Homogeneous liquid–liquid extraction followed by X-ray fluorescence spectrometry of a microdroplet on filter-paper for the simultaneous determination of small amounts of metals

Abstract

Homogeneous liquid–liquid extraction with perfluorooctanate ion (PFOA^–) was utilized for the preconcentration of certain types of metal chelates, such as diethyldithiocarbamate, 1,10-phenanthroline and desferrioxamine B. Under the experimental conditions {i.e., [PFOA⁻]_T = 6.0 × 10⁻³ mol l⁻¹, [acetone]_T = 2.0 vol%, [HCl]_T=0.72 mol l⁻¹, room temperature}, the maximum concentration factor was 500-fold. A method was then developed to determine those metal chelates deposited in a microdroplet on filter-paper using X-ray fluorescence spectrometry. As a result, when three types of chelating agent were used together in the process, 15 metal ions [Ti(IV), Zr(IV), V(V), Nb(V), Ta(V), W(VI), Fe(II), Co(II), Ni(II), Pd(II), Cu(II), Au(III), Hg(II), Bi(III) and Se(IV)] were simultaneously determined. The recovery of each metal was ca. 83–100%, except for W(VI) which was 60.2%. The calibration curves for each metal ion were linear over the range from 5.0 × 10⁻⁷ to 1.0 × 10⁻⁵ mol l⁻¹. The detection limits were at the 10⁻⁸ mol l⁻¹ level and the relative standard deviations were below 5%.