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 for the continuous monitoring of ammonium ion in sewage. The sensor consists of a plasticized poly (vinyl chloride) membrane-based ammonium ion sensor, in which the sensing membrane was covered with a microbial membrane (microorganism Trichosporon cutaneum). The developed ammonium ion sensor completely eliminated interference from cationic surfactants as the result of attaching the microbial membrane to the sensing membrane. The sensor could be utilized for continuous monitoring in sewage for over 120 days, while the performance of the ammonium ion sensor without the microbial membrane deteriorated within 5 days. The improvement of long-term stability of the developed sensor is due to the fact that Trichosporon cutaneum in the microbial membrane effectively assimilated organic compounds, such as ionic surfactants, from the sewage and the sensing membrane of the sensor was prevented from coming into direct contact with organic compounds. A regression line of Y = 1.01X + 0.962 x 10⁴ with a correlation factor of 0.999 was obtained between 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.