In order to determine trace lanthanoids in geological and cosmochemical samples, an analytical procedure for radiochemical neutron activation analysis (RNAA) was developed, where lanthanoids are radio-chemically purified through precipitations of hydroxides and fluorides, and cation exchange using HBr as an eluent. Chemical yields are determined by reactivation. The procedure was applied to the Allende meteorite and geological standard rocks. Our data for Allende are in excellent agreement with literature values, and those values for standard rocks, JP-1 (peridotite) and JF-2 (feldspar), in which lanthanoids are depleted by orders of 1 to 2 compared with those in Allende, seem to be reasonable, although not properly evaluated because of large scatterings in their literature data. This suggests that the present RNAA procedure is highly effective in determining trace lanthanoids (less than 1 ng) in rock samples.
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