The gas-liquid chromatographic determination of tetradifon technical and formulations was collaboratively studied in duplicate with 12 laboratories. Six samples were dissolved in dichloroethane with n-hexacosane as the internal standard, chromatographed on a column of 3% SE-52, and detected by flame ionization. The average coefficients of variation were 1.2% for the 2 technical samples, 1.6% for the 2 wettable powders, and 1.5% for the 2 emulsifiable concentrates. The method has been adopted official first action.
Diflubenzuron 90% pre-concentrate and its 25% water-dispersible powder were analyzed by a high performance liquid chromatographic method. Six samples were extracted with 1,4-dioxane, linuron was added as internal standard, and diflubenzuron was separated on a 25 cm × 4.6 mm column packed with Zorbax BP-C8 with acetonitrile-water-l,4-dioxane (450 + 450 + 100) at 1.3 mL/min and monitored at 254 nm. Results were obtained from 17 laboratories. Within-laboratory repeatability was 0.6% for both the pre-concentrate and the water-dispersible powder samples and the reproducibility was 1.2%. The method has been adopted as a full CIPAC method and was adopted official first action by AOAC.
A gas-liquid chromatographic (GLC) method is described for determining fentin acetate and fentin hydroxide in formulations in the presence of maneb. Triphenyltin acetate or hydroxide is converted to butyltriphenyltin by the Grignard reaction; the product is determined by GLC, using flame ionization or thermal conductivity detection, a column containing 5% SE-30 on Chromosorb W (HP) or Gas-Chrom Q, and docosane as the internal standard. Fifteen laboratories tested the method on 6 samples. The estimated repeatabilities expressed as coefficients of variation, ranged from 0.8 to 1.4% and the estimated reproducibilities from 1.3 to 1.7%.
A gas-liquid chromatographic method for determining dichlobenil in technical material and formulations was collaboratively studied by 7 laboratories. Five samples were chromatographed on a 10% Carbowax 20M column with methyl myristate as the internal standard and flame ionization detection. The estimates of the repeatability (different analysts) and the reproducibility, expressed as coefficients of variation, were, respectively, 0.8 and 1.0% for the technical sample, 1.4 and 1.7% for the wettable powder, and 3.5 and 4.6% for the granular formulations. This method was adopted as a full CIPAC-AOAC method.
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