A comparison of combustion and low beta counting methods for the determination of low levels of¹⁴C activity in animal tissue

Abstract

Low β-counting was compared to combustion and liquid scintillation counting for detection of low levels of¹⁴C activity in animal tissues. In two separate experiments tissues from sheep and from pigs were analyzed. The first experiment utilized tissues from sheep into which a known amount of¹⁴C radioactivity was added. Combustion analysis gave somewhat higher recovery than low β-analysis, 92.8% compared to 85.7%. Statistical analysis indicated that the greatest source of random variation was in sampling. In the second experiment tissues from pigs given a¹⁴C labeled drug were analyzed. Sampling was again the greatest source of random error, however, it was greatly reduced over that in the first experiment. This was attributed to higher levels of radioactivity or to more homogeneous incorporation of radioactivity into tissues. The analytical performance of the two methods was essentially the same and a decision as to the best method for tissue residue studies is dependent on other considerations.