Synthetic lubricant oils based on a polyol ester base stock and containing amine-based antioxidants are
characterised by fluorescence excitation–emission-matrix (EEM)spectroscopy.The main spectral
features are attributed to antioxidants and are quantified using Parallel Factor(PARAFAC) analysis.The
resulting PARAFAC component scores are compared to the relative antioxidant concentrations that were
independently obtained with linear sweep voltammetry (LSV).An excellent correlation between the
total intensity of the fluorescence signatures and the integrated LSV signal indicates that fluorescence
EEM has a potential in the real-time – online or at-line – measurements of antioxidant concentrations.A
modified fibre probe is presented that allows such measurements in strongly absorbing samples.The
fibre probe contains a bevelled window to reduce theeffects of fluorescence reabsorption and other
“inner filter” effects.