Temperature dependence of an ammonia sensor in humid air based on a cryptophane-coated quartz microbalance

Abstract A cryptophane-coated sensor for ammonia based upon a quartz microbalance has been developed and the influence of the operating temperature and humidity have been evaluated. Whereas the time constant of the sensor reaction decreases at higher temperature, a lower temperature yields a higher sensor signal. To characterize the interference of relative humidity on the determination of the ammonia concentration, we have constructed a scheme of isotherms based upon measurements using pulses of a carrier gas (purge-pulse (PP) method). This scheme of isotherms enables us to explain and estimate the efficiency of the PP and of the alternate temperature-pulse (TP) method.