Development of ICP-AES method for analysis of iron ore raw materials

A method for the determination of Fe_tot, SiO₂, P, V₂O₅, TiO₂, Cr₂O₃, Ni, Cu, Zn in iron ore raw materials (i.e., pellets, iron ore agglomerate, aspiration dust and slag component of a scrap) by the method of atomic emission spectrometry with inductively coupled plasma (ICP-AES) has been developed using microwave sample preparation in analytical autoclaves. The composition of the acid mixture for the complete dissolution of the sample component, as well as the parameters of microwave decomposition, excluding the depressurization of the autoclave and the loss of sample elements which form volatile compounds are proposed. The developed method of microwave sample preparation in closed autoclaves makes it possible to decompose iron ore samples using the minimum amount of acid (17 cm³) in 45 min. Conditions for the determination of normalized elements in iron ore samples by the ICP-AES method after microwave sample preparation were determined: the operation parameters of the spectrometer were optimized, the analytical lines of each determined element free from spectral overlaps were selected, the efficiency of using cadmium as an internal standard was experimentally proved. The equations for calibration dependences and the ranges of determinable contents are presented. When using cadmium as an internal standard in the analysis of iron ore, a decrease in the value of the standard deviation from 0.17 to 0.04 is observed when determining Cr₂O₃; from 0.02 to 0.004 when determining Fe; from 0.03 to 0.002 when determining SiO₂; from 0.015 to 0.008 when determining TiO₂; and from 0.17 to 0.02 when determining V₂O₅. The correctness of the determination of the standardized elements by the developed method is evaluated, using certified reference samples (CRS) similar in composition to the analyzed material. The results of determining the standardized elements according to the developed methodology were compared with the data obtained using GOST-approved methods of analysis, and then checked in accordance with the Recommendations of RMG 76–2014. The developed ICP-AES technique is characterized by a wider linear range of the determined concentrations than that in GOST-approved techniques, thus providing determination of the components in iron ore raw materials that could not be controlled before. 

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