A simple question: how is the alkalinity of desulfurization liquid calculated?

Alkalinity is mainly the sum of sodium carbonate and sodium bicarbonate; it is generally determined by titration with an HCl standard solution, using phenolphthalein and bromocresol green-methyl red mixed indicators. In the first step, phenolphthalein indicator is added, causing the solution to turn red. The titration is brought to an end when the red color of the solution fades; at this point, all of the Na2CO3 has been converted to NaHCO3, with a pH of around 8.2. Thereafter, the bromocresol green-methyl red mixed indicator is added drop by drop to the solution, until the color changes from green to purplish-red, which marks the end of the addition. The pH value at which this indicator changes color is around 5.4; at this point, all of the NaHCO3 has been neutralized into NaCl. The following reactions occurred throughout the titration process: Na2CO3 + HCl → NaCl + NaHCO3; NaHCO3 + HCl → NaCl + CO2 ↑ + H2O. The total alkalinity of the solution, as well as the individual concentrations of Na2CO3 and NaHCO3, can be determined based on the volume of the standard hydrochloric acid solution used in the titration. It is generally expressed in g/l or molar content, and the sodium carbonate content serves as a criterion to indicate the effectiveness of desulfurization system regeneration. Of course, depending on the alkaline salts in the desulfurization solution, adjustments are made for carbonates and bicarbonates accordingly.