Color sensors for indole vapors based on Ehrlich-type reactions.

A sensitive and simple color sensor for indole vapors has been developed based on the Ehrlich-type reaction in solid polymer film. Upon 60-min exposure of the film sensor to the air containing 5 - 100 ppb of indole vapors, pink or magenta color could be recognized by the naked eyes. Alternatively, a trial gas detector tube has been prepared by mixing the reagents with sea sand. When air (100 mL) was pumped through the detector tube, indole vapors above 20 ppb could be detected within 1 min. The sensing was selective to the vapors of indoles and pyrroles, and other VOCs or ambient moisture did not interfere.