Fuel cells are electrochemical systems that convert hydrogen into electricity without combustion. Proton exchange membrane (PEM) fuel cell power systems consist of a polymer membrane, finely dispersed catalyst and a gas humidifying system. Thermogravimetry (TGA) and differential scanning calorimetry (DSC) can be used to characterize the physical properties of a polymer membrane. Ion chromatography can monitor the presence of contaminating ions in the aqueous condensate. TGA can measure decomposition of the polymer material and the residual metal catalyst that remains, which can be correlated to the distribution of metal catalysts on a polymer surface. DSC can be used to measure the concentration of Teflon in a polymer blend by measuring the melting enthalpy. Published by Elsevier Science B.V.