having intermediate masses per unit area and numerical matrix correction technique is used to linearized fluorescence X-ray intensities for stearyl alcohol disk. APDC extracts heavy metals cited above quantitatively from a 0.5 mol/l sodium acetate or 0.1 mol/l ammonium citrate solution. Iron was, however, not quantitatively extracted from citrate solution, and its chelate was not stable in hot solution. Cobalt was quantitatively extracted only in a narrow pH range (<pH 5). Recovery of the procedure was checked with standard solutions, and it was confirmed that more than 99 % of heavy metals were found in the stearyl alcohol beads. Standard reference materials, Japan standards of iron and steel, No. 506-2 chromium steel and NBS SRM 1570 Spinach, were analysed to test the accuracy of the method. In all case, the close agreement between the cirtificate values and X-ray results is considered to indicate no significant bias in the proposed method.
