HJ 533-2009Ambient air exhaust gas. Determination of ammonia. Nesslerreagent spetcrophotometry (English PDF)

3.1 Metal ions such as trivalent iron

In the analysis, 0.50 ml of sodium potassium tartrate solution (4.6) was used to form a mask to eliminate the interference of metal ions such as ferric iron.

3.2 Sulfide

If the sample is disturbed by the occurrence of a heterochromatic color (such as green when the sulfide is present), dilute hydrochloric acid may be added to the sample solution to remove the dry matter.

Disturb.

3.3 Organics

Some organic substances (such as formaldehyde) produce precipitation interference measurement, and the absorption liquid can be used with 0.1 mol/L hydrochloric acid solution (4.7) before colorimetry.

Acidify to a pH not greater than 2 and then boil it.

4.1.1 Ion exchange method

The distilled water was passed through a column of strongly acidic cation exchange resin (hydrogen type), and the effluent was collected in a ground glass bottle. Per liter of effluent Add 10 g of strong acid cation exchange resin (hydrogen type) for easy storage.

4.1.2 Distillation method

0.1 ml of sulfuric acid (4.2) was added to 1 000 ml of distilled water and redistilled in a full glass distiller. Discard the first 50 ml of distillate, then Approximately 800 ml of distillate was then collected in a ground glass vial. 10 g of strong acid cation exchange resin (hydrogen) per liter of distillate collected Type), in order to save.

4.1.3 Water Purifier Method

Prepared with a commercially available water purifier before use.

4.2 Sulfuric acid, rho(H2SO4) = 1.84 g/ml.

4.3 Hydrochloric acid, rho(HCl) = 1.18 g/ml.

4.4 Sulfuric acid absorption solution, c(1/2H2SO4)=0.01 mol/L.

2.8 ml of sulfuric acid (4.2) was added to the water and diluted to 1 L to obtain a 0.1 mol/L stock solution. Dilute 10 times with water when it is ready.

4.5 Nessler Reagent

Weigh 12 g of sodium hydroxide (NaOH) dissolved in 60 ml of water and cool;

Weigh 1.7 g of mercury dichloride (HgCl2) dissolved in 30 ml of water;

Weigh 3.5 g of potassium iodide (KI) in 10 ml of water, and slowly add the above mercury dichloride solution to the potassium iodide solution while stirring.

Until the red precipitate formed is no longer dissolved;

Slowly add the sodium hydroxide solution cooled to room temperature to the above mixture of mercury dichloride and potassium iodide while stirring, and then add the remaining mercury dichloride solution was mixed and allowed to stand in the dark for 24 h. The supernatant was decanted, stored in a brown bottle, and stoppered with a rubber stopper, 2 to 5 °C can be stored for 1 month.

4.6 Potassium sodium tartrate solution, rho = 500 g/L.

Weigh 50 g of sodium potassium tartrate (KNaC4H6O6·4H2O) dissolved in 100 ml of water, heat and boil to drive off ammonia, and then cool to volume.

100 ml.

4.7 Hydrochloric acid solution, c (HCl) = 0.1 mol/L.

Take 8.5 ml of hydrochloric acid (4.3), add a certain amount of water, and dilute to 1 000 ml.

4.8 Ammonia standard stock solution, rho(NH3)=1 000 µg/ml.

Weigh 0.785 5 g of ammonium chloride (NH4Cl, pure grade, dried at 100-105 ° C for 2 h), dissolve in water, and transfer to a 250 ml volumetric flask.

Dilute to the mark with water.

4.9 Ammonia standard use solution, rho(NH3)=20 µg/ml.

Pipette 5.00 ml of ammonia standard stock solution (4.8) into a 250 ml volumetric flask, dilute to volume, and shake well. Prepare before use.

6.1 Preparation of sampling tube

The absorbent tube with good air tightness, resistance and absorption efficiency should be cleaned and dried for use. Fill the absorbent and seal it before sampling Keep away from light.

6.2 Sample Collection

The sampling system consists of a sampling tube, a drying tube and a gas sampling pump. Sampling should be carried out with a full blank absorbing tube.

Ambient air sampling. Collect with a 10 ml absorption tube at a flow rate of 0.5 to 1 L/min for at least 45 minutes.

Industrial waste gas sampling. Use a 50 ml absorption tube to collect at a flow rate of 0.5 to 1 L/min. The gas collection time depends on the specific conditions. If industry when the temperature of the exhaust gas (such as flue gas) is significantly higher than the ambient temperature, the sampling line should be heated to prevent condensation of flue gas in the sampling line.

6.3 Sample storage

It should be analyzed as soon as possible after sampling to prevent absorption of ammonia from the air. If it can not be analyzed immediately, it can be stored for 7 days at 2~5 °C.

7.1 Drawing a calibration curve

Take 7 10 ml plug color tubes and prepare a standard series according to Table 1.

Table 1 Standard series

Pipe number 0 1 2 3 4 5 6 Standard solution (4.9)/ml 0.00 0.10 0.30 0.50 1.00 1.50 2.00 Water/ml 10.00 9.90 9.70 9.50 9.00 8.50 8.00 Ammonia content/µg 0 2 6 10 20 30 40 Accurately remove the corresponding standard volume of liquid (4.9) according to Table 1, add water to 10 ml, and add 0.50 ml of potassium tartrate to each tube.

Sodium solution (4.6), shake well, then add 0.50 ml of Nessler reagent (4.5) and shake well. After 10 minutes of placement, at a wavelength of 420 nm, the absorbance was measured using a 10 mm cuvette with water as a reference. Taking the ammonia content (µg) as the abscissa, the absorbance of the reagent blank is taken as the vertical sitting Draw a calibration curve.

7.2 Sample determination

Take a certain amount of sample solution (depending on the sample concentration) in a 10 ml colorimetric tube and dilute to 10 ml with the absorption solution (4.4).

Add 0.50 ml of sodium potassium tartrate solution (4.6), shake well, add 0.50 ml of Nessler's reagent (4.5), shake well, leave for 10 min, then the absorbance was measured at a wavelength of 420 nm using a 10 mm cuvette with water as a reference.

7.3 Blank test

7.3.1 Absorbent blank. Replace the sample with the absorbent prepared in the same batch as the sample and measure the absorbance according to 7.2.

7.3.2 Sampling the whole process blank. the corresponding volume of the absorption liquid prepared in the same batch as the sample is added to the sampling tube and brought to the sampling site.

For the sampled absorbent, measure the absorbance according to 7.2.

10.1 Inspection without ammonia

Replace the sample with water. Measure the absorbance according to 7.2. The blank absorbance value should not exceed 0.030 (10 mm cuvette), otherwise check the water and the purity of the reagent.

10.2 Sampling full blank

It is used to check whether the sample is contaminated during sample collection, transportation and storage. If the sampling blank is significantly higher than the same batch of suction when the liquid is blank, the samples collected in the same batch are discarded.

10.3 Preparation of Nessler's reagent

In order to ensure good color development of Nessler's reagent, it is necessary to control the amount of HgCl2 added during the preparation, until the trace amount of HgI2 is not precipitated.

Soon when dissolved. The ratio of HgCl2 to KI required to prepare 100 ml of the Nessler reagent is about 2.3.5. In order to speed up the reaction during preparation Speed, saving preparation time, can be heated at low temperature to prevent the early precipitation of HgI2 red precipitate.

10.4 Preparation of potassium sodium tartrate

When the ammonium salt of sodium potassium tartrate reagent is high, only the boiling of the boiling or the precipitation of the drug is not completely removed. At this time, use less to join the amount of sodium hydroxide solution is boiled to remove 20% to 30% of the volume of the solution, and after cooling, it is diluted to the original volume with ammonia-free water.

10.5 Proper use of the sampling pump

Before turning on the sampling pump, confirm that the sampling system is connected correctly. The inlet end of the sampling pump passes through the drying tube (or buffer tube) and the sampling tube.

The gas outlets are connected, and if they are reversed, the acid absorption liquid will be sucked up, contaminating and damaging the instrument. In case of reverse suction, the flow should be timely Remove it, wash it with alcohol, dry it, and reinstall it. Continue to use it after passing the flow calibration.

10.6 Prevent the sampling tube from being contaminated

In order to avoid contamination of the absorption liquid in the sampling tube, do not tilt or invert the sampling tube during transportation and storage, and replace the sampling tube in time.

Seal the joint.