Q1: When testing ammonia nitrogen, is it measured in terms of nitrogen element or ammonium ions?
Answer: Ammonia nitrogen refers to the sum of nitrogen in the form of free ammonia (NH₃) and ammonium ions (NH₄⁺) in water, so the ammonia nitrogen we usually test is measured in terms of nitrogen.
Q2: When testing ammonia nitrogen, will the pH value of the water sample have an impact?
Answer: The determination of ammonia nitrogen requires that the water sample is preferably neutral, and the color development of ammonia nitrogen requires alkalinity. Because our reagent is alkaline, neutrality and alkalinity have no effect. If the water sample is acidic, it will neutralize part of the alkali solution, and the test result will be lower.
Q3: What is the reason for the orange turbidity generated after the reagent is added to the water sample?
Answer: After the reagent is added to the water sample, the entire reaction tube produces orange-red turbidity or orange-red sinks to the bottom. Generally, the ammonia nitrogen concentration is too high, and the water sample needs to be diluted a large multiple before testing.
Q4: What is the reason for the white precipitate generated after the reagent is added to the water sample?
Answer: Water samples contain heavy metal ions, which can be removed by flocculation and precipitation. Add 1 mL of zinc sulfate solution and 0.1~0.2 mL of sodium hydroxide solution to every 100 mL of sample, adjust the pH to about 10.5, mix well, let it settle, and take the supernatant for analysis. If necessary, filter with medium-speed filter paper rinsed with water, discard 20 mL of the initial filtrate, or centrifuge the sample after flocculation.
Q5: What is the reason for the brown colloidal turbidity in the reaction tube after adding N2 reagent?
Answer: There is residual chlorine interference in the water sample, which can be removed by adding an appropriate amount of sodium thiosulfate (3.5g/L). Every 0.5 mL can remove 0.25 mg of residual chlorine. Starch-potassium iodide test paper can be used to determine whether the residual chlorine has been removed (if there is residual chlorine, iodine will be replaced, and iodine will turn blue when it meets starch). After eliminating the influence of residual chlorine, test again.
Q6: After adding N2 reagent, the solution behavior is bright yellow or bright yellow turbid, and the greater the dilution multiple, the higher the measured value. How to solve it?
Answer: In this case, there may be organic interference in the water sample. For low-boiling point organic matter, evaporation can be used to remove it, and for high-boiling point organic matter, water sample pre-distillation method is used. The water sample is tested after pretreatment.
Q7: Will the high residual chlorine content in the water sample affect the detection of ammonia nitrogen?
Answer: The presence of a large amount of residual chlorine will affect the color development of Nessler’s reagent. The residual chlorine will react with the iodine ions in the reagent to generate iodine, causing the reagent to be unable to be used normally.
Q8: The water sample is orange-yellow in color. How to test it?
Answer: Use a water sample diluted by the same multiple as a blank to deduct the background interference caused by the chromaticity.
Q9: Flocculent precipitation is produced after the reagent is prepared. After adding the reagent, the blank shows orange-yellow. What is the reason?
Answer: The experimental utensils or pure water used are contaminated. Clean and replace the experimental utensils and pure water before conducting the experiment.
Q10: How to deal with abnormal color development when measuring ammonia nitrogen by salicylic acid method?
Answer: There are other ion interferences in the water sample, and the water sample can be pretreated by flocculation and precipitation. Flocculation and precipitation: Add 1 ml zinc sulfate solution and 0.1~0.2 ml sodium hydroxide solution to 100 ml sample, adjust the pH to about 10.5, mix well, let it settle, and pour the supernatant for analysis. If necessary, filter with medium-speed filter paper rinsed with water, discard 20 ml of the initial filtrate, or centrifuge the sample after flocculation.
Q11: How to measure ammonia nitrogen in sodium acetate carbon source water sample?
Answer: The carbon source is organic matter interference. Dilute the sodium acetate content to less than 5%, and use salicylic acid method low-range reagent for detection.
Q12: The standard solution is measured normally with Nessler’s reagent, but no color is developed when detected with salicylic acid reagent. What is the reason?
Answer: The salicylic acid reagent may be contaminated or expired. The LH-NH3-SAH3 reagent is shipped as a solid-liquid separation reagent, ready to use, and has a shelf life of 1 month after preparation. It is recommended to store it in a refrigerator to appropriately extend the shelf life of the reagent. At the same time, it is also necessary to strictly prevent cross contamination during the experiment, and the reagents must be stored strictly away from light.
Q13: What is the relationship between Kjeldahl nitrogen, ammonia nitrogen, and nitrate nitrogen?
Answer: Kjeldahl nitrogen is the nitrogen content in water measured by the Kjeldahl method (Kjeldahl method). It includes ammonia nitrogen and organic nitrogen compounds (such as proteins, amino acids, nucleic acids, etc.) that can be converted into ammonium salts under certain conditions and accurately measured. Therefore, ammonia nitrogen is part of Kjeldahl nitrogen. In the nitrogen cycle, organic nitrogen compounds (including the organic nitrogen part of Kjeldahl nitrogen) can be decomposed by microorganisms and converted into ammonia nitrogen, and then further oxidized into nitrite nitrogen and nitrate nitrogen. Therefore, the organic nitrogen part of Kjeldahl nitrogen can be converted into nitrate nitrogen in the nitrogen cycle.
The above are some common problems and solutions for using Lianhua water quality analyzer to conduct ammonia nitrogen experiments. If you encounter other difficult problems in ammonia nitrogen experiments, please leave a message and ask questions. Our after-sales service team will answer you in detail!
Post time: Feb-17-2025
