2-Trichloromethylbenzimidazole,a new selective chromogenic reagent for detection of some heteroaromatic pesticides on thin-layer chromatographic plates

A highly selective method for the detection of several pesticides containing a heteroaromatic ring in the molecule (e.g. nicotine, pyrifenox or prochloraz) on thin-layer chromatographic (TLC) plates is described. The necessary detection condition is the presence in the ring of at least one tertiary nitrogen atom without substitutents on the two adjacent carbon atoms and, in the case of azoles, the protection of a secondary NH group by an alkyl or acyl group. The detection is realized by spraying the developed chromatogram with an acetone solution of 2-trichloromethylbenzimidazole and subsequently heating at 100-150°C in a drier. The detection limit is 20 ng to 10 μg depending on the detected compound. Some pesticide formulations may be analyzed using this method.