Influence of relative humidity in sensing halogenated hydrocarbons with Reflectometric Interference Spectroscopy (RIfS)

For stand-alone sensor systems apart from defined laboratory circumstances sensors are required, which show a high stability against perturbing enviro nmental influences like the relative humidity (r.h.). We present a portable sensor system, which is capable to quantify tetrachloroethene (TCE) in hum id air. The system works highly reproducible and shows only negligible cros s-sensitivity towards relative humidity. This allows a single calibration v alid from 0 to 80% r.h.. Therefore, referencing with an extra sensor for hu midity is not necessary. Binary mixtures of TCE and freone R113 were quanti fied for O and 40% r.h. with a root mean square error of prediction of appr oximately 3% with respect to the maximum concentration of TCE and R113, The sensitive elements used in the experiments consisted of thin polymer films on glass substrates. The measurements were performed with the optical meas urement technique RIfS (Reflectometric Interference Spectroscopy).