Direct Liquid Scintillation Radioassay of14C-Labeled Herbicides in Soil

Abstract

A liquid scintillation counting solution was developed which optimized the direct assay efficiencies of14C-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3,6-dichloro-o-anisic acid (dicamba), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) in soil. In this counting technique, 3-g soil samples containing14C-labeled herbicide were placed directly into a liquid scintillation vial containing a phosphorescent counting solution. Samples were shaken and allowed to settle before assaying using a liquid scintillation spectrometer. This direct radioassay was as efficient or more efficient than double or single extraction processes. Automatic external standardization in conjunction with the liquid scintillation counter was an effective tool for estimating the14C present in soil samples.