APPLICATION OF ICP-AES TO THE DETERMINATION OF RARE-EARTH ELEMENTS IN PHOSPHATE SAMPLES

ICP-AES has been used for the determination of rare earth elements (REE) in samples of phosphorite deposits collected from the Western Desert, Egypt. Complete dissolution of the samples was achieved by using acid digestion with HF/HNO3/HCl in a PTFE closed vessel and subsequent treatment with HClO4, with the same procedure but with fuming HCl replacing HClO4, and with HNO3 and fuming HCl in a quartz vessel and subsequent treatment with HF/HClO4/HNO3. Analysis lines for La, Ce, Pr, Nd, Sm, Gd, Dy and Y were selected after study of the spectral interferences for the sample types concerned. Results revealed that the average total content of the REE, which could be directly determined in the present samples, varies between 1.08 and 1.53 mg/g, whereas individual element concentrations range from 40 to 300-mu-g/g. Analysis results obtained with the different dissolution techniques were found to be in good agreement.