Photometric method and apparatus for measuring a liquid's turbidity, fluorescence, phosphorescence and/or absorption coefficient

A flow cell for use with an apparatus for deriving at least one property of a sample liquid from measuring emitted light emitted from said sample liquid upon irradiation of said sample liquid with a probe light beam, said flow cell comprising a container for containing said sample liquid forming a sample surface, said container comprising:

• a main section, at which said probe light beam is to be directed and through which said emitted light is to be emitted out of said sample liquid for being measured;
• an inlet section for receiving sample liquid to be measured, having at least one opening to said main section located beneath said sample surface;
• an outlet section for removing sample liquid from said container, having at least one opening to said main section located beneath said sample surface;
• an optical barrier arranged in said main section configured and arranged for blocking a propagation of light originating from reflection or scattering of said probe light beam at said sample surface;
• and
• a separating member for substantially separating said sample liquid in said inlet section from said sample liquid in said main section.

Method for deriving at least one property of a sample liquid comprising the steps of

• providing in a container comprising a main section and an inlet section for receiving the sample liquid, a sample liquid having an at least substantially horizontally aligned sample surface;
• generating a probe light beam;
• directing, from above, said probe light beam along a path at a portion of said sample surface in said main section in a direction forming an angle β≠0° with respect to a surface normal of said sample liquid;
• detecting an intensity of emitted light emitted upon irradiation of said sample liquid with said probe light beam
• from said sample liquid and
• through said sample surface in said main section and out of said sample liquid generally along a first detection axis, said first detection axis forming an angle γ1≠0° with a surface normal of said sample surface,
• by means of a detector detecting an intensity of light propagating above said sample surface along said first detection axis;
• blocking a propagation of light originating from reflection or scattering of said probe light beam at said sample surface towards and into said detector;
• supplying sample liquid to be measured to said inlet section;
• receiving in said main section sample liquid from said inlet section through at least one opening located beneath said sample surface;
• and
• substantially separating a portion of the sample surface belonging to said inlet section from said portion of said sample surface belonging to said main section.