LANTHANUM 265 



Intake Levels. Lanthanum is one of the rare-earth group, and httle 

 or no information is available as to the naturally occurring levels in bio- 

 logical material. Since La'*" results from fission, there is an interest in 

 its behavior in the animal. There have been reports that yeast tends to 

 accumulate lanthanum, and this has been studied using the Ba'^^-La'*" 

 isotopes (La-1) (see references under Barium). 



Radioassay. Routine beta or gamma counting presents no particular 

 problem. 



Chemistry. Biological samples may be wet- or dry-ashed. It is some- 

 times necessary to separate the La'*" daughter from Ba'**^, and this can 

 be done as follows (La-2) : The BaCU solution into which the lanthanum 

 has grown is treated with FeCls and made basic with NH4OH, and the 

 Fe(OH):i is separated out and dissolved in HCl and reprecipitated twice 

 with NH4OH, Ba being added as a holdback carrier each time. The iron 

 in acid solution can finally be extracted with isopropyl ether to leave the 

 lanthanum in the aqueous phase. 



Typical Methods. About 5 ^lQ of purified La'*° obtained from Ba"° 

 (La-2) was injected intraperitoneally or intramuscularly into a rat. The 

 tissues were ashed at 500°C in porcelain, and the ash transferred to a por- 

 celain dish 4 cm in diameter. (3ne milliliter of H2O was added and evap- 

 orated in hot air. Weak samples were measured with an ll-mg/cm^ 

 end-window tube, and stronger samples with an electroscope. Self- 

 absorption curves using the La'*" in NaCl were established and used for 

 correction of samples. 



In a study of the effects of chelating agents on the distribution and 

 excretion of radioisotopes, a dose of 200 ;uc La'*" as the EDTA complex 

 was administered intravenously to a patient, and the urine collected by 

 catheter for radioassay (La-3). 



La-l. Bowen, V. T., and Ann C. Rubinson: Uptake of Lanthanimi by a Yeast, Nature, 



167: 1032 (1951). 

 La-2. Hamilton, Joseph G.: Metabolism of Fission Products (Progress Report for 



Month Ending March 15, 1943), MDDC-1142, Mar. 15, 1943. 

 La-3. Hart, Hiram, and Daniel Laszlo: Modification of the Distribution and Excretion 



of Radioisotopes by Chelating Agents, Science, 118: 24-25 (1953). 



