A NEW RA-BA CHROMATOGRAPHIC-SEPARATION AND ITS APPLICATION TO RA MASS-SPECTROMETRIC MEASUREMENTS IN VOLCANIC-ROCKS

We have adapted the recent chromatographic method described by E.P. Horwitz and coworkers for Sr separation, to perform an efficient Ba-Ra separation for measuring Ra isotopes in volcanic rocks by mass spectrometry. Extraction chromatography is used with a solution of a crown ether (4,4'(5')bis-(tert.-butylcyclohexano)-18-crown-6) in 1-octanol, adsorbed on an inert substrate as an extractant. The ElChrom Company markets this resin under the name Sr Spec(R). We show that this technique gives a very efficient Ba-Ra separation which compares favourably with previous chromatographic methods. The chemical and mass-spectrometric procedure is described in detail and is applied to Ra measurements in volcanic rocks.