Development of a monitoring tape for ammonia gas in air by fluorescence detection

Abstract

A porous cellulose tape impregnated with a processing solution that includes Eosine Bluish, p-toluenesulfonic acid, glycerin and methanol is a highly sensitive means of detecting ammonia gas in air. The monitoring tape for ammonia gas is based on the change in fluorescence intensity of a pH indicator (Eosine Bluish) put on the tape. Exposure to the sample including ammonia increased the pH of a solution existing in the tape. The compound produced with ammonia gas shows an excitation maximum at 460 nm and a fluorescence maximum at 550 nm. The degree of the change in fluorescence intensity was proportional to the concentration of ammonia gas at a constant sampling time and flow-rate. The tape could detect 0.1 ppm of ammonia gas at a sampling time of 40 s and a flow rate of 400 ml/min. No interference was observed from carbon monoxide (100 ppm), carbon dioxide (4.9%, v/v), nitrogen dioxide (100 ppm), sulfur dioxide (50 ppm), acetone (1%, v/v), ethanol (1%, v/v), trichloroethylene (1%, v/v), chlorine (3 ppm), or hydrogen chloride gas (5 ppm).