HJ 534-2009Ambient air. Determination of ammonia. Sodium hypochlorite-salicylic acid spectrophotometry (English PDF)

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 Sulfuric acid absorption liquid, c(1/2 H2SO4)=0.005 mol/L.

2.8 ml of sulfuric acid (4.2) was added to the water and diluted to 1 L to obtain a stock solution of 0.1 mol/L. Dilute 20 times when it is ready.

4.4 Salicylic acid-sodium potassium tartrate solution

Weigh 10.0 g of salicylic acid [C6H4(OH)COOH] in a 150 ml beaker, add appropriate amount of water, and add 5 mol/L sodium hydroxide solution.

15 ml, stir to dissolve completely. Also weigh 10.0 g of sodium potassium tartrate (KNaC4H6O6·4H2O), dissolved in water, heated to boil the ammonia was removed, and after cooling, it was combined with the above solution and transferred to a.200 ml volumetric flask, diluted with water to the mark, and shaken. The pH of this solution is 6.0~ 6.5, stable in brown bottles at 2 to 5 ° C for 1 month.

4.5 sodium nitroferricyanide solution, rho = 10 g/L.

Weigh 0.1 g of sodium nitrosodium ferricyanide {Na2[Fe(CN)6NO]·2H2O}, place it in a 10 ml plug colorimetric tube, add water to dissolve it, Constant volume to the marking line, ready to use.

4.6 Sodium hypochlorite

Commercial reagents can be purchased, or they can be prepared by themselves. For detailed preparation methods, see Appendix A.1.

Sodium hypochlorite solution (stock solution) stored in plastic bottles, the effective chlorine concentration and free alkali concentration should be calibrated before each use (with NaOH) for the calibration method, see Appendix A.2 and Appendix A.3.

4.7 sodium hydroxide solution, c (NaOH) = 2 mol/L.

Weigh 8.0 g of sodium hydroxide and dissolve in 100 ml of water.

4.8 sodium hypochlorite use solution, rho (effective chlorine) = 3.5 g/L, c (free base) = 0.75 mol/L.

Take appropriate amount of calibrated sodium hypochlorite (4.6), dilute with water and 2 mol/L sodium hydroxide solution (4.7) to contain the effective chlorine concentration 3.5 g/L, sodium hypochlorite use solution with a free base concentration of 0.75 mol/L (as NaOH) (calculated the required dilution ratio based on the calibration results) the number or the volume of sodium hydroxide that needs to be added is stored in a brown dropper bottle. This reagent is stable for 1 week.

4.9 Standard stock solution of ammonium chloride, rho = 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 and store at 2 to 5 ° C for 1 month.

4.10 Standard use solution of ammonium chloride, rho=10 µg/ml.

Pipette 5.0 ml of ammonium chloride standard stock solution (4.9) in a 500 ml volumetric flask and dilute to the mark with water.

6.1 Preparation of the absorption 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 drying tube (5.5), an absorption tube and a gas sampling pump with 10 ml of absorption liquid (4.3). When sampling Sampling the entire blank sampling tube.

Smell source plant sampling. at a flow rate of 1.0 L/min, gas production is 1 to 4 L. Pay attention to the wind direction under the source of malodor, and capture the stench.

A sample of the time.

Ambient air sampling. gas production at a flow rate of 0.5 to 1.0 L/min for at least 45 minutes.

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 standard curve

Take 7 plugs of 10 ml colorimetric 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 (4.10)/ml 0.00 0.20 0.40 0.60 0.80 1.00 1.20 Ammonia content/µg 0.0 2.0 4.0 6.0 8.0 10.0 12.0 Dilute each tube to 10 ml with water, add 1.00 ml of salicylic acid-sodium potassium tartrate solution (4.4), and 2 drops of sodium nitroferricyanide solution.

(4.5), 2 drops of sodium hypochlorite use solution (4.8), shake and place for 1 h. Use a 10 mm cuvette at a wavelength of 697 nm with water as a reference.

The absorbance was measured. The standard curve was drawn by taking the absorbance of the reagent blank as the ordinate and the ammonia content (µg) as the abscissa.

7.2 Sample determination

After sampling, add appropriate amount of water and bring the sample solution to a volume of 10 ml. Accurately draw a certain amount of sample solution (the amount of suction depends on the concentration of the sample) in a 10 ml colorimetric tube, dilute to 10 ml with the absorption solution (4.3), add 1.0 ml of salicylic acid-sodium potassium tartrate solution (4.4), 2 drops Sodium nitroferricyanide solution (4.5), 2 drops of sodium hypochlorite solution (4.8), shake and place for 1 h. Use a 10 mm cuvette at a wavelength of 697 at nm, the absorbance was measured using water as a reference.

7.3 Blank test

7.3.1 Absorbent blank. Replace the sample with an 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 Proper use of the sampling pump

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

The mouth is connected, if it is reversed, it will cause the acid absorption liquid to suck up, pollute and damage the instrument. In case of reverse suction, the flowmeter should be dismantled in time.

Wash it down, dry it with alcohol, reinstall it, and continue to use it after passing the flow calibration.

10.4 Preventing the absorption tube from being contaminated

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

Seal the joint.

Appendix A

(normative appendix) Preparation method of sodium hypochlorite solution and calibration of available chlorine concentration and free alkali concentration A.1 Preparation method of sodium hypochlorite solution Hydrochloric acid (rho=1.19 g/L) was applied dropwise to the potassium permanganate solid, and the evolved chlorine gas was introduced into the 2 mol/L sodium hydroxide absorption liquid.

Collect, produce a pale green green sodium hypochlorite solution and store in a plastic bottle. Since the solution is unstable, its available chlorine concentration should be calibrated before use.

A.2 Determination of available chlorine content in sodium hypochlorite solution Pipette 10.0 ml sodium hypochlorite (4.6) into a 100 ml volumetric flask, dilute with water to the mark, and mix. Pipette 10.0 ml of diluted Sodium hypochlorite solution in a 250 ml iodine measuring flask, add 40 ml of distilled water, 2.0 g of potassium iodide, and mix. Add 6 mol/L sulfuric acid solution 5 Ml, dense, mix. After 5 min in the dark, add 0.10 mol/L sodium thiosulfate solution to pale yellow, add about 1 ml starch indication.

Continue to drop until the blue color disappears. Its effective chlorine concentration is calculated according to formula (A.1).

Available chlorine (g/L, in Cl2) = 35.45 10010.0 10 c V× × × (A.1) where. c--concentration of sodium thiosulfate solution, mol/L;

V--titration consumption volume of sodium thiosulfate solution, ml;

35.45 - molar mass of available chlorine (1/2 Cl2), g/mol.

Determination of free base (as NaOH) in A.3 sodium hypochlorite solution A.3.1 Calibration of hydrochloric acid solution Sodium carbonate standard solution. c (1/2Na2CO3) = 0.100 0 mol/L. Weighed anhydrous sodium carbonate 2.650 0 g dried at 180 ° C for 2 h, dissolved in freshly boiled cold water, transfer to a 500 ml volumetric flask and dilute to the mark.

Methyl red indicator. rho = 0.5 g/L. 50 mg of methyl red was weighed and dissolved in 100 ml of ethanol (rho = 0.99 g/ml).

Hydrochloric acid standard titration solution. c (HCl) = 0.10 mol/L. Take 8.5 ml of hydrochloric acid (rho=1.19 g/L) in a 1 000 ml volumetric flask with water Dilute to the mark. Calibration method. Pipette 25.00 ml sodium carbonate standard solution into a 150 ml vertebra bottle, add 25 ml water and 1 drop of methyl red the indicator was titrated to a reddish color with a standard hydrochloric acid titration solution. Calculate the concentration of the hydrochloric acid standard solution using formula (A.2).

1 1(HCl) c Vc

Where. c--hydrochloric acid standard titration solution concentration, mol/L;

C1--sodium carbonate standard solution concentration, mol/L;

V1--sodium carbonate standard solution volume, ml;

V2--HCl standard titration solution volume, ml.

A.3.2 Determination of free alkali (calculated as NaOH) in sodium hypochlorite solution Pipette sodium hypochlorite (4.6) 1.0 ml into a 150 ml Erlenmeyer flask, add 20 ml of water, use phenolphthalein as an indicator, and use 0.10 mol/L salt.

The acid standard titration solution is titrated until the red color completely disappears. If the color change at the end point is not obvious, add 1 drop of phenol to the titrated solution.

indicator, if the color is still red, continue to use a standard hydrochloric acid titration solution to drop to colorless.

Free base concentration (mol/L, in NaOH) = (HCl) (HCl) cv × (A.3) where. c (HCl) - concentration of hydrochloric acid standard solution, mol/L;

v(HCl)--the volume of hydrochloric acid solution consumed by titration, ml;

V - the volume of sodium hypochlorite solution taken by titration, ml.