On-line rapid detection of urease-producing bacteria with a novel bulk acoustic wave ammonia sensor

As an attractive alternative to the sensors currently in use, a novel bulk acoustic wave (BAW) ammonia gas sensor was developed to monitor the growth and population of Proteus vulgaris. In this detection system, an AT-cut piezoelectric crystal is connected with a gas-sensing probe in series. The latter is filled with an internal electrolyte solution which is separate from bacterial samples by a gas permeable membrane. The principle of the probe response was based on the impedance change of the buffer solution caused by ammonia production during the growth of bacteria. The detection ranges are from 1.2 x 10(2) to 1 x 10(7) cells ml(-1). Linear and nonlinear regression methods are employed for the bacterial numbers in samples. In addition, dynamic range, response time, pH, and temperature effects were discussed. Measurement results were in good agreement with those from the pour plate count method. (C) 1997 Elsevier Science Inc.