The Measurement of Artificial Radioactivity in Liquid Tracer Samples Using C11

Abstract
Using C11 as tracer for the study of carbon dioxide absorption in plants, unexpected analytical difficulties were encountered. However, a satisfactory technique was developed for the rapid measurement of radioactivity in liquid samples. A degree of precision was obtained so that after the elapse of 6 half‐lives (2 hours) the sum of the activities taken from the reaction system was accurate to 1 or 2 percent. This required the determination of an accurate half‐life value for C11 (20.35 min.). The experimental procedures are described.