What are the pre-treatment methods for total phosphorus?
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This post was last edited by sunshineda_VGMP on 2017-12-7 09:00. Total phosphorus cannot be measured directly; in the laboratory, we first preprocess the water sample by oxidizing the total phosphorus in it to a soluble phosphate form. Under specific conditions, ascorbic acid then reduces this compound, resulting in the formation of a blue complex with antimony salts. Methods for digestion include potassium persulfate oxidation and microwave digestion. The pretreatment for total phosphorus analyzers primarily employs ultrasonic crushing technology, which allows the suspended particles in the sample to be crushed using ultrasound before they are fed into the instrument, thereby reducing errors ； The subsequent measurements are basically the same as those using the spectrophotometric method, also employing the ammonium molybdate spectrophotometry.
Total phosphorus in water includes phosphate, polyphosphate, phosphite, organic phosphonic acids, and organic phosphine compounds. To determine total phosphorus, it is necessary to convert these other forms of phosphorus into phosphate, which can be easily quantified. For this purpose, the other forms of phosphorus in the sample must be appropriately converted and oxidized; this process is also known as digestion, wherein persulfate is used to oxidize the other phosphorus compounds into inorganic phosphate under neutral or alkaline conditions. Ultrasonic waves can only break down some solid or suspended substances; they cannot oxidize organic phosphorus compounds or low-valent phosphorus compounds.