Application of 2-Trichloromethylbenzimidazole in Analytical Chemistry : A Highly Selective Chromogenic Reagent for Thin-Layer Chromatography and Some Other Analytical Uses

Abstract EN

2-Trichloromethylbenzimidazole (TCMB) was used as a chromogenic reagent in organic or inorganic analysis, mainly in thin-layer chromatography (TLC).

In reactions of TCMB with some heteroaromatic nitrogen containing compounds, such as azines, azoles and benzazoles, a formation of high colored products occurred.

For azines, the chromogenic reaction was highly regioselective, since the both adjacent α-positions versus the nitrogen atom(s) must not be substituted.

A TLC method of detection was developed.

Thirty azines, azoles, and benzazoles were detected at the detection limit 10 ng to 1 μg.

This method was also applied for detection of heteroaromatic pesticides, and the attempts to construct active and passive dosimeters for nicotine were made.

In a prechromatographic reaction of aromatic o-diamines with methyl trichloroacetimidate, TCMB or its derivatives were formed in situ.

Followed by TLC and visualization in pyridine vapors, this procedure was applied for detection of o-phenylenediamine derivatives.

The reaction product of TCMB and pyridine (LI Complex) was identified and fully characterized.

Two different reaction mechanisms: with electron deficient basic heteroaromatic compounds, like pyridine, and with more acidic compounds, for example, pyrrole, were discussed.

In aqueous solutions, the LI Complex may be also used as a new indicator for complexometric, adsorption and acid-base titration of inorganic compounds.