A flow procedure based on a metallic capacitance flow-through detector is described for the analysis of water vapour. The capacitance detector consists of two stainless steel tubes and is located in the loop of a sampling valve. The logarithm of the capacitance signal correlates linearly with the concentrations of water vapour in the 1705 to 2197 Pa range. A sampling frequency of about 55 h-1 can be achieved. The flow system was applied to the indirect determination of the ethanol concentration in drinks based on the analysis of water vapour content above the liquid sample, without any pre-treatment of the sample. The colour of the drinks has no effect on the measurements.
capacitance; water vapour; ethanol; drinks; flow analysis
