A Liquid Scintillation Counting Technique for the Determination of the Mean Fiber Diameter of Wool Samples Labeled with [14C] Formic Acid

Abstract

A simple method of labeling wool in vitro with a known amount of ¹⁴C has been developed. Accurately measured volumes of a liquid scintillation solution, containing a small proportion of [¹⁴C] formic acid, were added to the wool samples in counting vials. After the formic acid had been absorbed by the wool, the counting rates of such samples depended on mean fiber diameter and on the degree of quenching of the scintillations. When the counter was operated at the appropriate ("balance-point") settings for each series of samples with the same degree of quenching, the counting rate fell linearly with increasing mean fiber diameter. Although the fall in counting rate was small— approximately 1% for a 1-μ increase in diameter—the results indicate that the accuracy of the method is sufficiently high to provide a new rapid method of measuring mean fiber diameter of large numbers of samples. An important advantage of the method is that the counting rate at the balance-point is independent of the presence of small amounts of vegetable matter. When vegetable matter is absent, the degree of quenching, which is measured simultaneously, is probably closely related to the yellowness of the wool and may, therefore, provide a useful index of this property.