HJ 479-2009Ambient air. Determination of nitrogen oxides. N-(1-Naphthyl) ethylene diamine dihydrochloride spectrophotometric method (English PDF)

Foreword

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 Atmospheric Pollution this standard is established for human health and the determination of nitrogen oxides in ambient air.

This standard specifies methods for determining nitrogen oxides (nitrogen monoxide and nitrogen dioxide) in ambient air.

This standard is for the determination of air quality nitrogen oxides, naphthylamine diamine colorimetric method (GB 8969-88) and ambient air.

The determination of nitrogen oxides was carried out by the Saltzman method (GB/T 15436-1995).

"Determination of Air Quality Nitrogen Oxide Determination of Naphthylethylenediamine Hydrochloride" (GB 8969-88) was first published in 1988.

The quasi-drafting unit is the Beijing Environmental Monitoring Center; the first is the Salttzman Method for the Determination of Nitrogen Oxides in the Ambient Air (GB/T 15436-1995) it was released in 1995, and the original standard drafting unit was the Shenyang Environmental Monitoring Center Station. This is the first revision.

The main revisions are as follows.

-- Revised the name and scope of the standard;

-- Improve the textual content of the standard method principle;

- Defining the amount of potassium permanganate and barium hydroxide used in the preparation of experimental water;

-- Increased interference and elimination clauses and sample retention terms;

- Refined the analysis steps and increased the blank test requirements;

-- Eliminated the second book "Soxidation" in the Saltzman Method for the Determination of Nitrogen Oxides in Environmental Air (GB/T 15436-1995) Chromium-quartz sand oxidation method.

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 mass nitrogen oxides - Naphthylethylenediamine hydrochloride colorimetric method (GB 8969-88) and former National Environmental Protection Agency March 25, 1995 National Environmental Protection Standards for the Determination and Determination of Environmental Air Nitrogen Oxides by the National Standard for Environmental Protection (GB/T 15436-1995) Abolished.

Appendix A of this standard is a normative appendix, and Appendix B is an informative appendix.

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 NOx (nitrogen monoxide and nitrogen dioxide) Naphthylethylenediamine hydrochloride spectrophotometry

1 Scope of application

This standard specifies the spectrophotometric method for the determination of nitrogen oxides in ambient air.

This standard applies to the determination of nitrogen oxides, nitrogen dioxide and nitrogen monoxide in ambient air.

The method detection limit of this standard is 0.12 µg/10 ml of absorption liquid. When the total volume of the absorption liquid is 10 ml and the sampling volume is 24 L, it is empty.

The detection limit of nitrogen oxides in the gas is 0.005 mg/m3. When the total volume of the absorbent is 50 ml and the sampling volume is 288 L, the nitrogen oxides in the air the detection limit was 0.003 mg/m3. When the total volume of the absorbent is 10 ml and the sampling volume is 12 to 24 L, the nitrogen oxides in the ambient air the measurement range is from 0.020 to 2.5 mg/m3.

2 Terms and definitions

3 Principle of the method

Nitrogen dioxide in the air is absorbed by the absorption liquid in the first absorption bottle in series and reacts to form a pink azo dye. One in the air Nitric oxide does not react with the absorption liquid, and is oxidized to the nitrogen dioxide by the acidic potassium permanganate solution through the oxidation tube, and is connected in the second absorption bottle in series.

The absorption liquid absorbs and reacts to form a pink azo dye. The absorbance of the generated azo dye at a wavelength of 540 nm and the content of nitrogen dioxide the amount is proportional. The absorbances of the samples in the first and second absorption bottles were measured, and the nitrogen dioxide and nitrogen monoxide in the two absorption bottles were calculated.

The mass concentration, the sum of the two is the mass concentration of nitrogen oxides (in terms of NO2).

4 Reagents and materials

Unless otherwise stated, analytically pure reagents and nitrite-free distilled water in accordance with national or professional standards are used for analysis.

Sub-water or water of considerable purity. If necessary, experimental water can be added to 0.5 g of potassium permanganate (KMnO4) per liter of water in a full glass distiller.

And steamed with 0.5 g of barium hydroxide [Ba(OH)2].

4.1 Glacial acetic acid.

4.2 Hydroxylamine hydrochloride solution, rho = 0.2 ~ 0.5 g/L.

4.3 sulfuric acid solution, c (1/2H2SO4) = 1 mol/L. take 15 ml of concentrated sulfuric acid (rho20 = 1.84 g/ml), slowly added to 500 ml of water, stir Evenly, cool for later use.

4.4 Acidic potassium permanganate solution, rho (KMnO4)=25 g/L. Weigh 25g potassium permanganate in a 1 000 ml beaker and add 500 ml of water.

Slightly heat to dissolve all of them, then add 1 ml/L sulfuric acid solution (4.3) 500 ml, stir well, and store in a brown reagent bottle.

4.5 N-(1-Naphthyl)ethylenediamine hydrochloride stock solution, rho (C10H7NH(CH2)2NH2·2HCl)=1.00 g/L. Weigh 0.50 g N-(1-naphthalene Ethyldiamine hydrochloride in a 500 ml volumetric flask, diluted with water to dilute to the mark. This solution is stored in a closed brown bottle in the refrigerator Refrigerated for stable storage for three months.

4.6 Coloring solution. Weigh 5.0 g of p-aminobenzenesulfonic acid [NH2C6H4SO3H] and dissolve it in about.200 ml of hot water of 40-50 °C to cool the solution.

At room temperature, transfer all into a 1 000 ml volumetric flask and add 50 ml of N-(1-naphthyl)ethylenediamine hydrochloride stock solution (4.5) and 50 ml.

Glacial acetic acid, diluted to the mark with water. This solution is stored in a closed brown bottle and stored in the dark at 25 ° C for three months. If solution it is light red and should be discarded.

4.7 Absorbent. When using, mix the coloring solution (4.6) and water in a ratio of 4.1 (volume fraction), which is the absorption liquid. Absorbance of absorption liquid the degree should be less than or equal to 0.005.

4.8 nitrite standard stock solution, rho (NO2-)=250 µg/ml. accurately weigh 0.375 0 g sodium nitrite (NaNO2, excellent grade, use it is dissolved in water before drying at 105 °C ± 5 °C), transferred to a 1 000 ml volumetric flask, and diluted to the mark with water. This solution is stored in a sealed brown bottle Stored in the dark, it can be stored for three months.

4.9 Nitrite standard working solution, rho (NO2-)=2.5 µg/ml. Accurately absorb nitrite standard stock solution (4.8) 1.00 ml in 100 ml in a volumetric flask, dilute to the mark with water. Available now.

5 Instruments and equipment

5.1 Spectrophotometer.

5.2 Air sampler. The flow range is 0.1~1.0 L/min. When the sampling flow rate is 0.4 L/min, the relative error is less than ±5%.

5.3 Constant temperature, semi-automatic continuous air sampler. When the sampling flow rate is 0.2 L/min, the relative error is less than ±5%, and the temperature of the absorption liquid can be guaranteed.

Hold at 20 ° C ± 4 ° C. The sampling connection line is a borosilicate glass tube, a stainless steel tube, a Teflon tube or a silicone tube with an inner diameter of about 6 mm.

It may be shorter, no more than 2 m in any case, with a downward facing air inlet.

5.4 Absorbent bottle. A porous glass plate absorption bottle that can hold 10 ml, 25 ml or 50 ml of absorption liquid. The height of the liquid column is not less than 80 mm. Absorption bottle the resistance of the glass plate, the uniformity of bubble dispersion and the sampling efficiency are checked in accordance with Appendix A of this standard. Figure 1 shows two porous glass plates that are more suitable.

Absorb the bottle. Use a brown absorbing bottle or a black hood for the absorbing bottle cover during sampling. New porous glass plate absorption bottle or porous glass after use Plate absorption bottle, apply (1 1) HCl soak for more than 24 h, wash with water.

5.5 Oxidation bottle. A gas cylinder that can hold 5 ml, 10 ml or 50 ml acid potassium permanganate solution (4.4). The height of the liquid column should not be lower than 80 mm.

After use, the solution was washed with a hydroxylamine hydrochloride solution (4.2). Figure 2 shows two suitable oxidation bottles.

10 Ml 50 ml

50 Ml10 ml

Fig.1 Schematic diagram of the absorption bottle of the porous glass plateFig. 2 Schematic diagram of the oxidation bottle

6 interference and elimination when the mass concentration of sulfur dioxide in the air is 30 times the mass concentration of nitrogen oxides, it negatively interferes with the determination of nitrogen dioxide.

Peroxyacetyl octoate (PAN) in the air produces positive interference with the determination of nitrogen dioxide.

When the concentration of ozone in the air exceeds 0.25 mg/m3, it negatively interferes with the determination of nitrogen dioxide. At the inlet end of the sampling bottle when sampling Connect a length of 15 to 20 cm long silicone rubber tube to eliminate interference.

7 samples

7.1 Short time sampling (within 1 h) Take two porous glass plate absorption bottles containing 10.0 ml of absorbing liquid and one oxygen containing 5-10 ml of acidic potassium permanganate solution (4.4) to make the bottle (the height of the liquid column is not less than 80 mm), use the shortest silicone rubber tube to connect the oxidation bottle in series between the two absorption bottles (see Figure 3).

0.4 L/min flow rate 4~24 L.

7.2 Long time sampling (24 h) Take two large porous glass plate absorption bottles and fill in 25.0 ml or 50.0 ml absorption liquid (4.7) (the liquid column height is not less than 80 mm).

Record the liquid level position. Take an oxidized bottle containing 50 ml of acidic potassium permanganate solution (4.4) and access the sampling system as shown in Figure 4.

The liquid is kept at a constant temperature of 20 °C ± 4 °C, and 288 L is produced at a flow rate of 0.2 L/min.

Note. When there is obvious precipitation in the oxidation tube, it should be replaced in time.

In general, an oxidizing bottle containing 50 ml of acidic potassium permanganate solution can be used for 15 to 20 days (sampled every other day).

During the sampling process, observe the color change of the absorption liquid to avoid penetration due to excessive mass concentration of nitrogen oxides.

7.3 Sampling requirements the airtightness of the sampling system should be checked before sampling, and the flow calibration should be performed using a soap membrane flow meter. The relative error of the sample flow should be less than ± 5%.

Sunlight should be avoided during sample transport and storage during sampling. When the temperature exceeds 25 °C, transport for a long time (more than 8 h) and Cooling measures should be taken when storing samples.

At the end of sampling, to prevent the solution from sucking up, close the water stop clip or electricity connected to the sampling system while the sampling pump stops pumping.

Magnetic valve (see Figure 3 or Figure 4).

Absorption bottle

Oxidized bottle

Absorption bottle

Silica gel dry bottle flowmeter Gas pump Water stop clip

Figure 3 Schematic diagram of manual sampling series

Absorption bottle

Oxidized bottle

Absorption bottle

Silica gel dry bottle flowmeter Gas pump solenoid valve

Figure 4 Schematic diagram of continuous automatic sampling series

7.4 Field blank

The absorption bottle containing the absorption liquid is taken to the sampling site, stored under the same conditions as the sample, and transported until it is sent to the laboratory for analysis.

Care should be taken to prevent contamination during the transfer.

At least 2 field blank tests are required for each sample.

7.5 Storage of samples Samples are collected, transported, and stored in the dark, and stored as soon as possible after sample collection. If it cannot be measured in time, the sample will be dark at low temperature.

Store at room, the sample is stored in the dark at 30 °C, stable for 8 h; stored in the dark at 20 °C, stable for 24 h; refrigerated at 0 ~ 4 ° C, at least Stable for 3 days.

8 Analysis steps

8.1 Drawing of standard curves Take 6 10 ml plug colorimetric tubes and prepare a series of nitrite standard solutions according to Table 1. According to Table 1, separately transfer the corresponding volume of nitrous oxide Sodium standard working solution (4.9), add water to 2.00 ml, and add coloring solution (4.6) 8.00 ml.

Table 1 NO2- standard solution series

Pipe number 0 1 2 3 4 5 Standard working fluid (4.9)/ml 0.00 0.40 0.80 1.20 1.60 2.00 Water/ml 2.00 1.60 1.20 0.80 0.40 0.00 Coloring solution (4.6)/ml 8.00 8.00 8.00 8.00 8.00 8.00 NO2- mass concentration/(µg/ml) 0.00 0.10 0.20 0.30 0.40 0.50 Mix the tubes and place them in the dark for 20 min (room temperature is below 40 °C for more than 40 min), using a 10 mm cuvette at the wavelength at 540 nm, the absorbance is measured with water as the reference. After subtracting the absorbance of the No. 0 tube, the mass concentration (µg/ml) corresponding to NO2- is used.

The regression equation of the standard curve is calculated by the small square method.

The slope of the standard curve is controlled at 0.960 to 0.978 absorbance·ml/µg, and the intercept is controlled between 0.000 and 0.005 (painted in 5 ml volume) when the standard curve is prepared, the slope of the standard curve is controlled at 0.180 to 0.195 absorbance·ml/µg and the intercept is controlled to ±0.003).

8.2 Blank test

8.2.1 Laboratory blank test. Take unsampled blank absorbing solution in the laboratory, using a 10 mm cuvette at 540 nm.

The absorbance was measured using water as a reference. The laboratory blank absorbance A0 does not exceed ±15% under the conditions specified by the color development.

8.2.2 Field blank. Same as 8.2.1 Determination of absorbance. Compare the field blank with the measurement results of the laboratory blank, if the site is blank and real the gap between the chambers is too large, find the cause, and resample.

8.3 Sample determination After sampling for 20 min, leave it at room temperature below 20 °C for more than 40 min, and add the volume of the absorption liquid in the sample bottle to the mark with water.

Mix well. The absorbance of the blank sample was measured using a 10 mm cuvette at a wavelength of 540 nm with water as a reference.

If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with a laboratory blank test solution and measure the absorbance. But the dilution factor is not it is greater than 6.

9 results indicate

9.1 Mass concentration of nitrogen dioxide in air 2NO rho (mg/m3) is calculated according to formula (1).

( )AA a VD

Bf V

rho - - × ×= × × (1)

9.2 Mass concentration of nitric oxide in air NOrho (mg/m3) is calculated by the formula (2) based on nitrogen dioxide (NO2).

( )AA a VD

Bf VK

rho - - × ×= × × × (2) NOrho' (mg/m3) is calculated by formula (3) based on nitric oxide (NO).

rhorho ×' = (3)

9.3 The mass concentration of nitrogen oxides in the air NOxrho (mg/m3) is calculated by the formula (4) based on nitrogen dioxide (NO2).

2NO NO Nx O

rho rho rho= (4)

In the above formulas. A1, A2--the absorbance of the sample in the first and second absorption bottles in series;

A0--the absorbance of the laboratory blank;

B--the slope of the standard curve, absorbance · ml/µg;

A--the intercept of the standard curve;

V--the volume of the absorption liquid for sampling, ml;

V0--sampled to the standard state (101.325 kPa, 273 K), L;

K--NO->NO2 oxidation coefficient, 0.68;

D--the dilution factor of the sample;

f--Saltzman experimental coefficient, 0.88 (w when the mass concentration of nitrogen dioxide in the air is higher than 0.72 mg/m3, f is 0.77).

10 Precision and accuracy

10.1 Determination of the precision and accuracy of NO2 standard gas Five laboratories measured NO2 standard gas with a mass concentration ranging from 0.056 to 0.480 mg/m3, and the repeatability relative standard deviation was less than 10%, the relative error is less than ±8%.

10.2 Determination of the precision and accuracy of NO standard gases Determination of NO standard gas with a mass concentration ranging from 0.057 to 0.396 mg/m3, the relative standard deviation of repeatability is less than 10%, relative error the difference is less than ±10%.

Appendix A

(normative appendix) Absorption bottle inspection and sampling efficiency determination A.1 Glass plate resistance and micropore uniformity inspection the new perforated glass plate absorption bottle is immersed for 24 hours or more with HCl (1 1) before being inspected and washed with water.

Each absorbing bottle should be measured for its glassboard resistance before use or after a period of use, and the uniformity of bubble dispersion after passing through the glass plate should be checked.

Absorbent bottles that do not meet the requirements for resistance and have uneven bubble dispersion should n...