Effect of Fiber Diameter in the Liquid Scintillation Counting of Wool Labeled by Reaction with [2-3H] and [2-14C] Iodoacetic Acid

Abstract

Wool samples were labeled by reaction with aqueous solutions containing [2-¹⁴C] iodo acetic acid or [2-³H] iodoacetic acid. The counting rate of each sample was measured, firstly, with the 'wool suspended in a liquid scintillation solution (direct method) and, secondly, after oxidizing the same sample and dissolving the products in another liquid scintillation solution. The counting rate determined by the direct method depended on fiber diameter, because of self-absorption of β-particies by the wool, whereas the counting efficiency of the oxidation method was constant. The ratio of the counting rates, direct/ oxidized, for ¹⁴C-labeled samples decreased linearly from 1.30 to 0.96 as the mean diameter increased from 14 to 35 μ. With ³H-labeled wool, the inverse ratio, oxidized/ direct, increased linearly from approximately 5.5 to 10.5 with increase in diameter from 14 to 35 μ.

It was also shown that wool samples may be labeled with a known amount of ¹⁴C by reaction with [2-¹⁴C] iodoacetic acid dissolved in a liquid scintillation solution. The results, which show that the reaction occurred uniformly through the fiber, provide the basis for a new method of measuring mean fiber diameter.