During the process of testing water samples for ammonia-nitrogen, turbidity sometimes occurs after reagents are added. Based on common inquiries from users, Lianhua Technology has compiled the following seven categories of potential causes and corresponding solutions for reference during actual operations.
1. Metal ion interference: Sample turns milky/turbid
Possible cause: Ions such as calcium, magnesium, and iron in the water sample form hydroxide precipitates in an alkaline environment.
Solution: Add potassium sodium tartrate to mask the ions; if turbidity is severe, perform flocculation and sedimentation, then test the supernatant.
2. Excessive ammonia-nitrogen concentration: Solution turns orange-red and turbid
Possible cause: The ammonia-nitrogen concentration exceeds the measurement range of the instrument or reagents, causing the colored complex to precipitate due to supersaturation.
Solution: Dilute the sample with ammonia-free water and re-test; calculate the final result based on the dilution factor.
3. Impurities or oil/grease in the sample: Milky-white turbidity
Possible cause: Silt, oil, or surfactants create turbidity or emulsions.
Solution: Filter the sample using a membrane filter; for oily samples, use absorbent cotton to remove floating oil.
4. Sulfide or organic matter interference: Grayish or hazy turbidity
Possible cause: Impurities react with reagents to form precipitates or by-products.
Solution: Add zinc acetate to remove sulfides; for complex wastewater, pre-distillation pretreatment is recommended.
5. Reagent or glassware issues: Blank sample is also turbid
Possible cause: Nessler’s reagent or potassium sodium tartrate has deteriorated or is impure, or there is cross-contamination of glassware.
Solution: Replace with fresh, qualified reagents; dedicate glassware to this specific test and rinse with ammonia-free water.
6. Operational environment factors
Possible cause: Sample pH not adjusted to neutral, color development time too long or too short, or ambient temperature too high. Recommendations: Adjust the water sample pH to neutral before testing; allow 10–15 minutes for color development; maintain the ambient temperature between 20–25°C.
7. High-salinity wastewater: Foggy turbidity
Possible cause: High salt content triggers “salting-out,” affecting the stability of the color-developing system.
Recommendations: Dilute the water sample appropriately or perform pretreatment via distillation before testing.
If the issue persists after following the steps above, please contact Lianhua Technology for remote technical support.
Note: The procedures described here are based on standard principles for ammonia-nitrogen determination. Variations may exist depending on the water sample matrix; method validation is recommended prior to actual testing.
Post time: Sep-17-2026
