Issues regarding the determination of total phosphorus in circulating water
Thread Content
Recently, the determination of total phosphorus has been unreliable: no color development occurs after 10 minutes, while a darker color appears after 60 minutes. But there were no issues with the determination of orthophosphorus. I suspect potassium persulfate isn’t effective. Can potassium persulfate be replaced with any other reagent? Additionally, potassium persulfate is added when measuring calcium and magnesium to eliminate the effect of organophosphorus compounds. What impact does this have on the determination of calcium and magnesium? Thank you
Could you tell me the method you used? (To measure total phosphorus in circulating water)
Organic phosphonates or phosphonocarboxylates are generally added to circulating water as scale inhibitors; when determining total phosphorus, the sample must be treated with persulfate under alkaline or neutral conditions to oxidize the organic phosphons to phosphate ions before measurement. Anhydrous persulfuric acid or sodium persulfate can be used as a substitute for potassium persulfate, since the strong oxidizing power of persulfate ions is greatest under neutral and alkaline conditions, and the oxidation products are single, resulting in no ions that could interfere with the measurement. When determining calcium and magnesium, the samples are treated with persulfate; this is also done to destroy organic phosphonates in the water, so that the calcium and magnesium ions can be converted from a strongly complexed state to an ionic state, thereby ensuring reliable results in the measurements.
Dear academician, hello. I would like to ask, isn’t sulfuric acid needed when determining total phosphorus in circulating water according to national standards? Isn’t it under acidic conditions? Is measuring calcium and magnesium also done to prevent complexation between organophosphorus and calcium and magnesium?
Persulfates are used for sample digestion, not for sample color development.