Abstract: A system (1) for optically determining a concentration of a substance of interest, e.g. glucose, in a body fluid. The system (1) comprises a probe head (2) adapted to be positioned in direct contact with a body fluid to be analysed, e.g. subcutaneously, in a blood vessel or in direct contact with a sample. The probe head (2) defines an analysis volume (5) which is at least partly delimited towards the body fluid by a semi-permeable membrane (6) allowing substances of interest to enter the analysis volume (5). The system (1) further comprises first light guiding means (7) arranged for guiding primary light (9) to the analysis volume (5), and second light guiding means (8) arranged for guiding secondary light (11) away from the analysis volume (5). The primary light (9) is scattered, preferably Raman scattered, and the scattered spectrum is used for determining the concentration of the substance of interest.

Abstract: The present invention relates to a system for determining a concentration of a substance of interest in a body fluid, more specifically to systems comprising sensor devices for optically detecting compounds such as glucose. The system of the present invention is, e.g., suitable for continuous determination of a concentration of a substance of interest which is present in a body fluid, e.g. a concentration of glucose in blood or interstitial fluid.