FREE AMINO ACIDS OF BLOOD AND URINE 261 
This method appears suitable for the counting of chromatographic effluents and 
almost all biological substances which may be brought into solution in an acid, 
neutral or alkaline aqueous medium. 
Insoluble biological materials (tissues) may also be counted after mineralization. 
Carbon dioxide may be counted after trapping in sodium hydroxide. 
When using a fast electronic circuit and unselected E.M.I. photomultipliers 
(9514 S) the efficiency attained with the finer anthracene powder is 2° for tritium 
and 55%, for “C. The corresponding background amounts to 60 counts/min when 
operating at room temperature. 
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