RADIOCHEMICAL SEPARATION OF La$sup 140$ FROM Ba$sup 14$$sup 0$

An ion-exchange method for separating La/sup 140/ from Ba/sup 140/ was developed, so that carrier-free La/sup 140/ may be obtained in a pure state (ratio of La/sup 140/ disintegrations to Ba/sup 140/ dis0/!> 1.3 x 10/sup 4/. The coefficient of distribution of the two elements on resin using 0.5% citric acid-ammonium citrate buffer of pH 5.5 was found to be 1.28 x 10/sup 4/. Dowex- 50 resin in the ammonium form was found to retain Ba while the complex La citrate is eluted by the 0.5% solution. With a 8-mm dia column filled to a height of 15 cm, all the activity is collected in 50 ml of eluate with a slow flow rate (0.5 ml/min). The recovery yield of La/sup 140/ is better than 95%;, the first 3 elutions nt 1-week intervals give 100% yields but afterwards the yield diminishes. The purity of La at the moment of separation is indicated by the ratio of activity, 2.5 x 10/sup -6/. The amount of Ba in the eluate could be determined by separation with citrate buffer on an anionic column (Dowex 1 x 8). The recovery of Ba/sup 140/ from a BaLa carrier-free solution on such a column was 90-more » 95%, decontamination factor approximates 10/sup 5/. (TCO)« less