Method and a system for quantitatively monitoring a chemical component dissolved in a liquid medium

An apparatus for on-line optimization and control of synthesis of azo compounds, wherein a reactant of a coupling reaction taking place in a liquid chemical reaction medium is quantitatively monitored, said apparatus comprising:

• (A) a measuring cell having a measuring chamber which is configured so that an interface zone is formed within said chamber between said liquid medium and an analytical reagent solution containing an analytical reagent when said analytical reagent solution and said liquid medium are introduced into said measuring chamber by the sequence of operations defined in steps (i) and (iii) below,
• said analytical reagent being such that it reacts with said reactant in solution to form a soluble, colored reaction product, and said measuring cell comprising
• (a) a light source from which a light beam is transmitted into said measuring chamber, and
• (b0 a detector which detects light from said light beam after said beam has passed into said interface zone in said measuring chamber;
• (B) a reservoir containing said analytical reagent solution;
• and
• (C) liquid transfer means capable of introducing one or both of said liquid medium and said analytical reagent solution into said measuring chamber,
• said apparatus being configured for performing a method comprising the steps of
• (i) charging said chamber with said analytical reagent solution by means of said liquid transfer means,
• (ii) measuring a reference or baseline value of the absorbance in said analytical reagent solution present in said measuring chamber by transmitting a light beam emitted from said light source through said reagent solution, said light beam eventually impinging upon said detector so as to generate a signal whose magnitude is related to the value of the absorbance in said analytical reagent solution,
• (iii) transferring said liquid medium into said measuring chamber by means of said liquid transfer means, thereby forming said interface zone between said liquid medium and said analytical reagent solution,
• (iv) measuring a measure of the absorbance of said soluble, colored reaction product formed in said interface zone by reaction of said reactant in solution with said analytical reagent in solution, by transmitting said light beam emitted from said light source through said liquid medium, said interface zone and said reagent solution present in said measuring chamber, said light beam being emitted in a direction substantially perpendicular to said interface zone and, after passing through said interface zone, said light beam impinging upon said detector so as to generate a signal whose magnitude is related to the value of the absorbance in said interface zone, said measurement optionally being preceded by a period of time after the formation of said interface zone, and
• (v) deriving a value for a measure of the concentration of said reactant in said chemical reaction medium on the basis of the measurements made in steps (ii) and (iv), and, in those cases where said value is outside preselected limits, regulating a process parameter or controlled variable so as to bring said value within said preselected limits.