Collaborative Study of Methods for Determination of Ronnel in Feeds and Mineral Mixtures

Abstract A GLC method (electron capture detector) for ronnel in cattle feeds at the 0.040% level and a UV method for ronnel in mineral mixtures (1–40% ronnel) were studied by 9 collaborators. Ronnel is extracted from feed by shaking with acetone, followed by direct GLC measurement. The method is simple and rapid and the electron capture detector is much more sensitive and gives cleaner ronnel measurements than the flame ionization detector used last year. Agreement between laboratories was good; coefficients of variation were 7.7, 7.1, 11.1% with ronnel recoveries of 95–100%. Analyses of feed samples after storage (several months) showed decreases in ronnel, found to be due to partial ronnel binding. Ronnel is extracted from minerals with methanol, followed by UV measurement. The coefficient of variation was 5.4%. The Associate Referee recommends that the mineral method be adopted as official final action and that the feed method be continued as official first action for 1 more year. An investigation of the binding effect is continuing.