Device and a method for light-based analysis of a substance in a liquid sample

A device for light-based analysis of a substance in a liquid sample, said device comprising:

• an analysis cell for holding the liquid sample during analysis;
• an inlet and outlet for transporting the liquid sample to and from the analysis cell;
• a light source for generating light for illuminating the liquid sample in the analysis cell;
• a light detector for detecting light, wherein the light detector and the light source are arranged on opposite sides of the analysis cell such that the light detector is configured to detect light having passed through the liquid sample;
• and
• a plunger configured to fit in the analysis cell and configured for movement along walls of the analysis cell for allowing entry of the liquid sample into the analysis cell and pushing the liquid sample out of the analysis cell,
• wherein the plunger comprises a first portion having a first thickness corresponding to a cross-section of the analysis cell and a second portion having a second thickness which is smaller than the first thickness for allowing a first analysis measurement to be performed while the second portion of the plunger is arranged between the light source and the light detector such that light being detected by the light detector is passed through the second portion and through the liquid sample between the second portion of the plunger and a wall of the analysis cell,
• wherein the plunger is movable to a completely retracted position in the analysis cell for allowing a second analysis measurement to be performed such that light being detected by the light detector is passed through the liquid sample filling a space between opposite walls of the analysis cell, and
• wherein the first portion of the plunger comprises a reference block, which is configured to be arranged in a light path in the analysis cell between the light source and the light detector in a calibration measurement, wherein the reference block is transparent to the light generated by the light source.