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
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%.