New baw sensors for dissolved gases

Novel BPES (Bulk Acoustic Wave Piezoelectric Crystal with Electrodes in Series) sensors for dissolved gases are proposed. They are based on the non-mass effect response of the sensor to the change in conductivity of the internal electrolyte solution of the sensing device, caused by the dissolved gas. Several kinds of such sensors are described for dissolved sulphur dioxide, nitrogen dioxide, carbon dioxide, and ammonia. Factors affecting the sensor performance are discussed, including buffer composition, unreacted foreign electrolyte in the internal solution, osmotic effect, and cell constant of the probe. This type of gas sensing device is advantageous over conventional potentiometric sensors for dissolved gases based on ion-selective electrodeS in their high sensitivity, fast response, not requiring either a reference electrode or a fragile glass pH electrode, and simple construction. Their applications in medicine, environmental science, food technology, and enzymology are provided.