Abstract: A spectroscopic apparatus, a method of determining a concentration and/or spatial gradient of an analyte of a bodily fluid and a corresponding computer program product are provided. The spectroscopic apparatus provides determination of a position of a capillary vessel (104) within a biological sample in order to focus spectroscopic excitation radiation to a volume (122). that is in close proximity to the capillary vessel but does not overlap with the capillary vessel. The provided apparatus, method, and computer program product advantageously exploit the permeability of the vessel wall with respect to an analyte that is subject to analyte concentration determination. By means of biological transport processes, the concentration of an analyte of a bodily fluid located in the capillary vessel influences the concentration in the surrounding of the capillary vessel.

Abstract: The present invention provides for an apparatus and a method for determining a property of a fluid which flows through a biological tubular structure, such as blood flowing through a capillary vessel (112) under the skin (114). This enables in vivo non-invasive blood analysis. An objective (108) having a variable numerical aperture (116) is used to enable automatic detection of a blood vessel (112) and to provide a high signal to noise ratio of the return radiation for the purposes of the spectroscopic analysis and to provide a small detection volume that fits completely within the target region.

Abstract: A Raman spectrum is measured inside animal tissue, such us human skin tissue, at a selected depth from a surface the tissue. A pH value is computed using a function that assigns a pH value as a function of the measured Raman spectrum. The computation may involve computing a number representing a ratio of concentrations of a protonated and a deprotonated version of a chemical substance from the Raman spectrum and generating pH information on the basis of said number. The chemical substance is for example a form of Urocanic acid (UCA). UV exposure is measured from the weight of the spectrum of cis-UCA.