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Analysis of sulfonylurea herbicides by gas-liquid chromatography. 1. Formation of thermostable derivatives of chlorsulfuron and metsulfuron-methyl

Klaffenbach, P., Holland, P.T., Lauren, D.R.
Journal of agricultural and food chemistry 1993 v.41 no.3 pp. 388-398
heat stability, metsulfuron, methylation, chlorsulfuron, high performance liquid chromatography, gas chromatography
A method is described to overcome the thermal instability of sulfonylurea herbicides and thus enable their analysis by gas chromatography (GC). Methylation of chlorsulfuron by diazomethane in a variety of solvents usually yielded N-methylchlorsulfuron as the predominant product. This derivative was not stable to GC conditions, forming the N-methylsulfonamide. With diazomethane in either acetone or ethyl acetate and with longer reaction times substantial quantities of the N,N'-dimethyl derivatives of chlorsulfuron and metsulfuron-methyl were formed, which were characterized by GC-MS (EI and CI). These derivatives were thermostable and gave symmetrical GC peaks with good responses to both electron capture and nitrogen-phosphorus detectors. Reaction conditions were optimized in ethyl acetate to maximize yields of the N,N'-dimethyl derivatives. Formation of the derivatives was shown to be linear over the range 0.1-10 micrograms, and they were suitable for determination at residue levels.