Fluorescence excitation emission matrix spectroscopy of strongly absorbing samples using fibre-optic probes

Fibre-optic probes play an increasing role in the investigation of a variety of condensed media, for example in the food industry, in medicine and in the oil industry. Using single fibres or fibre bundles fluorescence can be excited and collected even if the samples are strongly absorbing such as process liquids and lubricants. In combination with fluorescence excitation-emission matrix (EEM) spectroscopy two dimensional data arrays are generated that contain qualitative and quantitative information about the composition of the sample. In this report we explicitly consider the effects of primary and secondary absorption in fluorescence EEM spectroscopy, and identify the optimal detection configuration of the fibre-optic fluorescence probe facilitating the largest possible dynamic concentration range. Theoretical results were validated with in situ measurements of strongly absorbing machinery fluids.