horiba TPNA-500, Инструкция по эксплуатации

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Material
225

Total phosphorus: Ultraviolet oxidative dissolution - Molybdenum blue
spectrophotometric method
The total phosphorus compounds to be drained contain organic phosphorus compounds,
condensed phosphates, and other inorganic phosphates, when largely divided.
The concentration of total phosphorus compounds in the drained sample can be obtained by
dissolving the organics within the sample by potassium persulfate and determining the
quantity of phosphoric ions in the solution.

Principle
Add potassium persulfate and sulfuric acid to a sample and apply ultraviolet irradiation. The
phosphorous compounds in the sample are dissolved to orthophosphoric acid (PO
4
3-
).
Phosphoric ion generates molybdenum blue through reaction with phosphomolybdic acid and
ascorbic acid under acidic conditions. Measure the absorbance of the molybdenum blue at the
absorption wavelength of 880 nm and obtain the total phosphorus concentration.

Total phosphorus measurement flow

Features and application
There are two methods to dissolve samples: autoclave method and ultraviolet oxidation
method. With the ultraviolet oxidation method (potassium persulfate is added), sample
dissolution can be performed at a lower temperature (approximately 95

C) compared with the
chemical analysis method, such as autoclave method.