Amine degradation is an important and current focus in the development of chemical absorption technology based on the use of aqueous amines for post-combustion capture (PCC) of CO2. The oxidative degradation and carbamate polymerisation of monoethanolamine (the current industry standard amine for PCC) has been studied extensively at the laboratory scale. However, methods for monitoring long-term amine degradation during pilot, demonstration and commercial scale PCC are needed to enable researchers and operators to optimise amine management (e.g. minimising degradation and optimising reclamation strategies), improve PCC plant operation and avoid operational instabilities. The current industry standard method, based on the measurement of heat-stable salts (HSS) is not suitable for continuous monitoring of amine degradation. This study discusses the organic structural changes of severely degraded 30% (w/w) aqueous monoethanolamine samples obtained from a PCC pilot plant operating at a brown coal-fired power station in Australia. It demonstrates that absorbance measurement at 313nm by UV-vis, change in infra-red absorbance and the organic carbon content of degradation products correlate strongly with HSS concentrations. These parameters are easily measured using well established technology and are suitable for monitoring the degradation of aqueous monoethanolamine during PCC.