Ammonia nitrogen (NH3-N) is present in water as free nitrogen (NH3) or (NH4+). The composition ratio of the two depends on the pH and water temperature of the water. When the pH is higher, the proportion of free ammonia is higher. On the contrary, the proportion of ammonium salt is high and the water temperature is the opposite.
The sources of ammonia in water are mainly the decomposition products of nitrogen-containing organic matter in domestic sewage by microorganisms, some industrial waste water such as coking wastewater and synthetic ammonia fertilizer plant wastewater, and farmland drainage. In addition, in the absence of oxygen, the nitrite present in the water can also be affected by microorganisms and reduced to ammonia. In an aerobic environment, ammonia can also be converted to nitrite and even converted to nitrate.
The determination of various forms of nitrogen compounds in water helps to assess water contamination and “self-purificationâ€.
Fish are more sensitive to ammonia in water. When the ammonia nitrogen content is high, it can cause fish to die.
1. Method selection Ammonia nitrogen is usually determined by Nessler's colorimetric method, gas phase molecular absorption method, phenol-hypochlorite (or salicylic acid-hypochlorite) colorimetric method, and electrode method. Nessler's reagent colorimetric method is characterized by simple and sensitive operation. The metal ions such as calcium, magnesium and iron in water, sulfides, aldehydes and ketones, color, and turbidity all interfere with the determination and need to be pretreated accordingly. The phenolic chlorate colorimetric method has the advantages of being sensitive and stable, and the interference and elimination methods are the same as those of the Nessler reagent colorimetry. The electrode method has the advantages that there is usually no need for pretreatment of the water sample and a wide measurement range, but there are some problems with the life and reproducibility of the electrode. Gas-phase molecular absorption method is relatively simple, and special instruments or atomic absorption instruments can achieve good results. When the ammonia nitrogen content is high, distillation-acid titration may be used.
2. Preservation of water samples Water samples shall be collected in polyethylene or glass bottles and analyzed as soon as possible. If necessary, sulfuric acid may be added to acidify the samples to PH<2 and stored at 2～50C. Acidified samples should be protected against ammonia contamination in the air.
(I) Pretreatment of water samples
Water samples are colored or turbid and contain other substances that affect the determination of ammonia nitrogen. For this reason, appropriate pretreatments are required for analysis. For cleaner water, flocculation and sedimentation can be used; for polluted water or industrial wastewater, distillation is used to eliminate interference.
Flocculation and precipitation method Add appropriate amount of zinc sulfate to the water sample, and add sodium hydroxide to make it basic, generate zinc hydroxide precipitate, and then filter to remove color and turbidity.
1. Instrument: 100 stuffed cylinder or colorimetric tube.
2, reagent 110% zinc sulfate solution: Weigh 10 zinc sulfate dissolved in water, diluted to 100.
225% sodium hydroxide solution: Weigh 25 sodium hydroxide dissolved in water, diluted to 100, and stored in polyethylene bottles.
3 Sulfuric acid, Ï=1.84.
3. Steps Take 100ml of water sample in stoppered cylinder or colorimetric tube, add 1ml of 10% zinc sulfate solution and 0.1-0.2ml of 25% sodium hydroxide solution, adjust the pH to about 10.5, and mix. The precipitate was left to stand, filtered through a medium-speed filter paper thoroughly washed with ammonia-free water, and 20 ml of the primary filtrate was discarded.
Distilled water regulates the pH of the water sample so that it is in the range of 6.0 to 7.4. An appropriate amount of magnesium oxide is added to make it slightly acidic, and ammonia released by distillation is absorbed in the sulfuric acid or boric acid solution. When using Nessler's colorimetric method or acid titration method, boric acid solution is used as the absorbing solution; when using salicylic acid-hypochlorite colorimetric method, sulfuric acid solution is used as the absorbing solution.
1. Instrument: Nitrogen-adjusting distillation apparatus with nitrogen ball: 500-ml Kjeldahl flask, nitrogen ball, straight condensing tube and conduit, as shown in the figure.
2. Reagents: Ammonia-free water is used for dilution of the water sample and reagent configuration.
1) No ammonia preparation:
1 Distillation method: add 0.1 ml of sulfuric acid per liter of distilled water, redistill it in an all-glass distiller, discard 50 ml of initial sulfur liquid, and take in the remaining distillate in a glass jar with a mouthwash, and store it in a tampoon.
2 Ion exchange method: Distilled water is passed through a strongly acidic cation exchange resin column.
2) 1mol/L hydrochloric acid solution.
3) 1 mol/L sodium hydroxide solution.
4) Lightweight Magnesium Oxide: Magnesium oxide is heated at 500°C to remove carbonate.
5) 0.05% Bromophenol blue indicator solution (pH=6.0~7.6)
6) Anti-foaming agents, such as paraffin fragments.
7) Absorbent:
1 boric acid solution: Weigh 20g of boric acid dissolved in water and dilute to 1L.
2. Interfere with and eliminate organic compounds such as aliphatic amines, aromatic amines, aldehydes, acetone, hydrazines and organic chloramines, as well as inorganic ions such as iron, manganese, magnesium, and sulfur, which may cause interference due to the generation of a different color or turbidity. Color and turbidity also affect colorimetry. For this purpose, it must be subjected to flocculation precipitation filtration or distillation pretreatment, volatile interfering substances, and can also be heated under acidic conditions to remove. Interference with metal ions can be eliminated by adding an appropriate amount of masking agent.
3. Scope of application of the method The minimum detection concentration of this method is 0.025 mg/L (photometric method), and the upper limit of determination is 2 mg/L. Using visual colorimetry, the minimum detectable concentration was 0.02 mg/L. After appropriate treatment of water samples, the method can be applied to the determination of ammonia nitrogen in surface water, groundwater, industrial wastewater and domestic sewage.
4, instrument 1 spectrophotometer 2 pH meter 5, reagents: reagent water should be configured without ammonia 1) Nessler's reagent: You can choose one of the following methods to prepare.
1 Weigh 60g of potassium iodide and dissolve it in 100ml of water. Add a small amount of mercury dichloride (HgCl2) crystal powder (about 10g) while stirring until the vermilion precipitate does not dissolve easily. Add saturated mercury dichloride dropwise. Solution, and fully stirred, when there is little trace of red precipitation is not easy to dissolve, stop dropping mercury chloride solution.
Another 60g of potassium hydroxide was dissolved in water and diluted to 250ml. After sufficiently cooling to room temperature, the above solution was slowly poured into potassium hydroxide solution, diluted with water to 400ml, and mixed. Let stand overnight. The supernatant was transferred into a polyethylene bottle and stored in a stopper.
2 Weigh 16g of sodium hydroxide, dissolved in 50ml of water, and fully cooled to room temperature. Another said to take 7g of potassium iodide and 10g of mercury iodide (HgI2) dissolved in water, and then this solution was slowly injected into the sodium hydroxide solution under stirring, diluted with water to 100ml, stored in a polyethylene bottle, tampons preserved.
2) Potassium sodium tartrate solution: Dissolve 50g of sodium potassium tartrate (KNaC4H4O6? 4H2O) in 100ml of water, boil it to remove ammonia, let cool, and dilute to 100ml.
3) Ammonium standard stock solution: Weigh 3.819 g of superior pure ammonium chloride dried at 100°C and dissolve in water. Pipette into a 1000-volume flask and dilute to the mark. This solution is 1.00 mg ammonia nitrogen per ml.
4) Ammonium standard use solution: Pipette 5.00ml ammonium standard stock 500ml volumetric flask and dilute to the mark with water. This solution contains 0.010 mg of ammonia nitrogen per ml.
6. Steps (1) Drawing of the standard curve 1 Use 0, 0.5, 1.00, 3.00, 5.00, 7.00 and 10.0 ammonium standards.
To assure the quality, we will do 100% inspection for raw material, production procedure, packing before shipment,
so we do have the confidence to supply customers with high-quality and high-efficiency products.
"Customer satisfaction" is our marketing purposes,so we have extensive experience in professional sales force,and strongly good pre-sale, after-sale service to clients. We can completely meet with customers' requirements and cooperate with each other perfectly to win the market.Sincerely welcome customers and friends throughout the world to our company,We strive hard to provide customer with high quality products and best service.
The sources of ammonia in water are mainly the decomposition products of nitrogen-containing organic matter in domestic sewage by microorganisms, some industrial waste water such as coking wastewater and synthetic ammonia fertilizer plant wastewater, and farmland drainage. In addition, in the absence of oxygen, the nitrite present in the water can also be affected by microorganisms and reduced to ammonia. In an aerobic environment, ammonia can also be converted to nitrite and even converted to nitrate.
The determination of various forms of nitrogen compounds in water helps to assess water contamination and “self-purificationâ€.
Fish are more sensitive to ammonia in water. When the ammonia nitrogen content is high, it can cause fish to die.
1. Method selection Ammonia nitrogen is usually determined by Nessler's colorimetric method, gas phase molecular absorption method, phenol-hypochlorite (or salicylic acid-hypochlorite) colorimetric method, and electrode method. Nessler's reagent colorimetric method is characterized by simple and sensitive operation. The metal ions such as calcium, magnesium and iron in water, sulfides, aldehydes and ketones, color, and turbidity all interfere with the determination and need to be pretreated accordingly. The phenolic chlorate colorimetric method has the advantages of being sensitive and stable, and the interference and elimination methods are the same as those of the Nessler reagent colorimetry. The electrode method has the advantages that there is usually no need for pretreatment of the water sample and a wide measurement range, but there are some problems with the life and reproducibility of the electrode. Gas-phase molecular absorption method is relatively simple, and special instruments or atomic absorption instruments can achieve good results. When the ammonia nitrogen content is high, distillation-acid titration may be used.
2. Preservation of water samples Water samples shall be collected in polyethylene or glass bottles and analyzed as soon as possible. If necessary, sulfuric acid may be added to acidify the samples to PH<2 and stored at 2～50C. Acidified samples should be protected against ammonia contamination in the air.
(I) Pretreatment of water samples
Water samples are colored or turbid and contain other substances that affect the determination of ammonia nitrogen. For this reason, appropriate pretreatments are required for analysis. For cleaner water, flocculation and sedimentation can be used; for polluted water or industrial wastewater, distillation is used to eliminate interference.
Flocculation and precipitation method Add appropriate amount of zinc sulfate to the water sample, and add sodium hydroxide to make it basic, generate zinc hydroxide precipitate, and then filter to remove color and turbidity.
1. Instrument: 100 stuffed cylinder or colorimetric tube.
2, reagent 110% zinc sulfate solution: Weigh 10 zinc sulfate dissolved in water, diluted to 100.
225% sodium hydroxide solution: Weigh 25 sodium hydroxide dissolved in water, diluted to 100, and stored in polyethylene bottles.
3 Sulfuric acid, Ï=1.84.
3. Steps Take 100ml of water sample in stoppered cylinder or colorimetric tube, add 1ml of 10% zinc sulfate solution and 0.1-0.2ml of 25% sodium hydroxide solution, adjust the pH to about 10.5, and mix. The precipitate was left to stand, filtered through a medium-speed filter paper thoroughly washed with ammonia-free water, and 20 ml of the primary filtrate was discarded.
Distilled water regulates the pH of the water sample so that it is in the range of 6.0 to 7.4. An appropriate amount of magnesium oxide is added to make it slightly acidic, and ammonia released by distillation is absorbed in the sulfuric acid or boric acid solution. When using Nessler's colorimetric method or acid titration method, boric acid solution is used as the absorbing solution; when using salicylic acid-hypochlorite colorimetric method, sulfuric acid solution is used as the absorbing solution.
1. Instrument: Nitrogen-adjusting distillation apparatus with nitrogen ball: 500-ml Kjeldahl flask, nitrogen ball, straight condensing tube and conduit, as shown in the figure.
2. Reagents: Ammonia-free water is used for dilution of the water sample and reagent configuration.
1) No ammonia preparation:
1 Distillation method: add 0.1 ml of sulfuric acid per liter of distilled water, redistill it in an all-glass distiller, discard 50 ml of initial sulfur liquid, and take in the remaining distillate in a glass jar with a mouthwash, and store it in a tampoon.
2 Ion exchange method: Distilled water is passed through a strongly acidic cation exchange resin column.
2) 1mol/L hydrochloric acid solution.
3) 1 mol/L sodium hydroxide solution.
4) Lightweight Magnesium Oxide: Magnesium oxide is heated at 500°C to remove carbonate.
5) 0.05% Bromophenol blue indicator solution (pH=6.0~7.6)
6) Anti-foaming agents, such as paraffin fragments.
7) Absorbent:
1 boric acid solution: Weigh 20g of boric acid dissolved in water and dilute to 1L.
2 sulfuric acid solution: 0.01mol/L.
Nessler's reagent photometric method
1. Method principle: The alkali solution of mercury iodide and potassium iodide reacts with ammonia to produce a reddish-brown colloidal compound, which has a strong absorption in a wide wavelength range. The measurement wavelength is usually in the range of 410 to 425 nm.2. Interfere with and eliminate organic compounds such as aliphatic amines, aromatic amines, aldehydes, acetone, hydrazines and organic chloramines, as well as inorganic ions such as iron, manganese, magnesium, and sulfur, which may cause interference due to the generation of a different color or turbidity. Color and turbidity also affect colorimetry. For this purpose, it must be subjected to flocculation precipitation filtration or distillation pretreatment, volatile interfering substances, and can also be heated under acidic conditions to remove. Interference with metal ions can be eliminated by adding an appropriate amount of masking agent.
3. Scope of application of the method The minimum detection concentration of this method is 0.025 mg/L (photometric method), and the upper limit of determination is 2 mg/L. Using visual colorimetry, the minimum detectable concentration was 0.02 mg/L. After appropriate treatment of water samples, the method can be applied to the determination of ammonia nitrogen in surface water, groundwater, industrial wastewater and domestic sewage.
4, instrument 1 spectrophotometer 2 pH meter 5, reagents: reagent water should be configured without ammonia 1) Nessler's reagent: You can choose one of the following methods to prepare.
1 Weigh 60g of potassium iodide and dissolve it in 100ml of water. Add a small amount of mercury dichloride (HgCl2) crystal powder (about 10g) while stirring until the vermilion precipitate does not dissolve easily. Add saturated mercury dichloride dropwise. Solution, and fully stirred, when there is little trace of red precipitation is not easy to dissolve, stop dropping mercury chloride solution.
Another 60g of potassium hydroxide was dissolved in water and diluted to 250ml. After sufficiently cooling to room temperature, the above solution was slowly poured into potassium hydroxide solution, diluted with water to 400ml, and mixed. Let stand overnight. The supernatant was transferred into a polyethylene bottle and stored in a stopper.
2 Weigh 16g of sodium hydroxide, dissolved in 50ml of water, and fully cooled to room temperature. Another said to take 7g of potassium iodide and 10g of mercury iodide (HgI2) dissolved in water, and then this solution was slowly injected into the sodium hydroxide solution under stirring, diluted with water to 100ml, stored in a polyethylene bottle, tampons preserved.
2) Potassium sodium tartrate solution: Dissolve 50g of sodium potassium tartrate (KNaC4H4O6? 4H2O) in 100ml of water, boil it to remove ammonia, let cool, and dilute to 100ml.
3) Ammonium standard stock solution: Weigh 3.819 g of superior pure ammonium chloride dried at 100°C and dissolve in water. Pipette into a 1000-volume flask and dilute to the mark. This solution is 1.00 mg ammonia nitrogen per ml.
4) Ammonium standard use solution: Pipette 5.00ml ammonium standard stock 500ml volumetric flask and dilute to the mark with water. This solution contains 0.010 mg of ammonia nitrogen per ml.
6. Steps (1) Drawing of the standard curve 1 Use 0, 0.5, 1.00, 3.00, 5.00, 7.00 and 10.0 ammonium standards.
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"Customer satisfaction" is our marketing purposes,so we have extensive experience in professional sales force,and strongly good pre-sale, after-sale service to clients. We can completely meet with customers' requirements and cooperate with each other perfectly to win the market.Sincerely welcome customers and friends throughout the world to our company,We strive hard to provide customer with high quality products and best service.
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