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

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)