Abstract
The focusing chromatography separation of radioactive alkaline earth and rare earth elements with potassium fluoride as a precipitation reagent was investigated. The experiments have been carried out with hydrochloric acid contained in the positive electrode cell and with a dilute aqueous solution of potassium fluoride contained in the nagative electrode cell. Fundamental factors such as the duration of the electrophoresis, pH value, the concentrations of the potassium fluoride solution and the hydrochloric acid, etc. were examined.
The sample solutions were 0.01 M hydrochloric acid containing a tracer amount of either barium-140 (containing lanthanum-140), strontium-90 (containing yttrium-90) or cerium-144(containing praseodymium-144). Each of these nuclides was carrier free, and the activity of each solution was 1 μ Ci/ml. The separated radioactive bands on the paper chromatogram were located by autoradiography. According to the detected positions, the filter paper was cut into pieces and the species of the radionuclides were determined by γ-ray spectrometry and the measurements of the energies and the half-lives of β-rays.
The present method gave good results for focusing and separating cerium-144, barium-140 or strontium-90 from the daughter nuclides, praseodymium-144, lanthanum-140 or yttrium-90, respectively. Moreover, this procedure was effective for the separation of alkaline earth group from rare earth group. The optimum separation was obtained by using 0.05 M hydrochloric acid in the positive cell, 0.05 M solution of potassium fluoride(buffered with sodium acetate) in the negative cell, the pH of which was 5.25.7, intensity of the electric field being 500 V/26 cm and migration time being 10 minutes. The mechanism of separation was thought to be as follows.
On the electrophoretic paper strip, the metal ions in the sample migrate into the potassium fluoride solution fed by the negative cell until the product of concentration of each metal ion and that of fluoride reaches its solubility product, so that position of the deposited fluorides on the paper strip are determined by their solubility products and their mutual separation is more effective.
