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

A cryptophane-coated sensor for ammonia based upon a quartz microbalance ha s been developed and the influence of the operating temperature and humidit y have been evaluated. Whereas the time constant of the sensor reaction dec reases at higher temperature, a lower temperature yields a higher sensor si gnal. To characterize the interference of relative humidity on the determin ation of the ammonia concentration, we have constructed a scheme of isother ms based upon measurements using pulses of a carrier gas (purge-pulse (PP) method). This scheme of isotherms enables us to explain and estimate the ef ficiency of the PP and of the alternate temperature-pulse (TP) method. (C) 1999 Elsevier Science S.A. All rights reserved.