Ammonia nitrogen

Ammonia nitrogen ( NH3-N ) with free ammonia or ammonium salt ( NH3) ( NH4 + ) in water, their composition depends on the pH value of water. When the pH value is too high, a higher proportion of free ammonia. Conversely, the ammonium proportion is high.

The main sources of ammonia nitrogen in sewage of organic compounds containing nitrogen by microorganism decomposition products, some industrial wastewater, such as coking wastewater and ammonia fertilizer plant wastewater, as well as farmland drainage. In addition, in the anaerobic environment, water in the presence of the nitrite and the role of micro-organisms, reduction to ammonia. In aerobic environments, ammonia can be transformed into nitrite, and even continue to change into nitrate.

Determination of various forms of nitrogen compounds, contribute to the evaluation of water pollution and" self-purification" status.

High ammonia content, can be showed toxic effects on fish.

Method for the determination of a: Nessler s reagent colorimetric method ( GB7479--87)

The 1method

Mercuric iodide and potassium iodide alkaline solution and ammonia reaction of reddish brown colloidal compounds, this color in a wide wavelength range with strong absorption. Usually measuring wavelength in 410 - 425nm range.

The 2interference and elimination

Fatty amine, aromatic amine, aldehyde, acetone, alcohols and organic chloramines and other organic compounds, as well as iron, manganese, magnesium, sulfur and other inorganic ions, generated due to Harmonia or turbidity caused by interference, water color and turbidity were influenced by colorimetry. Therefore, through flocculation sedimentation filtration or distillation pretreatment, volatile reductive interference substance, but also in the acidic conditions of heating to remove. On the disturbance of metal ions, can be added to eliminate the masking agent.

3methodological suitable scope

The method of minimum detectable concentration is 0.025mol / L ( photometric method ), determination of upper bound for2mg / L. Using the visual colorimetry, the minimum detectable concentration is 0.02mg / L. Water samples for proper pretreatment, the method can be applied to surface water, groundwater, industrial wastewater and domestic sewage.

Instrument device

(1) spectrophotometric method.

(2) pH.

Test agent

Preparation of reagent water should be no ammonia.

1Nessler s reagent

Can select one of the following methods of preparation.

(1) said about 25ml20g potassium dissolving in water, stirring time added in small amounts to two mercuric chloride ( HgCI2) crystalline powder ( about 10g), to appear red precipitate insoluble, instead of dropping saturated two mercuric chloride solution, and fully stirred, when there is no trace red precipitate dissolution stop, drop and two mercuric chloride solution.

The other said60g potassium hydroxide dissolved in water, and diluted to250ml, cooling to room temperature, the solution in stir, pour in KOH solution, diluted with water to a 400ml, blending. Static night, supernatant into the polyethylene bottle, sealing plug preservation.

(2) with sodium hydroxide solution to16g,50ml is sufficiently cooled to room temperature.

The other said7g Ki and 10g mercuric iodide ( HgI2) dissolved in water, then the solution while stirring pour in sodium hydroxide solution, diluted with water to a 100ml, stored in polyethylene bottle, sealing plug preservation.

2potassium sodium tartrate solution

With50g potassium sodium tartrate ( KnaC4H4O64H2O100ml ) dissolved in water, boiled to remove ammonia, put cold, constant volume to 100ml.

3ammonium standard store solution

With3.819g by100 DEG C dried ammonium chloride ( NH4Cl ) dissolved in water, dilute to the mark. This solution per ml1.00mg containing ammonia nitrogen.

4ammonium standard solution

 Remove the5.00ml ammonium standard store solution in500ml volumetric flask, diluted with water to marking. This solution per ml0.010mg containing ammonia nitrogen.

Step step

1calibration curve

From0,0.50,1,3,5,7, and 10.0ml ammonium standard solution in50ml colorimetric tube, add to mark. With 1.0ml potassium sodium tartrate solution, mixing. 1.5ml Nessler s reagent, blending. After 10min placement, at a wavelength of4250nm, with the path 20mm cuvette, taking water as reference, measuring absorbance.

By measuring the absorbance of a minus zero concentration, the absorbance of blank tube, corrected absorbance, rendering to the ammonia nitrogen content (mg ) for correction of absorbance to the calibration curve.

Determination of2water samples

(1) divided by flocculation sedimentation amount after the pretreatment of water samples ( so that the ammonia nitrogen content of not more than 0.1mg ), joined the50ml colorimetric tube, diluted to mark, plus 1.0ml potassium sodium tartrate solution.

(2) divide the amount by distillation after pretreatment of the distillate, join 50ml colorimetric tube, and a quantitative 1mol / L NaOH solution to neutralize the acid, dilute to the mark. 1.5ml Nessler s reagent, blending. After 10min placement, with calibration curve step measuring absorbance.

Blank test: no ammonia instead of water, as a whole program blank determination.

From water samples measured absorbance of blank tests after subtracting the absorbance, from the calibration curve obtained ammonia nitrogen content ( mg ).

Ammonia nitrogen ( N, mg / L ) =

Type, M - by calibration curve to the ammonia nitrogen ( mg );

V - water ( ML ).

Precision and accuracy

In three laboratory analysis of1.14 ~ 1.16mg / L ammonia spiked water samples, the single laboratory relative standard deviation is less than 9.5%; and the recovery is in the range of 95~ 104%.

In four laboratory analysis of1.81 ~ 3.06mg / L ammonia spiked water samples, the single laboratory relative standard deviation is less than 4.4%; and the recovery is in the range of 94~ 96%.

Matters needing attention

(1) Nessler s reagent in mercuric iodide and potassium iodide proportion, color reaction sensitivity has a great influence on. Static after the formation of precipitation should be removed.

(2) paper often contain trace amounts of ammonium, note that when used with no ammonia washing. The glassware should avoid Laboratory of ammonia in air contamination.

 Two: methods for the determination of salicylate hypochlorous acid photometric method ( GB7481--87)

The generalizability of the

The 1method

In the presence of sodium nitroprusside, ammonium and salt of salicylic acid and hypochlorite ions reaction generates blue compound, at a wavelength of maximum absorption of 697nm.

The 2interference and elimination

Ammonium chloride under these conditions, were quantitative determination. Calcium, magnesium cation interference, plus potassium sodium tartrate masking.

3scope of application

 The method of minimum detectable concentration is 0.01mg / L,1mg / L determination of upper limit of. Suitable for drinking water, sewage and industrial wastewater determination of ammonia nitrogen in most.

Instrument device

(1) spectrophotometer.

(2) ( out of the liquid dropper dropper per ml, equivalent to 20+ 1drops)

Test agent

All reagents are used without ammonia water.

1ammonium standard store solution

With3.819g by100 DEG C dried ammonium chloride ( NH4Cl ) dissolved in water, into the1000ml volumetric flask, dilute to the mark. This solution per ml1.00mg containing ammonia nitrogen.

2standard intermediate liquid ammonium

Draw10.00ml ammonium standard stock solution removed100ml volumetric flask, dilute to the mark. This solution per ml0.10mg containing ammonia nitrogen.

3ammonium nitrate standard solution

Draw10.00ml ammonium standard intermediate liquid into the1000ml volumetric flask, dilute to the mark. The solution containing1 g per milliliter of ammonia nitrogen. Pro time configuration.

4color liquid

With50g salicylic acid ( C6H4( OH ) COOH ]100ml, adding water, adding160ml2mol / L NaOH solution, stirring to dissolve completely. The other said50g potassium sodium tartrate soluble in water, and the solution to merge into the1000ml volumetric flask, dilute to the mark. In brown glass bottle, the reagent is stable for at least a month.

Note: if the salicylic acid to dissolve, can add number ml sodium hydroxide solution, until completely dissolved, the final pH value of the solution for the6- 6.5.

In 5sodium hypochlorite solution

Take the market or to prepare sodium hypochlorite solution, after calibration, using sodium hydroxide solution containing available chlorine diluted to the concentration of 0.35% ( M / V ), free alkali concentration was 0.75mol / L (NaOH ) of sodium hypochlorite solution. Stored in a brown bottle, the reagent is stable for a week.

6solution of sodium nitroprusside

With0.1g sodium nitroprusside {Na2[ Fe ( CN )6NO )2H2O } in the10ml than the tube of color, soluble in water, dilute to the mark. This solution before clinical application preparation.

The 7 cleaning solution

With100g potassium hydroxide solution in100ml water, cooling and900ml 95% ( V / V ) ethanol mixed, stored in polyethylene bottle.

Step step

1calibration curve

From0,1,2,4,6,8.00ml ammonium standard solution in10ml colorimetric tube, diluted with water to join8ml,1.00mL color liquid and 2 drops of sodium nitroprusside solution, mixing. To drop2drops of sodium hypochlorite solution, dilute to the mark, full mixing. After 1h placement, at a wavelength of697nm, using optical path for 10mm cuvette, with water as the reference, the measured absorbance.

By measuring the absorbance of the blank tube, minus absorbance, corrected absorbance, rendering to the ammonia nitrogen content ( g ) to correct the absorbance of the calibration curve.

Determination of2water samples

Divide the amount of pretreated samples ( so that the ammonia nitrogen content of not more than8 g) to 10ml colorimetric tube, diluted with water to 8ml, calibration curves with the same operation, is used for color and measuring the absorbance.

3blank test

With no ammonia instead of water, according to samples were measured by the same steps for color and measurement.

Count count

From water samples measured absorbance of blank tests after subtracting the absorbance, from the calibration curve obtained ammonia nitrogen content ( g ).

Ammonia nitrogen ( N, mg / L ) =

Type, M - by calibration curve to the ammonia nitrogen ( g );

V - water ( ML ).

Matters needing attention

By using distilled water pretreatment, should with sulfuric acid solution as absorption liquid, color before the addition of sodium hydroxide solution to them and.