Online water quality monitoring: issues with silicate measurement
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My factory uses a 118W online silicate analyzer from Huakeyi for pharmaceutical reagents; previously, we used the methods developed by Huakeyi for measuring sulfuric acid, ammonium molybdate, tartaric acid, and acids of types 1, 2, and 4. Later, since tartaric acid always produced some black flocculent substances, we switched to oxalic acid 1,2,4 acid, and replaced it with ammonium ferrous sulfate reagent. Will this have an impact on the color development reaction? It is also stated in the materials that oxalic acid, tartaric acid, and citric acid are all masking agents; they can react with phosphorus, iron, and arsenic present in water to eliminate interfering factors. Do these three acids have the same effect? I read in some materials that when there is a high concentration of phosphate ions in water, it is necessary to increase the concentration of citric acid. Does that mean that only citric acid can mask the interference caused by phosphorus in the water quality? Do the other two acids merely serve to carry out a secondary acidification process? 、
Currently, oxalic acid and ammonium ferrous sulfate are commonly used in instruments for measuring silicate ions. Their functions are the same as those of tartaric acid and 1,2,4-butanetriol; the only difference is that oxalic acid does not cause the formation of flocs, unlike tartaric acid (which can potentially block the reagent tubes and air pumps over time). Ammonium ferrous sulfate, on the other hand, is less prone to deterioration compared to 1,2,4, allowing for higher doses to be used over an extended period of time. Both oxalic acid and tartaric acid are secondary acids that lower the pH value, in order to reach the pH level required for the subsequent reactions; they also serve to mask certain effects. The effect of citric acid should be the same as that of the first two acids. . .