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Total phosphorus detection methods and precautions

by:BOQU     2022-02-26

Total phosphorus detection method Determination principle:

The sample was digested with potassium persulfate under neutral conditions, and all the phosphorus contained was oxidized to orthophosphate. In the acidic medium, orthophosphate will react with ammonium molybdate, and in the presence of antimony salt, phosphorous molybdenum heteropoly will be formed, and then a blue complex will be formed, which will be placed at room temperature for 15 minutes, using a cuvette with an optical path of 10mm or 30mm. The absorbance was measured at a wavelength of 700 nm with pure water as a reference.

Detection method steps:

Step 1: Take 5mL of water sample into the micro-return tube, add 1.0ml of potassium peroxodisulfate, pay attention to dry the water on the outer wall of the micro-return tube, and then put it in a digester to digest 30 at a temperature of 120 degrees. After cooling, select the dilution ratio according to the situation, and transfer it into a 25ml colorimetric tube.

Step 2: Add 0.5ml of color aid and 1ml of color developer dropwise, cover tightly and shake well, so that the agent and the sample are fully reflected, and let stand for 15 minutes.

Step 3: Move the water sample to the colorimetric tube, and use the light wave with the wavelength of 700nm for detection. The reading multiplied by the dilution factor is the true value of total phosphorus.

Notes on total phosphorus detection method:

1. Colorimetric process: Select the curve (No. 0), put the blank cuvette into the colorimetric cell, close the lid and press the (set/blank) key after the data is stable, it will display 'total phosphorus 0mg/L, T u003d100%”; then put the water sample cuvette into the colorimetric cell, close the lid and record the value after the reading is stable, the displayed value is the total phosphorus concentration of the water sample; if the water sample is measured after dilution, the displayed value is multiplied by the dilution The multiple is the total phosphorus concentration of the original water sample.

2. The curve (No. 0) is the factory-set curve of the instrument, which can be directly used to measure water samples. If the measurement conditions are changed, the result will have a large deviation, please use this reagent and method, and then use the standard solution to calibrate the curve , select the calibrated curve for water sample measurement.

3. The quality of the reagent has a great influence on the determination, it is recommended to use the original reagent.

4. The waste liquid generated after the test must be stored centrally and sent to a qualified unit for processing. To avoid polluting the environment, please do not dump it at will.

5. If the sample has precipitation, please carefully pour the supernatant into the cuvette; the water sample measurement process should be continuous and compact, and the sample cannot be placed for a period of time or repeated in different time periods.

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