No abstract

A liquid chromatographic method for the determination of triadimefon (Bayleton™) in triadimefon technical and formulated products has been developed and subjected to a collaborative study with 7 participating collaborators. Formulations were extracted with mobile solvent and analyzed by normal phase chromatography, with 4-chlorophenyl sulfoxide as an internal standard. Collaborators were furnished with standards and samples of technical products, 50% wettable powders, and 25% wettable powders for analysis. Coefficients of variation of the values obtained on these samples were 1.42, 0.82, and 1.05%, respectively. The method has been adopted official first action.

The analysis of trichlorfon by direct gas chromatography is discussed. A procedure is described for the determination of impurities in trichlorfon by using a fused silica capillary column and cold on-column injection. Attempts at quantitating trichlorfon using this system were unsuccessful due to problems with irreproducibility of the peak area. Although no derivatization was performed, there was no decomposition of the analyte as confirmed by mass spectrometry

Chromatography, thermal methods, and other associated physical determinations have been applied to the assignment of purities to standard reference materials. Each of these techniques has limitations, and each generally requires a primary standard of known purity. The establishment of purities on organophosphorus compounds can easily be performed without the availability of a typical primary standard by using proton decoupled 31P FT-NMR comparison to surrogate materials of known purity. A proposed analytical standard reference material of oxydemeton-methyl was evaluated using a 7.3 Tesla FT-NMR (300 MHz proton) using inverse-gated WALTZ decoupling. The resulting phosphorus singlet was compared with that of trlmethyl phosphate. This technique for purity assignment was confirmed by 2 additional experiments: (1) comparison of an established standard and a blind sample of demeton-S-methyl (Metasystox-I®) , with trlmethyl phosphate and (2) comparison of an established standard of disulfoton (Dl-Syston®) vs 0,0,0-trimethyl phosphorothloate.

A liquid chromatographic method for determination of azinphosmethyl (Guthion®) in formulated products has been developed. Samples are dissolved in acetonitrile and analyzed by reverse-phase chromatography using n-butyrophenone as an internal standard. The method was subjected to a collaborative study involving 15 participating laboratories. Each collaborator was furnished with reference standard, internal standard, and blind duplicate samples of Guthion 50% wettable powder (50WP), 3 flowable (3F), and emulsifiable concentrate (2L and 2S) formulations. Collaborators were instructed to evaluate the method by peak height measurements only. Relative standard deviations for reproducibility (RSDR) were 1.11, 6.28, 2.47, and 1.17% for the 50WP, 3F, 2L, and 2S formulations, respectively. The method has been approved interim official first action for determination of azinphos-methyl in the 50WP, 2L, and 2S formulations.