Separation of Strontium-90 from Calcium

ONE of the main difficulties in determining the strontium-90 content of biological materials such as milk, bone and coral is the separation of strontium from the large amounts of calcium which accompany it. In an endeavour to avoid the rather tedious and time-consuming method based on the insolubility of strontium salts in strong nitric acid 1 , various ion-exchange methods have been developed 2–5 in which the alkaline earth ions have first been absorbed on to a cation exchange resin and then successively eluted by agents such as lactate and citrate at a controlled p H. Although the amount of strontium in such samples is very small, these methods require the use of a relatively large column of sufficient exchange capacity to absorb at least part of the accompanying calcium as well as the strontium.