Rapid Radiochemical Separations

Many of the separation techniques we have described take hours to perform. Many interesting nuclei, such as the heavier actinides, the transactinides, or the light nuclei used in PET studies, have much shorter half-lives. Thus, we will briefly review the principles of rapid radiochemical separations (procedures that take seconds to minutes) and refer the reader to Henman and Trautman (1982), Meyer and Henry (1979), Schadel et al. (1988), and Trautman (1995) for details. 

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In most chemical separation procedures, the goal is to selectively transfer the species of interest from one phase to another, leaving behind any unwanted species. The phase-to-phase transfer is rapid, but the procedures to place the species in the proper form for transfer to occlu are slow. The goal of rapid radiochemical separations is to speed up existing chemical procedrues or to use new, very fast chemical transformations. 

Two procedures are commonly used for rapid radiochemical separations, the batch approach and the continuous approach. In the batch approach, the desired activities are produced in a short irradiation, separated and counted with the procedure being repeated many times to reduce the statistical uncertainty in the data. In the continuous approach, the production of the active species is carried out continuously, and the species is isolated and counted as produced. 

Neutron activation analysis (NAA) with a rapid radiochemical separation has been the method generally used in recent years, but requires substantial investment, has high operating cost and limited availability. Modem flameless atomic absorption (AAS) instruments provide sensitivity approaching that of NAA and offer a viable alternative for the detection of firearms discharge residue. 

This volume which deals with rapid radiochemical separations Is the fourth In a series of monographs on radiochemical techniques which will parallel the series on the radiochemistry of the elements. The same general style Is used in both series of monographs, Including general reviews of the technique, discussions of the principles involved, a detailed survey of applications to different systems, and a collection of selected procedures which use this technique as reported in the literature. 

This second series of techniques monographs will cover a number of radiochemical techniques which have not been reviewed elsewhere. Plans include revision of these monographs periodically as new information and procedures warrant. The reader is therefore encouraged to call to the attention of the authors any published or unpublished material on rapid radiochemical separations which might be included in a revised version of the monograph. 

For short-lived radionuclides the time required for separation Is a very important factor and should be made as short as possible. In this monograph the term "rapid radiochemical separation" Is limited to techniques required to separate radionuclides which have half-lives of less than 20 minutes. An effort has been made to collect from the literature as many practical examples of such techniques as possible. 

This monograph Is arranged In three main sections. A short section (i) describes general procedures used to prepare samples for rapid radiochemical separation. Then the separations reported In the literature have been categorized In two different ways. In section II the procedures have been arranged by type of process, such as recoil, distillation, solvent extraction, etc. In each subsection there are given typical examples of different kinds of techniques reported — but the sections are not necessarily exhaustive. 

I. GENERAL PROCEDURE PRIOR TO RAPID RADIOCHEMICAL SEPARATION A. Target Material... 

Chelate extraction systems have also had very extensive application in rapid radiochemical separations. 

Many other extraction methods used In chemical analysis could undoubtedly be readily applied to rapid radiochemical separations. ... 

Precipitation techniques used in chemical analyses also have many applications in rapid radiochemical separations. Although this method tends to have some disadvantages, such as time consumed in filtration or washing and the coprecipitation of undeslred impurities, it can still be very valuable, expecially when other rapid separation methods are not applicable. 

Recent reports describe the successful application of this technique to the separation of Zn in reactor effluent (233), rapid radiochemical separation of cadmium activity In fission products (63), and the radiochemical separation of Indium (217) ... 

Kusaka Yu, Meinke WW (1961) Rapid radiochemical separations. Report NAS-NS 3104. Nat Acad Sci, Washington... 

H. Persson, G. Skarnemark, M. SkAlberg, J. Alstad, J. O. Liuenzin, G. Bauer, F. Haberberger, N. Kaffrell, J. Rogowski and N. Trautmann, SIS AK-3. An Improved System for Rapid Radiochemical Separations by Solvent Extraction, Radiochim. Acta 48 (1989) 177. 

Kusaka, Y. and Meinke, W. W. 1961. Rapid Radiochemical Separations. National Research Council Report NAS-NS 3104. Washington, DC National Research Council. 

Some investigators are finding activation analysis a useful method to determine trace elements, either in essential or nutrient forms or as contaminants, in various food products. Das et al. (217) have shown that many dairy products contain only nanogram amounts of Mn. Hingorani and Chandrasekaran (401), Moeller and Leddicotte (620) and Samuelsson (814) have determined the strontium content of activated milk by radiochemical separations. Molinski, el al. (623) used a rapid radiochemical separation method to determine nanogram concentrations of V in milk powder. Samuelsson (813) also determined submicrogram amoimts of copper in whole milk by activation analysis and Allaway and Cary (12) developed an activation analysis method to determine 0.1 ppm of Se in dried skim milk. 

Persson, H., Skarnemark, G., Skalberg, M., Alstad, J., Liljenzin, J.O., Bauer, G., Haberberger, F., Kaffrell, N., Rogowski, J., Trautmann, N. SISAK3—an improved system for rapid radiochemical separations by solvent extraction. Radiochim. Acta 48, 177-180 (1989)... 

Herrmann, G. Rapid Radiochemical Separations for the Study of Short-... 

Rapid Radiochemical Separations, NAS-NS-3104 [ 1961 ]. 6.00 Separations by Solvent Extraction with Trl-n-octylphosphine Oxide, NAS-NS-3102... 

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