The application of liquid chromatography coupled to mass spectrometry (LC-MS) for the analysis of epoxy resins is shown in two examples. Electro spray (ESI) and atmospheric pressure chemical ionization (APCI) are compared with respect to the ionization of diglycidylether of bisphenol A-based (DGEBA) epoxy resins. By-products in a typical modified solid DGEBA-based epoxy resin and in a new weatherable crosslinker for powder coating applications are characterized and discussed.