Ultraviolet Spectrophotometric Method for Ronnel in Feeds

Abstract The ultraviolet spectrophotometric method for Ronnel in feed mixtures, presented at the 1963 AOAC meeting, was studied further at levels of 0.015–0.6% Ronnel by 10 collaborators to test the accuracy and reproducibility of the method by vising reagents free from abnormal ultraviolet absorbance. The variety of feed ingredients was increased to include milo, barley, and alfalfa in addition to those used in the 1963 study. Ronnel is extracted from the sample with methanol-petroleum ether and hydrolyzed to the 2,4,5-trichlorophenate. After solvent evaporation, the residue is dissolved in water, the pH is adjusted and buffered at 7.0, calcium chloride solution is added, and the mixture is steam distilled. The 2,4,5-trichlorophenol in the steam distillate is extracted with iso-octane and measured spectrophotometrically. All collaborators obtained good results; therefore, the Associate Referee recommends that the method be adopted as official, first action. Experimental studies showed that 2,4,5-trichlorophenol can be separated from Ronnel by ion exchange. This will be studied collaboratively next year.