DEVELOPMENT OF LONG-TERM STABLE AMMONIUM ION SENSOR IN CONJUNCTION WITH A MICROBIAL MEMBRANE

An ammonium ion sensor, stable over a long time frame, was developed f or the continuous monitoring of ammonium ion in sewage. The sensor con sists of a plasticized poly (vinyl chloride) membrane-based ammonium i on sensor, in which the sensing membrane was covered with a microbial membrane (microorganism: Trichosporon cutaneum). The developed ammoniu m ion sensor completely eliminated interference from cationic surfacta nts as the result of attaching the microbial membrane to the sensing m embrane. The sensor could be utilized for continuous monitoring in sew age for over 120 days, while the performance of the ammonium ion senso r without the microbial membrane deteriorated within 5 days. The impro vement of long-term stability of the developed sensor is due to the fa ct that Trichosporon cutaneum in the microbial membrane effectively as similated organic compounds, such as ionic surfactants, from the sewag e and the sensing membrane of the sensor was prevented from coming int o direct contact with organic compounds. A regression line of Y = 1.01 X + 0.962 x 10(-4) with a correlation factor of 0.999 was obtained bet ween the analytical results of the present sensor method (Y) and those of a conventional method (X) for the determination of ammonium ion in a sewage sample. (C) 1998 Elsevier Science S.A. All rights reserved.