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2745177 
Technical Report 
Gas chromatographic determination of technical pyrazon (5-amino-4-chloro-2-phenyl-3 (2H) pyridazinone) 
Vyboh, P; Michalek, M; Sustek, J; Batora, V 
1974 
PESTAB/75/0481 
Sci 
2 
PESTAB. 5-Amino-4-chloro-2-phenyl-3(2H)pyridazinone (common name pyrazon) is the active ingredient of herbicide formulations known under the trade names Burex, Chlorazine, Pyramina, and Phenazon. Pyrazon content was evaluated using the internal standard 4-chloro-5-methylamino-2-phenyl-3(2H)pyradazinone. The FID detector and a glass column (50 X 0. 25 cm) packed with 2% cyclohexane-di-methanol succinate on silanized Chromosorb G(80-100 mesh) were used. Technical products can contain two interesting impurities, the non-active pyrazon isomer 4-amino-5-chloro-2-phenyl-3(2H)pyridazinone, and the unreacted 4,5-dichloro-2-phenyl-3(2H)pyridazinone, the latter of which is significant from the point of view of toxicology. Determination of these two compounds under the conditions used for pyrazon is practically impossible. They were therefore determined on a separate glass column (70 X 0. 24 cm) packed with 5% cyclohexane-di-methanol succinate on Chromosorb G (60-80 mesh). A standard addition method for small concentrations of 4,5-dichloro-2-phenyl-3(2H)pyridazinone in technical pyrazon products is also described. (Author abstract by permission)