Terbuthylazine technical and its 80% wettable powder were analyzed in a CIPAC collaborative study. The content and the identity were determined by gas-liquid chromatography on a column of 3% Carbowax K20M on Gas-Chrom Q, using di-n-pentylphthalate as the internal standard. Results obtained from 27 government, university, and industrial collaborators showed within-laboratory repeatability of 1.3% for the technical and 1.0% for the wettable powder. Reproducibility was 2.1% for both samples. The method has been adopted official first action
Chloroxuron technical and its 50% wettable powder were analyzed by 17 participants in a CIPAC collaborative study. The analytical method used involves acid extraction to remove interfering free amines, followed by alkaline hydrolysis of the extraction residue, distillation, and titration of the liberated dimethylamine. Related byproducts which may interfere are determined by semiquantitative thin layer chromatography. Results obtained from 17 government and industrial collaborators showed good repeatability within laboratories. Good agreement was also achieved between laboratories. A reproducibility of about 1.5% was obtained. The method has been adopted as an interim official CIPAC-AOAC method.
Chlorotoluron technical and its 80% wettable powder were analyzed by 19 participants in a collaborative study. The analytical method used involves acid extraction to remove interfering free amines, followed by alkaline hydrolysis of the extraction residue, distillation, and titration of the liberated dimethylamine. Related by-products which may interfere are determined by semiquantitative thin layer chromatography. Results obtained from 19 government and industrial collaborators showed good repeatability within laboratories. Good agreement was also achieved between laboratories. An overall coefficient of variation of about 0.8% was obtained. In 1974 the analytical method was accepted as a full CIPAC method. In 1975, the method was adopted as an official first action AOAC method.
A simple method for measuring captan was tested by 18 collaborators. Formulations are extracted with methylene chloride which contains diethyl phthalate as an internal standard, and detected at 254 nm after high pressure liquid chromatographic separation in a 25 cm × 4 mm column packed with 10 µm silica gel. After inert materials are removed, the supernate is added directly to the column with methylene chloride as the mobile phase; peak height ratios are used for quantitation. Most pesticides commonly formulated with captan do not interfere. Retention times and UV response factors relative to captan are listed for 34 pesticides formulated with captan. The collaborators made single determinations on 6 samples (3 pairs of duplicates). The coefficients of variation were 0.67% for the technical, 1.16% for the 50% wettable powder, and 1.71% for the 5% dust. Several collaborators were unable to separate carbaryl and diethyl phthalate on a combination dust containing captan, dicofol and carbaryl; therefore, the method has been adopted as official first action only for captan formulations containing no other active ingredients.
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