A novel approach towards calibrated measurement of trace gases using metal oxide semiconductor sensors

We present a method for quantitative measurements of metal oxide semiconductor gas sensors (MOS) which is based on relaxation of surface states using temperature cycled operation (TCO). The method provides sensor response to toluene in form of a power law and a reliable quantification in the concentration range of about 10 ppb to 10 ppm. For the calibration of the sensor, a method is developed based on the equilibrium vapour headspace over a liquid solution of toluene and squalane yielding reliable concentrations in the range of 10 ppb to 600 ppm. The calibration method was shown to be stable under ambient conditions and thus to be applicable for field calibration of gas sensors.