PRINCIPLES OF TRACER METHODOLOGY 



21 



u. 



c 

 o 







100 



200 



400 



500 



600 



Fig. 



300 

 Time t 



1-2. Simple removal from one phase. Exponential removal of injected labeled 



min 



ferric /3-globiilinate from plasma of man. [From Louis B. Flexner, Dean B. Cotvie, and 

 Gilbert J. Voshurgh, Studies on Capillary Permeability with Tracer Substances, in 

 "Biological Applications of Tracer Elements," Cold Spring Harbor Symposia Quant. 

 Biol, 13: 88-98 (1948).] 



atom may have any value from zero to infinity. It can be shown that 

 the average life = 1/k. 



If two isotopes of different half-lives are present, the decay curve will 

 be a composite one. If the half-lives are sufficiently different, it is pos- 

 sible to analyze the composite curve graphically to estimate the half-life 

 of each component and the proportions of each component present. This 



