Determination of Phosphorus in Phosphate Ores by Inductively Coupled Plasma-Optical Emission Spectrometry Utilizing an Internal Standard Correction Method

Inductively Coupled Plasma-Optical Emission Spectrometry has been widely used to determine major and minor components in phosphate ores. However, the analysis error caused by instrument drift and matrix effect cannot ignored. In this study, tellurium was used as the internal standard element in order to reduce the instrument drift and matrix effect during determination of high phosphorous content. The relative standard deviation for 12 repeated analyses is 0.5%, which is better than that without calibration (4.1%). The lower detection limit (0.0044%) was achieved by internal standard correction for phosphorus determination. Two kinds of acid digestion methods, aqua regia and a mixture of HCl, HNO₃, HF and HClO₄, for phosphate ore were compared in this work. The results indicate that rapid digestion by aqua regia was suitable for some elements such as phosphorus, calcium, iron, magnesium, manganese analysis, with relative error ranging from-6.7% to 1.6%. The complete digestion of K, Na, Al is related to mineral components and F content of samples. If K, Na, and Al are needed to analyze and there are only a few silicate minerals but a lot of F-bearing components, aqua regia can be used. A mixture of HCl, HNO₃, HF and HClO₄ can completely digest samples and is suitable for determination of P, Ca, Fe, Mg, Al, K, Na, Mn and Sr.