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Analyze how the rapid detection method of ammonia nitrogen is operated

by:BOQU     2021-05-10


The rapid detection methods of ammonia nitrogen generally include Nessler's colorimetry, phenol-hypochlorite (or salicylic acid-hypochlorite) colorimetry and electrode method. Nessler's reagent colorimetric method has the characteristics of simple operation and sensitivity. The measurement of disturbances such as calcium, magnesium and iron, sulfides, aldehydes and ketones, color, and turbidity in water requires the corresponding pretreatment, phenol-time The chlorate colorimetric method has the advantages of sensitivity, stability, etc. The disturbing condition and the elimination method are the same as Nessler's reagent colorimetric method. The electrode method generally does not require pretreatment of the water sample and the advantages of a wide measurement scale. When the ammonia nitrogen content is high, distillation-acid titration can still be used.

The process of ammonia nitrogen rapid detection method:

1. Water sample pretreatment: colorless and clear water samples can be directly measured; water samples with higher chromaticity, turbidity and more disturbing substances need to be pretreated by distillation or coagulation deposition.

2. Preparation of the standard curve: pipette 0, 0.50, 1.00, 3.00, 5.00, 7.00 and 10.0mL ammonium standard use solution into a 50mL colorimetric tube, add water to the marking line, add 1.0mL potassium sodium tartrate solution, and mix Add 1.5mL Nessler's reagent evenly and mix well. After standing for 10 minutes, at a wavelength of 420nm, use a cuvette with an optical path of 10mm and use water as a reference to measure the absorbance.

From the measured absorbance, subtract the absorbance of the zero-concentration blank tube to obtain the proofreading absorbance, and make a standard curve of ammonia nitrogen content (mg) versus proofreading absorbance.

3. Determination of water sample: Take an appropriate amount of water sample (so that the ammonia nitrogen content does not exceed 0.1mg), put it in a 50mL colorimetric tube, dilute to the mark, add 1.0mL potassium sodium tartrate solution, mix, and add 1.5mL of Nessler's reagent, mix well, and place for 10 minutes.

4. Blank test: replace the water sample with ammonia-free water and make a blank test for the whole procedure.

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