Abstract: A chemical analysis apparatus is disclosed as having a liquid flow train assembly for creating a flowing liquid sample stream guided from a sample inlet through the apparatus in a capillary tubing arrangement at low liquid flow rates, the sample containing an analyte to be measured; a reagents dosing and injection device located downstream the sample inlet for introducing a series of chemical reagents into the sample stream; a reactor where the reagents react with the analyte for producing a colored chemical indicator in the fully reacted sample; and a detection for measuring the chemical indicator, located downstream of the reactor means and being configured to receive the fully reacted sample with the colored indicator from the reactor means. The flow train assembly can intermittently let the fully reacted sample pass through the detector when the measurement of the indicator is not made, and to bypass the detector when the measurement of the chemical indicator in the sample is made.