Insecticide-retentive carriers. 1. Methods of analysis

Abstract

Clay-based carriers of insecticides or 'dusts', e.g. talc or bentonite impregnated with fenitrothion, may either retain the protectant after admixture with wheat or release it into the surrounding grain. The amount of carrier was determined by mixing wheat with water or ethanol, subjecting to ultrasound, and determining absorbance of the supernatant at 580 nm. Swirling in water under ultrasound followed by decanting removed more than 90% of 9 tested carriers from water, was more efficient than sieving, and had no effect on fenitrothion levels in wheat that had previously been sprayed with an emulsifiable concentrate formulation. The amount of fenitrothion retained was measured by 3 methods, each duplicated, and was 0.5-5% for talc, 98-103% for Nuchart-Attaclay, 565-80% for Halloysite, and 96-97% for Steecoben.