322 ZIRCONIUM 



Zirconium 95 (65 days) Beta 0.4, 0.887 Gamma 0.708 



Cat No Sp Art Form Cost Chem. Cont. Radiochem. Cont. 



Zr-95-I 0.05 mc/g Zr(0H)4 $12/0.06 mc - 0.1 mc Zr«M17 hr) 



Nb^5 daughter (35 days) 



Rf/vic 

 4 



Zirconium 95 (65 days) Beta 0.4, 0.887 C.amma 0.708 



Niobium 95 (35 days) Beta 0.146 Gamma 0.758 



Cat No Sp Art Form Cost Chem. Cont. Radiochem. Cont. 



ZrNb-95-P CF Oxalate Sl/mc — Nb^^ daughter (35 days) 



complex 



Intake Levels. Zirconium is not an important naturally occurring 

 constituent of biological materials. Of interest has been its use to 

 increase the removal of bone-seeking radioisotopes from the body, as well 

 as the possibiUties of using radiocolloids of zirconium for therapeutic 

 irradiation. The acute oral LD50 values for rats for five zirconium salts 

 ranged from 990 to 2290 mg/kg, indicating a relatively low toxicity (Zr-1). 

 The intraperitoneal LD50 values were 63 to 939 mg/kg, zirconyl sulfate 

 being the least toxic and zirconium sulfate the most toxic. 



Radioassay. The primary difficulty in the use of Zr^^ as a tracer 

 results from the relatively long-lived Nb«^ daughter. At equilibrium the 

 Zr^VNb^^ ratio is 0.465. It requires a waiting period of 6 months to 1 yr 

 after the sample has been taken from the biological system to permit the 

 attainment of equihbrium between Zr«^ and Nb^^ For short-term experi- 

 m-ents, preparation Zr-95-I containing small amounts of Nb^^ might be 

 used before appreciable growth of Nb«^ has occurred. Other methods 

 might involve the double assay of the two activities in the samples by 

 differential beta-absorption measurements or by separations such as ion 

 exchange or filter-paper chromatography. In a distribution study of Zr 

 colloids in the rabbit, it was shown that the Nb^^ had the same metabohc 

 behavior as did the Zr^^ (Zr-2). Routine beta or gamma counting is 



satisfactory. • j ix/r u ^ 



Chemistry. Biological material may be wet- or dry-ashed. Methods 

 are not available for chemical estimation of traces of zirconium in plant 

 or animal tissues. For separation of zirconium, the insoluble zirconium 

 phosphate or barium fluozirconate is used (Zr-3). Attention is called to 

 the possibility of aggregate formation in dosing solutions, since precipita- 

 tion of a hydroxide or basic salt will take place from a dilute solution 

 of a simple salt at pH 2. The colloidal properties may be minimized 

 by the use of a httle oxalic or hydrofluoric acid or by citric acid at 

 pH4. 



