Amperometric determination of ammonium ions with a microbial sensor

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Abstract
A sensor for NH+4 ions has been developed, which consists of immobilized micro‐organisms (Bacillus subtilis, Pseudomonas aeruginosa, Trichosporon cutaneum) in combination with an electrochemical transducer. This sensor is based on the measurement of acceleration of respiration after addition of NH+4 in the presence of glucose. The physiological background of this signal and its connection with NH+4 ion uptake and/or metabolism is discussed. The response time of the sensor is about 5.10 s for NH+4 ions. A linearity was observed between 0.005 and 0.15 mmol dm−3 NH+4 ions. The sensitivity of the sensor remained almost constant for 12 days. The sensor was used to determine NH+4 ions in a microbial fermentation broth.