Study On The Pretreating Method Of Sample Before Determinition Of Anions By Ion Chromatography

An Ion Chromatographic method for the determination of anions in Rare Earth products were developed firstly. The pretreated method of sample was studied. The different samples were dissolved and pretreated by different methods. Distillation was used in the pretreation of determining fluoride content in Rare Earth metal and Rare Earth oxide. Indicated by the experiment: it is the optimal condition for distilling that the solution of the sample (being dissolved by 2 mL nitric acid and with four to six drops diffusion agent of HYDSA) had been distilled for 45 min. There are two methods for the pretreation to remove the Rare Earth cations before determining the sulphate content in Rare Earth carbonate or Rare Earth chloride, one is solvent extraction with P507-kerosol solution and the other one is cation exchanging resin column. The optimal condition of extraction indicated by the experiment: the concentration of acid in Rare Earth chloride solution (in hydrochloric system) is pH=l, theamination ratio of P507 is 20 percent, the P507-kerosol solution was used to extract Rare Earth cations of 5 mL sample solution for three times, and 4mL P507-kerosol solution was used every time, and the whole experiment was operated under 15℃. After being extracted, the Rare Earth cations of water phase(concentration is 1.31ng/mL) doesn't deposit with carbonate anion of mobile phase, and the sulfate content can be directly determinated by Ion Chromatography. The optimal condition of cation exchanging resin column was studied: the acid concentration of Rare Earth carbonate is pH=2(in hydrochloric solution system or nitric acid solution system), and 10 mL sample solution (concentration is 0.08g/mL) passed through the cation exchanging resin column for three times, then the sulfate content of solution separated by cation exchanging resin column can be directly determinated by Ion Chromatography. Chloride ion was lixiviated for ten 'minutes in hot water or twenty minutes in cool water from Rare Earth fluoride before the determination on Ion Chromatography, chloride ion can be lixiviated completely with this two methods, the results seem satisfactory. The separation was achieved on an anion separation column, the detection was performed by a conductivity detector, quantitative analysis was conducted" with a calibration curve by measuring the peak area, then anion content was calculated, that is the determination of anions in Rare Earth products. The detection limits of fluoride, sulfate and chloride are 0.0.02pg/mL and 0.006ug/mL respectively. The methods have characteristics of simplicity, rapidity, accuracy, reproducibility and lower detection limits.