ONLINE RAPID DETECTION OF UREASE-PRODUCING BACTERIA WITH A NOVEL BULKACOUSTIC-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 t he growth and population of Proteus vulgaris. In this detection system , an AT-cut piezoelectric crystal is connected with a gas-sensing prob e in series. The latter is filled with an internal electrolyte solutio n which is separate from bacterial samples by a gas permeable membrane . The principle of the probe response was based on the impedance chang e of the buffer solution caused by ammonia production during the growt h 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, respons e time, pH, and temperature effects were discussed. Measurement result s were in good agreement with those from the pour plate count method. (C) 1997 Elsevier Science Inc.