A novel bulk acoustic wave sensor for dissolved ammonia

A novel bulk acoustic wave (BAW) sensor for the detection of dissolved ammonia can be realized by using a new BAW device, in which an AT-cut piezoelectric crystal is connected in series with a probe. The probe is filled with an internal electrolyte solution that is separated from sample solutions by a gas permeable membrane. Such a gas sensor based on the BAW device can overcome the influence of water vapour and can be used in the detection of ammonia in aqueous solution. The present sensor exhibits favourable frequency response to 1 × 10−6 − 1 × 10−3 M ammonia. The limit of detection is 1 × 10−7 M. The proposed sensor has been successfully applied to the determination of ammonia in serum samples.