The total phosphorus and total nitrogen analyzer is a precision instrument used to detect the total phosphorus and total nitrogen content in water bodies, occupying a key position in the field of water quality monitoring and analysis. Its working principle integrates technologies such as chemical digestion, color reaction, and spectral analysis, which can quickly and accurately determine the concentration of pollutants in water samples.

1. Principle of total phosphorus detection: The total phosphorus detection adopts the ammonium molybdate method. The water sample is first subjected to high-temperature and high-pressure digestion to convert organic phosphorus and polyphosphate into orthophosphate. Subsequently, in an acidic environment, orthophosphate reacts with ammonium molybdate to form phosphomolybdate, which is then reduced by ascorbic acid to form a blue complex. The complex exhibits characteristic absorbance at a wavelength of 700nm, and the total phosphorus content can be calculated by measuring the absorbance.

2. Principle of total nitrogen detection: UV spectrophotometry is used for total nitrogen detection. The water sample is digested with alkaline potassium persulfate to convert all nitrogen-containing compounds into nitrates. Next, nitrate is reduced to nitrite using a cadmium column or ultraviolet catalyst, which reacts with diazonium salts to produce azo dyes. The absorbance of this dye at specific wavelengths (such as 220nm and 275nm) is proportional to the total nitrogen content, from which the total nitrogen concentration can be calculated.

Measurement steps and usage precautions of total phosphorus and total nitrogen analyzer:

1、 Total phosphorus determination steps

1. Sample pretreatment

-Collection and storage: Collect water samples in clean glass or polyethylene bottles, immediately add sulfuric acid (or hydrochloric acid) to adjust the pH to 1-2, refrigerate at 4 ℃, and complete the measurement within 24 hours.

-Digestion treatment: Adding oxidants (such as potassium persulfate) to the water sample, converting organic and inorganic phosphorus into orthophosphate under high temperature and pressure.

-Color reaction: Under acidic conditions, ammonium molybdate and ascorbic acid reagent are added to form a blue complex.

2. Colorimetric analysis: Pour the colored sample into a colorimetric dish and place it in a total phosphorus analyzer. Measure the absorbance at a wavelength of 700nm and calculate the total phosphorus concentration based on the calibration curve.

2、 Total nitrogen determination steps

1. Sample pretreatment

-Dissolve and transform: Add alkaline persulfate to the water sample, and convert nitrogen-containing compounds into nitrate nitrogen under high temperature and pressure.

-Neutralization adjustment: After digestion, cool down and adjust the pH to neutral with hydrochloric acid.

2. Color development measurement: Under strong acidic conditions, nitrate nitrogen reacts with the color developer to form a brownish yellow complex. The absorbance is measured at a wavelength of 420nm, and the total nitrogen content is converted using a standard curve.

3、 Precautions for use

1. Safe operation

-The reagent contains corrosive substances and should be operated with gloves and goggles to avoid direct contact.

-The digestion process generates high temperature and pressure. It is forbidden to open the lid at will to prevent burns or explosions.

2. Instrument maintenance

-Regularly clean the colorimetric dish to avoid residue affecting the results; The lifespan of the light source is limited, and if it is not used for a long time, the power should be turned off.

-Before each use, check the expiration date of the reagent and the calibration status of the instrument to ensure data reliability.

3. Environmental control

-Keep the laboratory ventilated and away from strong light and vibration sources; Avoid flammable materials during digestion.

-Waste liquid shall be collected in accordance with the regulations for the treatment of hazardous chemicals and shall not be dumped at will.