Improvements in detergency precision with radioactive soil

Abstract

Recent work on the use of seven-component, doubly labeled radioactive soil to evaluate deter-gency has depended on the analyses of the fabric for residual soil. Because of the variation of soil concentration within and between fabric swatches, considerable replication was required to lower the standard deviations to ±10%. A method for the analysis of wash water has been developed which requires much less replica-tion and achieves higher precision (<±2%). The method is based on the use of an inhomo-geneous scintillator, which can emulsify, or at least suspend, large volumes of water in a liquid scintillator while maintaining good counting efficiency. Studies of closure, i.e., amount of soil recovered in wash water plus fabric compared with soil introduced into the Tergotometer, have demonstrated that the method is reasonably accurate and quite precise.