Reflectance sensor for air humidity determination

A new sensor phase based on the colour change in presence of humidity of a xanthane dye entrapped in a nafion matrix or in a cation exchanger resin is presented. The reflectance decreases with increasing relative humidity for the dye-nafion system matrix and the fluorescence increases with increasin g relative humidity for the dye-cation interchange resin system. Good rever sibility with changes of humidity are confirmed. The response time is longe r for the dye-cation exchanger system than at for the dye-nafion matrix. Th e probably sensing mechanism is proposed and the analytical potential of th e systems is outlined.