DETECTION OF HALOGENATED AND OTHER HYDROCARBONS IN AIR - RESPONSE FUNCTIONS OF CATALYST ELECTROCHEMICAL SENSOR SYSTEMS

A method is described for analysing gases and vapours with amperometric sensors connected to a catalytic microreactor. Stationary gas streams are switched between reference gas and sample gas by magnetic valves. This produces a step-functional change of the gas concentration at the sensor. The response function is evaluated by using exponential functions. Even for one specific gas, a sum of two or more exponential functions is required. The time-constant parameters of these functions are selective for a specific gas and independent of its concentration. The amplitude parameters are used to calculate the gas concentration. As a practical example, the analysis of a gas mixture with the four components carbon monoxide, formaldehyde, benzene and perchlorethylene is discussed, with particular emphasis on solving cross-sensitivity problems.