Applicability of liquid-liquid extraction to increase sensitivity of determination of fourth period transition metals in iron ores by total-reflection X-ray fluorescence analysis

The presence of intensive X-ray fluorescence of iron as well as escape peaks in the spectrum of geochemical samples has a negative impact on direct quantification of low amounts of neighboring elements. In this paper, using the analysis of iron ores as a case study, it is shown that removal of the iron matrix by liquid-liquid extraction improves the sensitivity and accuracy of determination of fourth-period transition metals (Ti, V, Cr, Mn, Co, Ni, Cu, Zn) compared to direct suspension analysis. A procedure involved acid digestion of ore powder by aqua regia, Fe removing with methyl isobutyl ketone from hydrochloric acid medium, TXRF measurement of aqueous phase containing Ga as an internal standard. Intralaboratory precision calculated using duplicate sample preparations ranged from 1 to 9 % for all considered elements. After extraction of iron, it became possible to determine Co, V, Cr and Ni which weren't detected in iron ore samples using direct analysis. However, for some samples, determination of Cr can be considered only as semi-quantitative because minerals containing Cr did not fully dissolve during acid decomposition.