NICKEL 273 



Nickel 63 (85 yr) Beta 0.003 Gamma 



("at. No. Sp. Act. Form Cost Chem. Cant. Radiochem. Cont. 



Ni-63-I 0.35 mc/g ^letal $33/3.5 mc — ~1 mc Ni^s (8 X 10^ yr) 



Ni-63-P 5-50 mc/g NiCU $45/mc — ~0.01 % Nif-^ 



}fica W. Int. C. Scint. C. 



5 X 10-2 2.6 X 10-" 1.4 



Critical Onj. 

 Liver 



Intake Levels. Nickel is found in almost all biological materials, 

 although, so far as is known, it is not essential for plants or animals. A 

 normal low intake for man has been reported as 0.3 to 0.5 mg daily (Ni-1). 

 Some typical values for tissues on a fresh basis are as follows: human liver, 

 0.09 ppm; human pancreas, 0.04 ppm; ox liver, 0.125 ppm; ox pancreas, 

 0.135 ppm; cow's milk, 0.004 ppm; egg yolk, 0.02 ppm; and fish, 0.015 

 ppm (Ni-1). Crop plants range from about 0.15 to 4 ppm on a dry basis, 

 with an average of about 0.9 ppm. A recommended nutrient solution 

 for plants contains about 0.01 ppm. Oral doses of 10 to 20 mg/kg pro- 

 duced no symptoms in dogs, but 22 to 44 mg/kg caused vomiting and 

 diarrhea. The toxicity is much higher when given intravenously; 7 to 

 8 mg/kg of nickel sodium citrate was fatal to rabbits and dogs (Ni-1). 

 Rats will tolerate doses of 10 mg/kg of the nickel sodium citrate sub- 

 cutaneously, whereas only 1 mg/kg appears to be tolerated intravenously 

 with any degree of safety; this latter applies for the chloride also (Ni-2). 



Radioassay. Preparation Ni-63-P will probably be the one of choice, 

 although the high cost should be noted. The extremely low beta energy 

 of Ni^^ has made the counting measurement very difficult and has dis- 

 couraged the use of this radioisotope. The Ni^^ radiocontamination 

 does not present any particular problem. For counting, it will be essen- 

 tial that the nickel be separated from as much extraneous material as 

 possible in order to eliminate serious sensitivity losses from self-absorp- 

 tion. The removal of nickel from the sample may be accomphshed either 

 by chemical separation procedures employing dimethylglyoxime or by 

 electroplating. The latter method has proved the more satisfactory, and 

 a procedure has been developed in which the sample is ashed in the muffle 

 furnace, the ash taken up in concentrated H2SO4, and the entire solution 

 or an aHquot put into electroplating solution (100 g ammonium sulfate, 

 180 ml concentrated ammonium hydroxide, and 5 g ammonium hypo- 

 phosphite per hter). The nickel is then electroplated in the presence of 

 inert carrier, preferably with the use of a controlled-cathode electroplating 

 device (Ni-2). For measurement, the internal counter will be the instru- 

 ment of choice on account of the much higher sen.sitivity. 



