Silicate analysis of carbonated rocks using ICP-AES with calibration by the concentration ratio
Calibration by the concentration ratio provides better metrological characteristics compared to other calibration modes when using the inductively coupled plasma atomic emission spectrometry (ICP-AES) for analysis of geological samples and technical materials on their base. The main reasons for the observed improvement are: i) elimination of the calibration error of measuring vessels and the error of weighing samples of the analyzed materials from the total error of the analysis; ii) high intensity of the lines of base element; and iii) higher accuracy of measuring the ratio of intensities compared to that of measuring the absolute intensities. Calcium oxide is better suited as a base when using calibration by the concentration ratio in analysis of carbonate rocks, technical materials, slags containing less than 20% SiO<sub>2</sub> and more than 20% CaO. An equation is derived to calculate the content of components determined in carbonate materials when using calibration by the concentration ratio. A method of ICP-AES with calibration by the concentration ratio is developed for determination of CaO (in the range of contents 20 -100%), SiO<sub>2</sub> (2.0-35%), Al<sub>2</sub>O<sub>3</sub> (0.1-30%), MgO (0.1-20%), Fe<sub>2</sub>O<sub>3</sub> (0.5-40%), Na<sub>2</sub>O (0.1-15%), K<sub>2</sub>O (0.1-5%), P<sub>2</sub>O<sub>5</sub> (0.001 - 2%), MnO (0.01 - 2%), TiO<sub>2</sub> (0.01 - 2.0%) in various carbonate materials. Acid decomposition of the samples in closed vessels heated in a HotBlock 200 system is proposed. Correctness of the procedure is confirmed in analysis of standard samples of rocks. The developed procedure was used during the interlaboratory analysis of the standard sample of slag SH17 produced by ZAO ISO (Yekaterinburg, Russia).