Developed spectrophotometric method for thorium determination in different Rosetta monazite concentrates using thorin dye

A developed, sensitive and direct spectrophotometric determination of leached thorium from different Rosetta monazite concentrates using thorin dye was studied for optimum thorium determination using thorin dye. Leached thorium was determined without prior separation using either solvent extraction or ion exchange techniques. Optimization of pH of different mineral acids, buffer pH, dye concentration and thorium concentration were studied for optimum thorium determination. After three leaching steps of thorium from monazite using 10M HNO3, solid to liquid (acid) ratio 1:60, two hours stirring at 60oC, the percentage leaching of thorium was 98.9%. Interference due to traces of rare earths was overcome using 3% H2O2. Beer’s law was obeyed from 0.1µg ml-1 to 100 µg ml-1 with molar absorptivity (?) value 0.173x104 mol-1cm-1 and standard deviation 0.133. The % RSD for 10 replicate measurements of 4ppm thorium was 1.48%.