carrier. The set point of the water bath was 30.1 C which corresponds
to a water mole fraction of 4.2% in the carrier gas at atmospheric
pressure. Nevertheless, the water fraction measured by a
cold mirror dew point hygrometer (CMH-1, Alpha Moisture
Systems, UK) used to calibrate the water signal for the QMS, indicated
that this value oscillated between 5.0 and 5.5%, depending on
the lab temperature. These differences are taken into account later.