The lack of water resources in China has been verified. In the northern rivers with small flows, it is affected by the production and domestic sewage. The pollution is very serious, and the ammonia nitrogen exceeding the standard is very serious. Therefore, it is particularly important to monitor ammonia in the surface water and the drainage of enterprises and institutions. Traditional ammonia nitrogen determination methods are usually Nessler's reagent photometric colorimetric method (Nessler's method), salicylic acid-hypochlorite colorimetric method, distillation-acid titration method, gas phase molecular absorption method. The automatic Kjeldahl nitrogen analyzer can effectively detect ammonia in water.
The above methods are accurate for both the national standard method and the environmental monitoring method. However, when the water sample is subjected to distillation pretreatment, it takes time. We use the automatic Kjeldahl tester to measure the ammonia in the water sample. After analyzing the quality control sample and comparing it with the Nessler's colorimetric method, we can use the automatic Kjeldahl tester (Kiehl method) to obtain satisfaction. the result of.
The main working principle of the automatic Kjeldahl determination instrument is the determination of the content by distillation method. When the determination of ammonia nitrogen, the water sample is directly digested without basic digestion and is adjusted to slightly alkaline distilled ammonia, absorbed by boric acid solution, and then automatically titrated by potentiometric titrator. . After the boric acid solution absorbs ammonia, the pH of the solution rises, and the pH of the solution is titrated with the sulfuric acid solution to the initial pH value. The pH meter controls the titration end point. When the end point is reached, the titration rate decreases, and the ammonia nitrogen content in the water sample is calculated using the amount of sulfuric acid consumed.
The Kjeldahl method was used to measure the environmental standard samples. The measured values ​​all fell within the guaranteed value range and met the environmental monitoring requirements. The results are shown in Table 2. For different concentrations of samples measured by Kjeldahl method, the recovery rate of spiked standard was 90.7%~108.0%. The results are shown in Table 3. For samples with different concentrations determined by Kjeldahl method, the RSD of each concentration was 0.22% to 3.1%.
In summary, the Kjeldahl automatic Kjeldahl instrument has the advantages of simple operation, convenience, safety and reliability, short experimental analysis cycle, and small amount of reagents. The monitoring results are of high accuracy and precision.
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