Direct determination of rare earth impurities in lanthanum oxide by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry with slurry sampling

Abstract

Slurry sample introduction with electrothermal vaporization (ETV) has been applied to inductively coupled plasma atomic emission spectrometry (ICP-AES) for the direct determination of rare earth impurities in lanthanum oxide. A polytetrafluoroethylene (PTFE) emulsion was used as fluorinating reagent to form volatile fluorides rather than refractory carbides of rare earth elements (REEs). The flow path of carrier gas between the graphite furnace device and the ICP torch was improved, and the main factors affecting the analytical signals, such as the flow rate of carrier gas and auxiliary carrier gas, matrix concentration, exposure time, vaporization temperature and vaporization time, were studied systematically. Under the optimum operating conditions, the detection limits (DL) for 14 REEs were obtained in the range of 2 ng ml^–1 (Yb) to 130 ng ml^–1 (Ce), and the relative standard deviation (RSD) is less than 5%. The recommended approach has been applied to directly analyse lanthanum oxide without any chemical pretreatment.