Determination of carbon in praseodymium neodymium fluoride- lithium fluoride electrolyte by high-frequency combustion infrared absorption method
HAO Huicong1,2, YANG Fan1,2, ZHANG Xiuyan1,2, FAN Xiaolong1,2, REN Xudong*1,2
1. Baotou Research Institute of Rare Earths, State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization,Baotou 014030,China; 2. Ruike National Engineering Research Center of Rare Earths Metallurgy and Function Materials,Baotou 014030,China
Abstract：Accurate determination and control of carbon content in praseodymium neodymium fluoride-lithium fluoride electrolytes is of great significance for the monitoring of praseodymium neodymium alloy production process and the quality of finished products. A method for the determination of carbon content in praseodymium neodymium fluoride-lithium fluoride electrolyte by high-frequency combustion infrared absorption was established. The analytical time was controlled at 35 s, and the sampling mass was 0.20-0.30 g. The standard sample of steel was used for the preparation of single-point calibration curve. Tungsten, tin, and iron were selected as the flux. An orthogonal experiment with four factors and three levels was designed, and the investigation factors includes the mass of tungsten, the mass of tin, the mass of iron, and the adding sequence of flux and sample. Through the experiments, the adding sequence of flux and sample was pure iron + sample + tungsten and tin. The dosage of flux was 0.60 g of iron, 1.20 g of tungsten, and 0.40 g of tin. The limit of detection of method was 0.000 255% (mass fraction, the same below), and the limit of quantification was 0.000 85%. Three different batches of praseodymium neodymium fluoride-lithium fluoride electrolyte samples were measured according to the experimental method, and the relative standard deviations (RSD, n=11) of determination results were between 2.8% and 3.3%. The Grubbs outlier judgment method was used to identify the outliers. The Grubbs GMax of measurement results of three batches was 1.463, 1.503, and 1.335, and the GMin was 1.704, 1.639, and 1.669, respectively. They were all less than the Grubbs critical value G(0.05,11)=2.234 (significant level α=0.05), indicating that there were no abnormal values in the measurement results. The standard steel sample was used into the sample for spiked recovery tests, and the recoveries were between 96% and 105%.
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