HJ 483-2009Ambient air. Determination of sulfur dioxide. Tetrachloromercurate(TCM)-pararosaniline method (English PDF)

Foreword

To protect the environment and protect people in order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on the Prevention and Control of Air Pollution this standard is established for the determination of sulfur dioxide in ambient air.

This standard specifies the tetrachloromercury absorption-pararosaniline spectrophotometric method for the determination of sulfur dioxide in ambient air.

This standard is for the determination of air quality of sulfur dioxide, tetrachloromercury salt - pararosaniline hydrochloride colorimetric method (GB/T 8970-88) Revision.

This standard was first published in 1988, and the original standard drafting unit was the Beijing Environmental Protection Monitoring Center. This is the first revision.

The main revisions are as follows.

-- Change the name of the standard to "Determination of Ambient Air Sulphur Dioxide - Tetrachloromercury Salt Absorption - Pararosaniline Spectrophotometry";

- increased the content of the warning;

- clarify the standard detection limits and measurement range;

- Increased the number of times the standard solution is calibrated in parallel;

-- Added field blank test;

--Improved the calculation formula for the concentration of sodium thiosulfate solution and the determination result of sulfur dioxide in air;

-- Added quality assurance and quality control provisions, specified requirements for the quality of the absorption tube of the porous glass plate; emphasized the effect of temperature on sampling the effect of the rate; the requirement for the slope of the calibration curve is relaxed;

-- Added waste disposal provisions.

From the date of implementation of this standard, the national environmental protection standard "Air" approved and issued by the former National Environmental Protection Agency on March 26, 1988.

Determination of quality sulphur dioxide The tetrachloromercury salt-para-rosaniline hydrochloride colorimetric method (GB 8970-88) is abolished.

This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.

This standard is mainly drafted by. Shenyang Environmental Monitoring Center Station.

This standard was approved by the Ministry of Environmental Protection on September 27, 2009.

This standard has been implemented since November 1, 2009.

This standard is explained by the Ministry of Environmental Protection.

Determination of ambient air sulfur dioxide Tetrachloromercury salt absorption-pararosaniline spectrophotometry Warning. Potassium tetrachloromercurate solution is a highly toxic reagent. When operating, wear protective equipment as required to avoid contact with skin and clothing.

The preparation of the quasi-solution should be carried out in the fume hood; the residual residue after the test should be properly and safely disposed.

1 Scope of application

This standard specifies the tetrachloromercury absorption-pararosaniline spectrophotometric method for the determination of sulfur dioxide in air.

This standard applies to the determination of sulfur dioxide in ambient air.

When 5 ml of absorption solution is used and the sampling volume is 30 L, the detection limit of sulfur dioxide in the air is determined to be 0.005 mg/m3.

The limit is 0.020 mg/m3 and the upper limit of determination is 0.18 mg/m3.

When 50 ml of absorption solution is used and the sampling volume is 288 L, the detection limit of sulfur dioxide in the air is determined to be 0.005 mg/m3.

The lower limit is 0.020 mg/m3 and the upper limit of determination is 0.19 mg/m3.

2 Principle of the method

After the sulfur dioxide is absorbed by the potassium tetrachloromercurate solution, a stable dichlorosulfite complex is formed, which is then reacted with formaldehyde and pararosaniline hydrochloride.

Use to generate a purple-red complex and measure the absorbance at 575 nm.

3 Interference and elimination

The main interferents of the method are nitrogen oxides, ozone, manganese, iron, chromium and the like. The addition of ammonium sulfamate eliminates the interference of nitrogen oxides;

After the sample is placed for a period of time, the ozone can be decomposed by itself; adding phosphoric acid and ethylenediaminetetraacetic acid disodium salt can eliminate or reduce certain heavy metals.

Ion interference.

4 Reagents and materials

Analytically pure reagents that meet national standards are used for analysis, and experimental water is newly prepared distilled water or equivalent purity unless otherwise stated.

Water.

4.1 Potassium iodate (KIO3), excellent grade, dried at 110 ° C for 2 h.

4.2 Potassium iodide (KI).

4.3 Glacial acetic acid (CH3COOH).

4.4 Potassium tetrachloromercury (TCM) absorption solution, c(TCM)=0.04 mol/L. Weigh 10.9 g of mercury dichloride, 6.0 g of potassium chloride and 0.070 g of B Diamine tetraacetic acid disodium salt (EDTA-2Na) was dissolved in water and diluted to 1 L. This solution is stored in a closed container and is stable for 6 months.

If precipitation is found, it can not be reused.

4.5 Formaldehyde solution, rho (HCHO) ~ 2 g/L. Measure 1 ml 36% ~ 38% (mass fraction) formaldehyde solution, diluted to.200 ml, use Now available.

4.6 Ammonium sulfamate solution, rho (H2NSO3NH4) = 6.0g/L. Weigh 0.60 g of ammonium sulfamate dissolved in 100 ml of water, ready for use.

4.7 Iodine stock solution, c(1/2 I2)=0.10 mol/L. Weigh 12.7 g of iodine (I2) in a beaker, add 40 g of potassium iodide and 25 ml of water, stir Stir until completely dissolved, dilute to 1 000 ml with water, and store in a brown bottle.

4.8 Iodine solution, c(1/2 I2)=0.010 mol/L. Take iodine stock solution (4.7) 50 ml, dilute with water to 500 ml, store in brown fine mouth in the bottle.

4.9 Starch solution, rho (starch) = 5.0 g/L. Weigh 0.5 g of soluble starch in a 150 ml beaker and make a paste with a small amount of water.

Slowly pour 100 ml of boiling water, continue to boil until the solution is clear, cool and store in the reagent bottle.

4.10 potassium iodate reference solution, c (1/6 KIO3) = 0.100 0 mol/L. accurately weigh 3.566 7 g potassium iodate (4.1) dissolved in water, moved into in a 1 000 ml volumetric flask, dilute with water to the mark and shake.

4.11 Hydrochloric acid solution, c (HCl) = 1.2 mol/L. Measure 100 ml of concentrated hydrochloric acid and add to 900 ml of water.

4.12 Standard stock solution of sodium thiosulfate, c(Na2S2O3)=0.10 mol/L. Weigh 25.0 g of sodium thiosulfate (Na2S2O3·5H2O), dissolve in 1 000 ml of freshly boiled but cooled water, add 0.2 g of anhydrous sodium carbonate, store in a brown jar, and set aside for one week. Such as the solution appeared cloudy and must be filtered.

Calibration method. Pipette three portions of 20.00 ml potassium iodate reference solution (4.10) into a 250 ml iodine flask and add 70 ml of new boil.

However, the cooled water, add 1 g of potassium iodide, shake until completely dissolved, add 10 ml of hydrochloric acid solution (4.11), immediately cover the stopper and shake.

After placing in the dark for 5 min, titrate the solution with sodium thiosulfate standard solution (4.12) to pale yellow, add 2 ml of starch solution (4.9), followed by Continue to titrate until the blue color just fades to the end. The concentration of sodium thiosulfate standard solution is calculated according to formula (1).

0.100 0 20.00

Where. c1--sodium thiosulfate standard solution concentration, mol/L;

V--Titration of the volume of sodium thiosulfate standard solution consumed, ml.

4.13 Sodium thiosulfate standard solution, c(Na2S2O3) ~0.010 00 mol/L. Take 50.0 ml of sodium thiosulfate stock solution (4.12) Dilute to the mark with freshly boiled but cooled water in a 500 ml volumetric flask and shake well.

4.14 Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) solution, rho (EDTA-2Na)=0.50 g/L. Weigh 0.25 g of ethylenediaminetetraacetic acid the sodium salt [C10H14N2Na2O8·2H2O] is dissolved in 500 ml of freshly boiled but cooled water. Available at the time of use.

4.15 sodium sulfite solution, rho (Na2SO3) = 1 g/L. weigh 0.2 g sodium sulfite (Na2SO3), dissolved in.200 ml EDTA-2Na (4.14) in the solution, slowly shake to prevent oxygenation and dissolve. After 2 to 3 hours, it is calibrated. This solution is equivalent to 320-400 µg of dioxane per milliliter Sulfur.

Calibration method.

a. Take 6 250 ml iodine bottles (A1, A2, A3, B1, B2, B3) and add 25 ml of ethylenediamine tetraethylene in A1, A2 and A3.

Acid di-sodium salt solution (4.14), add 25.00 ml of sodium sulfite solution (4.15) in B1, B2, B3, respectively, add 50.0 ml of iodine solution Liquid (4.8) and 1.00 ml glacial acetic acid, cover the cap and shake well.

b. Immediately pipette 2.00 ml of sodium sulfite solution (4.15) to a solution containing 40 to 50 ml of potassium tetrachloromercury (4.4).

In a 100 ml volumetric flask, dilute to the mark with tetrachloromercury potassium absorbing solution (4.4) and shake well. This solution is the standard storage of sulfur dioxide.

liquid.

c.A1, A2, A3, B1, B2, B3 Six bottles are placed in the dark for 5 min, then titrated to a light yellow with sodium thiosulfate solution (4.13) Color, add 5 ml of starch indicator (4.9), continue to titrate until the blue color just disappears. The difference in volume of sodium thiosulfate solution used for parallel titration should be not more than 0.05 ml.

The mass concentration of the standard storage solution of sulfur dioxide (4.15 b) is calculated according to formula (2).

rho (SO2)=

0 2( ) 32.02 10 2.00 25.00 100 VV c- × × × × (2) where. rho (SO2) - the concentration of sulfur dioxide standard stock solution (4.15 b), µg/ml;

0V - the average volume of sodium thiosulfate solution (4.13) used for blank titration, ml;

V - the average volume of sodium thiosulfate solution (4.13) used for sample titration, ml;

The concentration of c2--sodium thiosulfate solution (4.13), mol/L.

4.16 Sulfur dioxide standard solution, rho (SO2)=2.00 µg/ml. Standard storage solution of sulfur dioxide with tetrachloromercury potassium absorption solution (4.15 b) Dilute to a standard solution containing 2.0 µg of sulfur dioxide per ml. This solution is used to draw a standard curve and is refrigerated at 4 to 5 ° C to stabilize 20 d.

4.17 Pararosaniline hydrochloride (referred to as PRA, ie, sub-magenta or magenta) stock solution. rho (PRA) = 2 mg/ml.

Its purity should meet the quality requirements of the purification and testing methods of para-rosaniline (see Appendix A).

4.18 Phosphoric acid solution, c(H3PO4) = 3 mol/L. Take 41 ml of 85% concentrated phosphoric acid (rho = 1.69 g/ml) and dilute to.200 ml with water.

4.19 Pararosaniline hydrochloride (PRA) use solution. rho (PRA) = 0.16 mg/ml.

Pipette the PRA stock solution (4.17) 20.00 ml into a 250 ml volumetric flask, add.200 ml of phosphoric acid solution (4.18), and dilute with water until Marking. It can be used for at least 24 hours and stored in the dark for 9 months.

5 Instruments and equipment

5.1 Spectrophotometer (visible wavelength 380 ~ 780 nm).

5.2 Porous glass plate absorption tube. 10 ml porous glass plate absorption tube for short time sampling; 50 ml porous glass plate absorption bottle for 24 h connection Continue sampling.

5.3 Constant temperature water bath. 0 ~ 40 ° C, control accuracy is ± 1 ° C.

5.4 with colorimetric tube. 10 ml.

Used cuvettes and cuvettes should be dip in a timely manner with a mixture of hydrochloric acid (14) and ethanol (95%) (both in a volume ratio of 3.1) Wash, otherwise the red is difficult to wash.

5.5 Air sampler.

Air sampler for short-time sampling with a flow range of 0.1 to 1 L/min. The sampler for 24 h continuous sampling should have a constant temperature, Constant current, timing, automatic control instrument switch function, flow range 0.1 ~ 0.5 L/min.

5.6 Common instruments in general laboratories.

6 Samples

6.1 Short-time sampling. a porous glass plate absorption tube containing 5.0 ml of potassium tetrachloromercurate absorption solution (4.4), and a gas flow rate of 0.5 L/min.

10 to 30 L, the temperature of the absorption liquid is maintained in the range of 10 to 16 °C.

6.2 Continuous 24 h sampling. a porous glass plate absorption tube containing 50 ml of potassium tetrachloromercury absorbing solution (4.4), with a gas flow rate of 0.2 L/min at 288 L, the temperature of the absorbent is maintained in the range of 10 to 16 °C.

6.3 Field blank. Take the sampling tube with the absorption liquid to the sampling site. Except for no gas production, the other environmental conditions are the same as the sample.

7 Analysis steps

8 Results are expressed

The mass concentration of sulfur dioxide in the air is calculated according to formula (3).

(SO ) t

AA a V

b VV

rho - -= ×× (3)

Where. rho (SO2)--the mass concentration of sulfur dioxide in the air, mg/m3;

A--the absorbance of the sample solution;

A0--the absorbance of the reagent blank solution;

B--the slope of the standard curve;

A--the intercept of the standard curve, absorbance/µg;

Vt--the total volume of the sample solution, ml;

Va--the volume of the sample solution taken during the measurement, ml;

Vs--converted to the standard sample size (101.325 kPa, 273 K), L.

The calculation result should be accurate to the third decimal place.

9 Precision and accuracy

17 laboratories analyzed spiked gas samples containing 0.9 to 1.2 µg/ml of sulfur dioxide (after collecting atmospheric samples with potassium tetrachloromercurate absorption solution) Adding sulfur dioxide standard solution), the relative standard deviation of a single laboratory does not exceed 9.0%, and the spiked recovery rate is 93% to 111%.

Eighteen laboratories analyzed sulfur dioxide containing 4.8 to 5.0 µg/ml of spiked gas sample, and the relative standard deviation of individual laboratories did not exceed 6.6%, the recovery rate of the standard addition is 94% to 106%.

10 Quality Assurance and Quality Control

10.1 The resistance of the absorption tube of the porous glass plate is 6.0 kPa±0.6 kPa, and the 2/3 glass plate area is evenly foamed, and no air bubbles escape at the edges.

10.2 The temperature of the absorption liquid at the time of sampling is controlled at 10 to 16 °C.

10.3 At least two field blanks are to be determined for each batch of samples. Bring the sampling tube with the absorption liquid to the sampling site, except that it does not collect gas.

His environmental conditions are the same as the samples. Direct sunlight should be avoided during sample collection, transportation and storage. If the sample cannot be analyzed on the same day, it should be stored at 4~5 °C, but the storage time should not exceed 7 days.

10.4 When the concentration of sulfur dioxide in the air is higher than the upper limit of measurement, the sampling volume may be appropriately reduced or the volume of the sample may be reduced. If sample the absorbance of the solution exceeds the upper limit of the standard curve, and can be diluted with the reagent blank, and the absorbance is measured within a few minutes, but the dilution factor is not Greater than 6.

10.5 The color temperature is low, the color development is slow, and the stabilization time is long. The color temperature is high, the color development is fast, and the stabilization time is short. The operator must understand the color the relationship between temperature, color development time and settling time is strictly controlled. The temperature at which the sample is measured and the temperature at which the calibration curve is drawn the difference should not exceed 2 °C.

10.6 The slope of the calibration curve is between 0.073 and 0.082 under the given conditions. The reagent blank absorbance A0 and the drawing standard are determined when the sample is measured.

The A0 fluctuation range of the curve does not exceed ±15%.

10.7 Hexavalent chromium can cause the purple-red complex to fade and cause negative interference, so avoid washing the glassware with sulfuric acid-chromic acid wash. If used After the sulfuric acid-chromic acid washing solution has been washed, it is washed with a hydrochloric acid solution (1 1) and thoroughly washed with water.

11 Waste treatment

In the detected waste liquid of potassium tetrachloromercurate, about 10 g of sodium carbonate per liter is added to neutral, and 10 g of zinc particles are added. Stir under a black cloth cover for 24 h After that, the supernatant was poured into a glass jar, and a saturated sodium sulfide solution was added dropwise until no precipitation occurred. Discard the solution and transfer the precipitate to the appropriate in the container. This method removes 99% of the mercury in the waste stream.

Appendix A

(informative appendix) Purification and test method of pararosaniline hydrochloride A.1 reagent A.1.1 n-butanol A.1.2 Glacial acetic acid A.1.3 hydrochloric acid solution. c (HCl) = 1 mol/L A.1.4 Acetic acid-sodium acetate solution. c(CH3COONa)=1.0 mol/L Weigh 13.6 g of sodium acetate (CH3COONa·3H2O) dissolved in water, transfer to a 100 ml volumet...