Application of 220nm and 275nm filters in total nitrogen detection

At present, most water quality tests require the detection of total nitrogen content. There are various types of nitrogen in water, including organic nitrogen-containing compounds, nitrite nitrogen, inorganic ammonium salts, nitrate nitrogen, and dissolved ammonia, which can be converted into each other through biochemical reactions. Total nitrogen refers to the total amount of soluble nitrogen and nitrogen content in suspended particles. When the nitrogen and phosphorus content in surface water is too high, the water becomes eutrophic, leading to the proliferation of microorganisms, vigorous growth of phytoplankton, and deterioration of water quality. Therefore, detecting total nitrogen is a commonly used method for water quality testing.

Technical principle and advantages of total nitrogen detection instrument:

The water sample is first mixed with an alkaline potassium persulfate solution, and then subjected to UV digestion and high-temperature digestion. The total nitrogen in the water is converted to nitrate; After mixing with HCl solution, eliminate NaOH interference and pass through two flow detectors to determine the response signal of the water sample; Calculate the correction signal according to the formula, and the total nitrogen content is proportional to the correction signal; Including: peristaltic pump, mixing reaction loop, UV digestion device, heating cell, bubble removal device, dialyzer, first flow detection cell, second flow detection cell. The advantages reduce the errors caused by manual use of colorimetric tubes and pipettes, greatly improving the accuracy and repeatability of detection results; Improved the safety of the experimental process and saved the cost of instrument operation; Due to the use of fewer reagents, it also reduces the probability of instrument failure and increases the stability of the instrument.

Testing steps:

1. The water sample is first mixed with an alkaline potassium persulfate solution, and then subjected to UV digestion and high-temperature digestion at 107 ℃ to 110 ℃. The total nitrogen in the water is converted to nitrate;

2. After mixing with HCl solution to eliminate NaOH interference, the water sample was subjected to two flow detectors to determine the response signals A220 and A275 at 220nm and 275nm, respectively;

3. Calculate the correction signal A according to formula A=A220-2A275, and the total nitrogen content is proportional to the correction signal A.

From this, it can be seen that the reason for using narrowband filters at 220nm and 275nm is because nitrate ions have a characteristic large absorption at 220nm ultraviolet light, while there is basically no absorption at 275nm; Dissolved organic matter absorbs at both 220nm and 275nm, therefore absorbance A220 and A275 can be measured at 220nm and 275nm, respectively.

Ruicheng Optoelectronics has developed and optimized 220nm and 275nm ultraviolet narrowband filters specifically for water quality analysis. Currently, they have passed multiple customer tests with excellent feedback. Their spectral curves can be found on the company's product page. If you need them, please contact our business personnel.