RADIOACTIVATION ANALYSIS 



421 



useful biological application of radioactivatioii analysis. These analyses 

 were performed using a neutron flux of 10^-'. Table 10-3 summarizes 

 typical results. Particularly noteworthy is the small sample that can be 

 used and yet give reliable values. The recoveries and reproducibility 

 were excellent in all cases. 



[Comjiiled from A. A. Smales and B. D. Pate, The Determination of Sub-microgram 

 Quantities of Arsenic by Radioactivation, II-III, Analyst, 77: 188-195, 196-202 



(1952).] 



It is pointed out that this method is more than a hundred times as sen- 

 sitive as the methods previously available. Although radioactivation 

 analysis for arsenic will not replace routine chemical methods, there may 

 be situations where the added sensitivity will be valuable. A limiting 

 factor in the sensitivity of most conventional methods is the presence in 

 reagents of trace amounts of the element to be determined. The proce- 

 dure for arsenic illustrates how the arsenic content of the reagents cannot 

 interfere with the analyses, since the reagents are not used until after the 

 irradiation. Another important point is that quantitative separations 

 are not required, since known amounts of carrier are added after irradia- 

 tion and a correction can be applied for losses from the measured chemical 

 yield. 



Sodium and Potassium. Cephalopod nerve fibers have been analyzed 

 for sodium, potassium, and chlorine employing radioactivation procedures 

 by Keynes and Lewis (20). Giant axons were dissected and, after having 

 been washed, weighed, and dried, were placed in transparent quartz tubes 

 about 3 cm long with an internal diameter of 2 mm. The tubes were then 

 sealed at both ends with an oxygen flame. These samples were irradiated 

 in the Harwell pile for 1 week in batches of 20. Three tubes each contain- 

 ing about 20 mg K2CO3, 3 mg Na2C03, and 1 mg KH2PO4 were placed 

 with each batch of sample tubes. 



After bombardment, each sample tube was broken open, and the nerve 

 transferred to a nickel dish containing a drop of K2C();i solution. The 



