Detection of Trace concentrations of gases with coated piezoelectric quartz crystals

Coated piezoelectric crystal sensors for determination of trace constituents in gases are very sensitive. Detection limits down to the sub-ppb range have been reported, using injection techniques. From previous and presented data, this high sensitivity is found to be in disagreement with Sauerbrey's eqn., which allows a maximum sensitivity of about 1 ppm. By considering the adsorption of the gases on the coated surface and the calibration procedures used, the validity of Sauerbrey's eqn. is discussed.