Abstract: The invention relates to a method for adjusting the dosage of reaction components in a continuous azoic coupling reaction characterized in that the redox potential of the reaction mixture is measured online in the main flow after it exits from a continually operated reactor in a flow measurement cell with the aid of a rotating redox electrode which is arranged crosswise in relation to the direction of flow of the reaction mixture. The invention also relates to a flow measurement cell for carrying out said method, characterized by the following: a rotating redox electrode (1) which is arranged approximately in the middle of the flow pipe (2) of the flow measurement cell in a crosswise position with relation to the direction of flow of the reaction mixture and rotatably mounted in a sliding contact (3) for picking up a signal; a rod-shaped body (4) which enters into contact with the rotating redox electrode and which has a cleaning effect; a reference electrode (5) and a pH electrode (6).