ANALYSIS OF GEOLOGICAL MATERIALS BY ICP-AES WITH CALIBRATION IN CONCENTRATION RATIO

Abstract

A method of calibration in relative concentrations (concentration ratio) previously used only in analysis of non-ferrous and ferrous metals was first implemented when performing silicate analysis of geological materials using atomic emission spectrometry with inductively coupled plasma (AES-ICP). Prior to apply the Concentration Calibration Ratio to analysis of geological materials it is necessary to consider and address the following problems: some of the components are not determined by ICP-AES, matrix elements may be present in different oxidation states. Sample preparation of ores and geological materials was carried out in autoclaves heated at 180°C using HotBlock 200 system. A mixture HCl/HNO3/HF was used at the first step and then added with a 4% H3BO3 solution. The repeatability and intermediate precision of determination when using Concentration Ratio Calibration, calibration without internal standard and Calibration with In as internal standard are compared for determination of SiO2 (content 40 – 75%), Al2O3 (5 – 20%), CaO (0.25 – 15%), MgO (0.1 – 15%), Fe2O3 (0.5 – 15%), Na2O (0.5 – 10%), K2O (0.5 – 5%), P2O5 (0.01 – 0.3%), MnO (0.03 – 0.5%), and TiO2 (0.05 – 2%). The use of Concentration Ratio Calibration provides better metrological characteristics, repeatability and precision in analysis of geological materials compared to other calibration procedures due to elimination of the calibration error of balances and volumetric flasks from total error of analysis; measuring the large intensities of the base element; and better accuracy of measuring the intensity ratio compared to absolute intensity measurements.