Fuel cells are probably the most efficient way to achieve the difficult purpose of the so-called zero emission vehicles. In comparison to today's automotive emission monitoring applications, fuel cell emission monitoring meets the greatest challenge. In particular, the formation of hydrogen from liquid fuels produces the most dramatic changes in bulk gas compositions. During startup and in stationary conditions, gas concentrations of H2O, O2, N2, CO2, CO and methanol in the fuel cell may vary from 0 to 60 Vol%, C1 to C4 hydrocarbons from 0 to 5 Vol% [1]. Whichever physical principles and technologies are applied in the gas analyzing equipment, they are subject to more or less interference caused by the bulk gas.
A new dilution device consisting of pressure reduction stages and four compression stages with regulated dilution inputs is presented in this paper. Measurements of all relevant gaseous bulk compounds are compared in different background matrices by the use of a chemical ionization mass spectrometer (CI-MS).
Impurity components in low concentration levels, which are less affected by the matrix but more by the dilution are detected to 2-ppm levels. Dynamic and time responses as well as possible memory effects are demonstrated on a methanol-hydrogen reformer.