It was shown in the first part of this work' that carrier-free rare earths of the cerium sub-group can easily be separated from each other on a column filled with strongly basic anion exchange resin using aqeuous methanol solutions of neutral nitrates as an eluent. In the field of the preparative nuclear chemistry of the rare earth elements, however, one frequently also meets the necessity of separating microamounts of rare earths from macroamounts of adjacent rare earths. This necessity generally arises in solving of the following problems:
(I) preparation of very pure rare earth targets, (2) determination of rare earth impurities in rare earth samples, (3) separation of carrier-free nuclear reaction products from macroamounts of non-isotopic target.
Commercial rare earth proclucts, even the purest ones, always contain rare earth impurities. The quantity of these impurities, depending on the quality of the product, may amount to 10-100
,ug contaminant element/g rare earth product. Their presence is, in some cases, of no great importance. These may give rise, however, to serious difficulties when carrying out many nuclear reactions, e.g. in the performance of spallation reactions for nuclear spectroscopic measurements. The presence of impurities in individual rare earths in quantities much greater than IO pg makes it difficult to perform microchromatographic separations of the spallation rare earth proclucts and to prepare sources by means of electrolysis.
The control of target purity requires a reliable and sensitive analytical method. The majority of the present analytical methods are ba.sed upon the preliminary separation of the rare earth impurities from the contaminated sample and from one another. The separation of microamounts from each other can easily be carried out. Thus, the highly sensitive method of activation analysis, in general, does not raise any difficult separation problems. Moreover, the analysis, in some cases, can be carried out without any preliminary separation, merely using electronic measuring devices. However, with the use of less sensitive analytical methods (e.g. spectrophotometric methods) the quantity of the sample from which one has to separate microamounts of impurities is often as much as 1-2 g. In the analytical chemistry of the rare earth elements, the process of concentration of the impurities gives rise to the greatest difficulties, Similarly, processing of 2-3 g target quantities is also necessary in the preparation of neutron deficient rare earth isotopes for nuclear spectroscopic measurements.