424 RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



amounts of strontium carbonate were used as standards (7). The irra- 

 diated tissue sample was dissolved in concentrated nitric acid, and a 

 standard amount of strontium carrier plus barium, iron, and copper hold- 

 back carriers was added. Strontium and barium nitrates were twice pre- 

 cipitated from strong acid solution, the precipitate dissolved in water, 

 additional iron holdback carrier added, and the iron precipitated with 

 ammonium hydroxide. The barium was separated from strontium as 

 the chromate in buffered acetic acid solution. The filtrate was made 

 shghtly ammoniacal, and the strontium precipitated as the oxalate, which 

 was dried, weighed, and counted with a scintillation counter. Table 10-6 

 shows the agreement obtained between replicates of the same sample. 



Table 10-6. Reproducibility of Strontium Determinations in Animal 

 Tissues by Radioactivation Analysis 



Sample No. Strontium, ppm 



1 5.6, 5.9, 6.1, 6.1 



2 14.4, 13.6, 14.4, 13.0 



3 33.2,-34.1,31.0,31.1 



4 44.8, 45.6, 45.9, 45.4 



5 56.1, 58.5, 55.8 



6 42.2, 45.7, 44.3 



(From W. A. Brooksbank, G. W. Leddicotte, and H. A. Mahlman, Analysis for 

 Trace Impurities by Neutron Activation, ORNL-CF-53- 10-52, Oct. 23, 1953.) 



Rare Earths. Brooksbank and Leddicotte (22) have described the use 

 of radioactivation and ion-exchange procedures to estimate rare-earth 

 elements in bone. After irradiation, cerium and lanthanum carrier was 

 added to a hydrochloric acid and nitric acid solution of the sample. The 

 rare earths were precipitated with sodium hydroxide, dissolved, and 

 reprecipitated in hydrofluoric acid. The fluoride precipitate was washed 

 and dissolved, and the rare earths precipitated again as the hydroxides, 

 which were dissolved and put on a small Dowex-50 column to separate the 

 lanthanum. The rare earths in the remaining fraction were precipitated 



T.^BLE 10.7. Determination of Rare Earths in Bone by Radioactivation 

 Analysis and Ion-exchange Separation 



Concentration, Concentration, 



Element ppm Element ppm 



Lanthanum 0. 27 Holmium 0.50 



Samarium . 009 Erbium 2 . 20 



Europium 0. 20 Thulium 1 . 30 



Gadohnium Ytterbium 1 .30 



Terbium 0. 0004 Lutetium 0. 08 



Dysprosium 0.00 Yttrium 0.04 



(From W. A. Brooksbank, G. W. Leddicotte, and H. A. Mahlman, Analysis for 

 Trace Impurities by Neutron ,\ctivation, ORNL-CF-53- 10-52, Oct. 23 1953.^ 



