GB/T 15436-1995 Determination of nitrogen oxides in ambient air - Saltzman method
Some standard content:
National Standard of the People's Republic of China
Determination of nitrogen oxides in ambient air
Saltzman method
Ambient air-Determination of nitrogenoxideldeg-Saltzman method
1 Subject content and applicable scope
1.1 Subject content
This standard specifies the spectrophotometric method for determining nitrogen oxides in ambient air. This standard is divided into two parts:
Part I: Acidic potassium permanganate solution oxidation method Part II: Chromium trifluoride-quartz sand oxidation method 1.2 Scope of application
GB/T15436—1995
When the sampling volume is 424L, this standard is applicable to the determination of nitrogen oxides in the air in the concentration range of 0.015~2.0mg/mll. Part 1 Acidic potassium permanganate solution oxidation method 2 Terminology
2.1 Nitrogen oxides (in terms of NO,): refers to the oxides of ammonia in the form of hydrogen monoxide and nitrogen dioxide in the air. 2.2 Saltzman experimental coefficient () The ratio of the amount of azo dye equivalent to nitrite absorbed by the absorption liquid in the gas sampling process of the nitrogen dioxide calibration mixed gas prepared by the permeation method to the total amount of nitrogen dioxide passing through the sampling system. This coefficient is the average value of repeated experimental measurements. The determination method is shown in Appendix B. 2.3 Oxidation coefficient (K): After the nitric oxide in the air passes through the oxidation tube, it is oxidized to nitrogen dioxide and absorbed by the absorption liquid to generate azo dye, and the total amount of nitric oxide passing through the sampling system. 3 Principle
Nitrogen dioxide in the air is absorbed by the absorption liquid in the first absorption bottle in series to generate dihydrogen dye. Nitric oxide in the air does not react with the absorption liquid. After being oxidized to nitrogen dioxide through the oxidation tube, it is absorbed by the absorption liquid in the first absorption bottle in series to generate pink azo dye. The absorbance is measured at wavelengths between 540 and 545 nm. 4 Reagents
Unless otherwise specified, analytical reagents that meet national standards and distilled water without nitrite or water of equal purity are used during analysis. If necessary, a small amount of potassium permanganate and oxygen oxide lock can be added to the all-glass distiller for re-distillation. The test method for water purity is that the absorbance of the absorption liquid does not exceed 0.005 (540-545nm. 10mm colorimetric cup, water as reference). Approved by Guohao Environmental Protection Bureau on March 25, 1995 and implemented on August 1, 1995
GB/T154361995
4. 1 N-(1-naphthyl)ethylenediamine acid salt stock solution: β - 1. 00 g/L. Weigh 0.50 g of N-(1-naphthyl)ethylenediamine hydrochloride [CH,NH(CH,),NH. ·2HCl in a 500ml volumetric flask, dissolve and dilute to the mark with water, store this solution in a sealed brown bottle, and keep it stable for three months under refrigeration: 4.2 Color development solution: Weigh 5.0 g of p-nitrobenzenesulfonic acid ENIHC,HSOII and dissolve it in about 200 ml of hot water. Cool the solution to room temperature and transfer it all to a 100ml volumetric flask. Add 50.0 ml of N-(1-naphthyl)ethylenediamine hydrochloride stock solution (4.1) and 50 ml of glacial acetic acid, and dilute to the mark with water. Store this solution in a sealed brown bottle, and keep it in a dark place below 25°C for three tablets. If the solution is light red, it should be re-prepared.
4.3 Absorption solution: When ready to use, mix the color developing solution (4.2) and water in a ratio of 4+1 (V/V) to obtain the absorption solution. 4.4 Standard stock solution of nitrate: 250mgNU/L Accurately weigh 0.3750g sodium nitrite (NaNO)2. Superior purity, pre-place it in a desiccator for 241) and dissolve it in water, transfer it into a 1000tL volumetric flask, and dilute it to the mark with water. This solution is stored in a sealed brown bottle in a dark place and can be stable for one month:
4.5 Standard working solution of nitrite: 2.50mgV)/l. Pipette 1.00ml of standard stock solution of nitrate <4.4> into a 100ml volumetric flask, and dilute it to the mark with water. Prepare it before use. 4.6 Sulfuric acid solution: r (1/2HzS0) -1mol/L: Take 15mL concentrated acid (pzc-1.84g/ml.). Slowly add 500mL water. 4.7 Acidic potassium permanganate solution: Weigh 25 potassium permanganate, heat it slightly to dissolve it all in 500ml. Water, then add 1mol/sulphuric acid solution (4.6) 500mL to mix, put it in a brown reagent bottle, 4.B ammonium hydrochloride solution: 0-0.20.5g/L, 5 Instruments
5.1 Sampling probe: borophosphorus glass, stainless steel, polytetrafluoroethylene or silicone rubber tube. The inner diameter is about 6mm, as short as possible, no longer than 2m in any case: equipped with a downward air inlet. 5.2 Absorption bottle: A porous glass plate absorption bottle with 10.25 or 50 mL of absorption liquid, with a liquid column of not less than 80 mm. According to Appendix A of this standard, the glass plate resistance, uniformity of bubble dispersion and sampling efficiency of the absorption bottle are checked. Figure 1 shows two more suitable porous glass plate absorption bottles. 5.3 Oxidation bottle: A gas washing bottle with 5~10 mL and 50 mL of acidic potassium permanganate solution (4.7), with a liquid column of not less than 80 mm. After use, wash with hydroxylamine hydrochloride solution (1.8). Figure 2 shows two more suitable oxidation bottles. 5.4 Air sampler:
5.4.1 Portable air sampler: Flow range 0~1L./min. When the sampling volume is 0.1L/min, the error is less than 5%. 5.4.2 Constant temperature, automatic reverse sampler: When the sampling flow rate is 0.21./min, the error is less than 5%, and the absorption liquid temperature can be kept at 20+4T5.5 Spectrophotometer,
6 Sample
6.1 Short-time sampling (within 1h) Take two porous glass plate absorption bottles containing 10.9mL absorption liquid and one containing 5~10mL acid The oxidation bottle of potassium permanganate solution (4.7) (the liquid column is not less than 80mm), use the shortest possible silicone tube to connect the oxidation bottle in series between the two absorption bottles (see Figure 3a), and collect gas at a flow rate of 0.1L./min for 4 to 241.6.2 Long-term sampling (24h): Take two human-shaped porous glass plate absorption bottles, fill them with 25.0ml. or 50,0mL absorption wave (4.3), the liquid column is not less than 80{m). Mark the moving surface position. Take another oxidation bottle containing 50mT. acidic potassium permanganate liquid (4.7), and connect it to the sampling system as shown in Figure 3l. Warm the absorption liquid to 20.4C. At 9:00 to the secondary port at 9:00, collect gas at a flow rate of 0.21./min for 288T.ItmL
GB/T 15436--1995
Figure 1 Schematic diagram of porous glass plate absorption bottle
Good image gel
Acyl image gel
The best collection
Absorption spot
Absorption bottle
Lower drying bottle
Figure 2 Schematic diagram of oxidation bottle
Water stop
Figure 3a Schematic diagram of NO, NO and N), manual sampling series oxidation head
Both interference
Drying bottle
Solenoid valve
Current limiting valve
Figure 3h Schematic diagram of NO), NO, NO, continuous white dynamic sampling series When there is obvious precipitation in the crown bottle, it should be replaced in time. Note: Generally, an oxidation bottle containing 50 mL of a relatively high-quality potassium peroxide solution can be used for 15 to 20 days (sampling every other day). During sampling, samples should be protected from sunlight during transportation and storage. When the temperature exceeds 25°C, cooling measures should be taken for long-term transportation and storage (more than 8 hours). At the end of sampling, in order to prevent liquid from being sucked in, the sampling pump should stop pumping and close the water stop clamp or solenoid valve (Figure 3al or 3b) connected to the sampling system. 6. 3 Interference and elimination When the oxygen concentration in the air exceeds 0.250 mg/m3, negative interference will be generated in the determination of nitric oxide. When sampling, connect a 75~20cm long silicone hose to the inlet of the absorption bottle to eliminate interference. 7 Analysis steps
7.1 Drawing of standard curve
GB/T 15436—1995
Take 6 10mL stoppered colorimetric tubes to prepare nitrite standard solution chromatogram according to the following table: NO2 standard solution chromatogram
Standard working solution (4.5).mE.
Color developing solution (4.2).mL
NO2 concentration, g/mL
Mix each tube and place it in a dark place for 20 min (more than 10 min when the room temperature is below 20℃), use 10 mrm colorimetric tube III, at a wavelength between 540~545 μm, measure the absorbance with water as reference, after deducting the absorbance of the blank test, the corresponding NO2 concentration (μgmL), use the least squares method to calculate the regression equation of the standard curve. 7.2 Sample determination
Put aside for 20 min after sampling, put it under the cover at room temperature below 20℃ for more than 40 min, add water to the volume absorbed in the sampling bottle to the mark, and mix well. Measure the absorbance of the sample and the blank test sample according to 7.1. If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with the blank test solution and then measure its absorbance. The absorbance of the sample should be measured as soon as possible after sampling. If it cannot be measured in time, the sample should be stored in a low temperature and dark place. The sample can be stable for 8h when stored in a dark place at 30℃. It can be stable for 24h when stored in a dark place at 20℃. It can be stable for at least three days when refrigerated in a refrigerator. 8 Result expression
8. 1 Calculation of nitrogen dioxide concentration in the air: = (A, - A -a) XV×D
8. 2 Nitrogen monohydride concentration in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry it at 105℃. Stir it several times during the drying process. The finished blue chromium oxide-quartz sand should be loose. If it sticks together, it means that the proportion of chromium monoxide is too large. You can add some quartz sand to prepare it again. || tt||Put the chromium trioxide-quartz sand into a double-ball glass tube (Figure 4), plug both ends with a small amount of absorbent cotton, and seal both ends with a small cap made of latex tube plugged with glass beads. When in use, a short piece of silicone rubber tube is used to connect the oxidation tube and the absorption bottle. LoU
Figure 4 Double-ball glass tube
12 Sample
Take a porous glass plate absorption bottle, fill it with 10mL absorption liquid (4.3), mark the liquid level, and use a short piece of silicone rubber tube to connect the oxidation tube (Chapter 11) to the inlet end of the absorption bottle (the tube mouth is slightly tilted downward), and collect 4 to 24L of gas at a flow rate of 0.4ml./min. Avoid sunlight during sampling, transportation and storage of samples. The chromium trioxide-quartz sand oxidation tube is suitable for use when the relative air humidity is 30% to 70%. The oxidation tube should be replaced when the relative air humidity is higher than normal (close to 70%). The oxidation tube should be replaced in time if it becomes hardened or partially turns green due to moisture absorption. 13 Analysis steps
Same as Chapter 7.
14 Result expression
GB/T 15436--1995
The concentration of nitrogen oxides in the air is calculated as follows: Cvo
Wherein: Cnn,
(AA, -) ×VXD)
6
The concentration of nitrogen oxides in the air (in terms of N0:) mg/m; AA
is the absorbance of the sample and the air test sample respectively; b, a-
is the slope of the standard curve (absorbance·m/) and intercept respectively: The volume of the absorption liquid used for sampling, ml.
Converted to standard state (101.3kP, 273 K) sampling volume, I-; L) - dilution factor of the sample;
Seitzman experimental coefficient, 0.88 (air coin tNO, when the concentration exceeds 0.720 mg/m*, the factory value is 0.77) 15 Precision and accuracy
Repeatedly measure the NO standard gas with a concentration range of 0.057~~0.396 mg/m*, the coefficient of variation is less than 10%, and the relative error is less than three 10.
A1 Glass plate resistance and micropore uniformity inspection
CB/T 154361995
Appendix A
Inspection rate of absorption bottle
(Supplement
Before use, the new porous glass plate absorption bottle should be soaked in (1+1) HCl for 24 The above, wash with clean water, each absorption bottle should be measured before use or after a period of use, the plate resistance should be checked to check the uniformity of bubble dispersion after passing through the glass plate. The absorption bottle with resistance that does not meet the requirements and uneven bubble dispersion should not be used.
For a porous glass plate absorption bottle containing 10inL absorption liquid, when sampling at a flow rate of 0.41./min, the glass resistance is 4~-5kPa: The bubbles after passing through the glass should be evenly dispersed:
For a large porous glass plate absorption bottle containing 5Uml. absorption liquid, when sampling at a flow rate of 0.2L/min, the glass resistance is 5~6kP. The bubbles after passing through the glass are evenly dispersed:
A2 Determination of sampling efficiency
Before use of the absorption bottle And after using it for a period of time, its sampling efficiency should be measured. Connect two absorption bottles in series, operate according to Article 6.1, collect ambient air, and stop sampling when the NO concentration in the first absorption bottle is about 0.4/ml. Measure the absorbance of the samples in the front and back absorption bottles according to Article 7.1, and calculate the sampling efficiency (E) of the first absorption bottle according to formula (A1): C
are the concentrations of NO in the first and second absorption bottles in series, ug/mL respectively. In the formula: Gz
Note: Absorption bottles with a sampling efficiency E lower than . are not suitable for use. Appendix B
Determination of Salzman experimental coefficient
(Supplement)
. (A1?
According to GB Prepare zero gas and mixed gas for chlorine dioxide calibration in the concentration range to be measured by the method specified in 5275. Collect gas samples according to the operation of Section 6.1. When the N(.) content in the absorption liquid reaches about 0.4 fu/㎡I, stop sampling. Measure the absorbance of the sample according to Section 7.1 and calculate the Saltztnan experimental coefficient (f) according to the formula (Bli): 4-4-a) × V
b XV x Cso.
Where: A——absorbance of sample solution; A.--absorbance of blank test (zero concentration) sample; α--slope (absorbance·ml/g) and intercept of the standard curve measured according to Section 7.|; V-volume of absorption liquid for sampling.ml
V-volume of deep sample converted to standard state (101.3 kPa, 273 K).L;C. -Concentration of NO. standard mixed gas passing through the sampling system.mg/m (101.3kPa.273K)tB1
GB/T15436-1995
The f value is affected by factors such as NO. concentration in the air, sampling flow, absorption bottle type, sampling efficiency, etc. Therefore, when measuring the f value, the measurement conditions should be kept consistent with the actual sampling conditions. Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the Zhenyang City Environmental Monitoring Center Station. The main drafters of this standard are Wang Yuping, Chen Tao, Wang Juan, Li Jing, and Cao Kun.Use water to fill the volume absorbed in the sampling bottle to the mark and mix well. Measure the absorbance of the sample and the blank test sample according to 7.1. If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with the blank test solution and then measure its absorbance. The absorbance of the sample should be measured as soon as possible after sampling. If it cannot be measured in time, the sample should be stored in a low temperature dark place. The sample can be stable for 8h when stored in a dark place at 30℃. It can be stable for 24h when stored in a dark place at 20℃. It can be stable for at least three days when refrigerated in a refrigerator. 8 Result expression
8. 1 Calculation of nitrogen dioxide concentration in the air: = (A, - A -a) XV×D
8. 2 Nitrogen monohydride concentration in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry it at 105℃. Stir it several times during the drying process. The finished blue chromium oxide-quartz sand should be loose. If it sticks together, it means that the proportion of chromium monoxide is too large. You can add some quartz sand to prepare it again. || tt||Put the chromium trioxide-quartz sand into a double-ball glass tube (Figure 4), plug both ends with a small amount of absorbent cotton, and seal both ends with a small cap made of latex tube plugged with glass beads. When in use, a short piece of silicone rubber tube is used to connect the oxidation tube and the absorption bottle. LoU
Figure 4 Double-ball glass tube
12 Sample
Take a porous glass plate absorption bottle, fill it with 10mL absorption liquid (4.3), mark the liquid level, and use a short piece of silicone rubber tube to connect the oxidation tube (Chapter 11) to the inlet end of the absorption bottle (the tube mouth is slightly tilted downward), and collect 4 to 24L of gas at a flow rate of 0.4ml./min. Avoid sunlight during sampling, transportation and storage of samples. The chromium trioxide-quartz sand oxidation tube is suitable for use when the relative air humidity is 30% to 70%. The oxidation tube should be replaced when the relative air humidity is higher than normal (close to 70%). The oxidation tube should be replaced in time if it becomes hardened or partially turns green due to moisture absorption. 13 Analysis steps
Same as Chapter 7.
14 Result expression
GB/T 15436--1995
The concentration of nitrogen oxides in the air is calculated as follows: Cvo
Wherein: Cnn,
(AA, -) ×VXD)
6
The concentration of nitrogen oxides in the air (in terms of N0:) mg/m; AA
is the absorbance of the sample and the air test sample respectively; b, a-
is the slope of the standard curve (absorbance·m/) and intercept respectively: The volume of the absorption liquid used for sampling, ml.
Converted to standard state (101.3kP, 273 K) sampling volume, I-; L) - dilution factor of the sample;
Seitzman experimental coefficient, 0.88 (air coin tNO, when the concentration exceeds 0.720 mg/m*, the factory value is 0.77) 15 Precision and accuracy
Repeatedly measure the NO standard gas with a concentration range of 0.057~~0.396 mg/m*, the coefficient of variation is less than 10%, and the relative error is less than three 10.
A1 Glass plate resistance and micropore uniformity inspection
CB/T 154361995
Appendix A
Inspection rate of absorption bottle
(Supplement
Before use, the new porous glass plate absorption bottle should be soaked in (1+1) HCl for 24 The above, wash with clean water, each absorption bottle should be measured before use or after a period of use, the plate resistance should be checked to check the uniformity of bubble dispersion after passing through the glass plate. The absorption bottle with resistance that does not meet the requirements and uneven bubble dispersion should not be used.
For a porous glass plate absorption bottle containing 10inL absorption liquid, when sampling at a flow rate of 0.41./min, the glass resistance is 4~-5kPa: The bubbles after passing through the glass should be evenly dispersed:
For a large porous glass plate absorption bottle containing 5Uml. absorption liquid, when sampling at a flow rate of 0.2L/min, the glass resistance is 5~6kP. The bubbles after passing through the glass are evenly dispersed:
A2 Determination of sampling efficiency
Before use of the absorption bottle And after using it for a period of time, its sampling efficiency should be measured. Connect two absorption bottles in series and operate according to Article 6.1 to collect ambient air. When the NO concentration in the first absorption bottle is about 0.4/ml, stop sampling. Measure the absorbance of the samples in the front and back absorption bottles according to Article 7.1, and calculate the sampling efficiency (E) of the first absorption bottle according to formula (A1): C
are the concentrations of NO in the first and second absorption bottles in series, ug/mL respectively. In the formula: Gz
Note: Absorption bottles with a sampling efficiency E lower than . are not suitable for use. Appendix B
Determination of Salzman experimental coefficient
(Supplement)
. (A1?
According to GB Prepare zero gas and mixed gas for chlorine dioxide calibration in the concentration range to be measured by the method specified in 5275. Collect gas samples according to the operation of Section 6.1. When the N(.) content in the absorption liquid reaches about 0.4 fu/㎡I, stop sampling. Measure the absorbance of the sample according to Section 7.1 and calculate the Saltztnan experimental coefficient (f) according to the formula (Bli): 4-4-a) × V
b XV x Cso.
Where: A——absorbance of sample solution; A.--absorbance of blank test (zero concentration) sample; α--slope (absorbance·ml/g) and intercept of the standard curve measured according to Section 7.|; V-volume of absorption liquid for sampling.ml
V-volume of deep sample converted to standard state (101.3 kPa, 273 K).L;C. -Concentration of NO. standard mixed gas passing through the sampling system.mg/m (101.3kPa.273K)tB1
GB/T15436-1995
The f value is affected by factors such as NO. concentration in the air, sampling flow, absorption bottle type, sampling efficiency, etc. Therefore, when measuring the f value, the measurement conditions should be kept consistent with the actual sampling conditions. Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the Zhenyang City Environmental Monitoring Center Station. The main drafters of this standard are Wang Yuping, Chen Tao, Wang Juan, Li Jing, and Cao Kun.Use water to fill the volume absorbed in the sampling bottle to the mark and mix well. Measure the absorbance of the sample and the blank test sample according to 7.1. If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with the blank test solution and then measure its absorbance. The absorbance of the sample should be measured as soon as possible after sampling. If it cannot be measured in time, the sample should be stored in a low temperature dark place. The sample can be stable for 8h when stored in a dark place at 30℃. It can be stable for 24h when stored in a dark place at 20℃. It can be stable for at least three days when refrigerated in a refrigerator. 8 Result expression
8. 1 Calculation of nitrogen dioxide concentration in the air: = (A, - A -a) XV×D
8. 2 Nitrogen monohydride concentration in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry it at 105℃. Stir it several times during the drying process. The finished blue chromium oxide-quartz sand should be loose. If it sticks together, it means that the proportion of chromium monoxide is too large. You can add some quartz sand to prepare it again. || tt||Put the chromium trioxide-quartz sand into a double-ball glass tube (Figure 4), plug both ends with a small amount of absorbent cotton, and seal both ends with a small cap made of latex tube plugged with glass beads. When in use, a short piece of silicone rubber tube is used to connect the oxidation tube and the absorption bottle. LoU
Figure 4 Double-ball glass tube
12 Sample
Take a porous glass plate absorption bottle, fill it with 10mL absorption liquid (4.3), mark the liquid level, and use a short piece of silicone rubber tube to connect the oxidation tube (Chapter 11) to the inlet end of the absorption bottle (the tube mouth is slightly tilted downward), and collect 4 to 24L of gas at a flow rate of 0.4ml./min. Avoid sunlight during sampling, transportation and storage of samples. The chromium trioxide-quartz sand oxidation tube is suitable for use when the relative air humidity is 30% to 70%. The oxidation tube should be replaced when the relative air humidity is higher than normal (close to 70%). The oxidation tube should be replaced in time if it becomes hardened or partially turns green due to moisture absorption. 13 Analysis steps
Same as Chapter 7.
14 Result expression
GB/T 15436--1995
The concentration of nitrogen oxides in the air is calculated as follows: Cvo
Wherein: Cnn,
(AA, -) ×VXD)
6
The concentration of nitrogen oxides in the air (in terms of N0:) mg/m; AA
is the absorbance of the sample and the air test sample respectively; b, a-
is the slope of the standard curve (absorbance·m/) and intercept respectively: The volume of the absorption liquid used for sampling, ml.
Converted to standard state (101.3kP, 273 K) sampling volume, I-; L) - dilution factor of the sample;
Seitzman experimental coefficient, 0.88 (air coin tNO, when the concentration exceeds 0.720 mg/m*, the factory value is 0.77) 15 Precision and accuracy
Repeatedly measure the NO standard gas with a concentration range of 0.057~~0.396 mg/m*, the coefficient of variation is less than 10%, and the relative error is less than three 10.
A1 Glass plate resistance and micropore uniformity inspection
CB/T 154361995
Appendix A
Inspection rate of absorption bottle
(Supplement
Before use, the new porous glass plate absorption bottle should be soaked in (1+1) HCl for 24 The above, wash with clean water, each absorption bottle should be measured before use or after a period of use, the plate resistance should be checked to check the uniformity of bubble dispersion after passing through the glass plate. The absorption bottle with resistance that does not meet the requirements and uneven bubble dispersion should not be used.
For a porous glass plate absorption bottle containing 10inL absorption liquid, when sampling at a flow rate of 0.41./min, the glass resistance is 4~-5kPa: The bubbles after passing through the glass should be evenly dispersed:
For a large porous glass plate absorption bottle containing 5Uml. absorption liquid, when sampling at a flow rate of 0.2L/min, the glass resistance is 5~6kP. The bubbles after passing through the glass are evenly dispersed:
A2 Determination of sampling efficiency
Before use of the absorption bottle And after using it for a period of time, its sampling efficiency should be measured. Connect two absorption bottles in series and operate according to Article 6.1 to collect ambient air. When the NO concentration in the first absorption bottle is about 0.4/ml, stop sampling. Measure the absorbance of the samples in the front and back absorption bottles according to Article 7.1, and calculate the sampling efficiency (E) of the first absorption bottle according to formula (A1): C
are the concentrations of NO in the first and second absorption bottles in series, ug/mL respectively. In the formula: Gz
Note: Absorption bottles with a sampling efficiency E lower than . are not suitable for use. Appendix B
Determination of Salzman experimental coefficient
(Supplement)
. (A1?
According to GB Prepare zero gas and mixed gas for chlorine dioxide calibration in the concentration range to be measured by the method specified in 5275. Collect gas samples according to the operation of Section 6.1. When the N(.) content in the absorption liquid reaches about 0.4 fu/㎡I, stop sampling. Measure the absorbance of the sample according to Section 7.1 and calculate the Saltztnan experimental coefficient (f) according to the formula (Bli): 4-4-a) × V
b XV x Cso.
Where: A——absorbance of sample solution; A.--absorbance of blank test (zero concentration) sample; α--slope (absorbance·ml/g) and intercept of the standard curve measured according to Section 7.|; V-volume of absorption liquid for sampling.ml
V-volume of deep sample converted to standard state (101.3 kPa, 273 K).L;C. -Concentration of NO. standard mixed gas passing through the sampling system.mg/m (101.3kPa.273K)tB1
GB/T15436-1995
The f value is affected by factors such as NO. concentration in the air, sampling flow, absorption bottle type, sampling efficiency, etc. Therefore, when measuring the f value, the measurement conditions should be kept consistent with the actual sampling conditions. Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the Zhenyang City Environmental Monitoring Center Station. The main drafters of this standard are Wang Yuping, Chen Tao, Wang Juan, Li Jing, and Cao Kun.1. Measure the absorbance of the sample and the blank test sample. If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with the blank test solution and then measure its absorbance. The absorbance of the sample should be measured as soon as possible after sampling. If it cannot be measured in time, the sample should be stored in a low temperature dark place. The sample can be stable for 8h when stored in a dark place at 30℃. It can be stable for 24h when stored in a dark place at 20℃. It can be stable for at least three days when refrigerated in a refrigerator. 8. Result expression
8. 1 Calculation of nitrogen dioxide concentration in the air: = (A, - A -a) XV×D
8. 2 Nitrogen monohydride concentration in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry it at 105℃. Stir it several times during the drying process. The finished blue chromium oxide-quartz sand should be loose. If it sticks together, it means that the proportion of chromium monoxide is too large. You can add some quartz sand to prepare it again. || tt||Put the chromium trioxide-quartz sand into a double-ball glass tube (Figure 4), plug both ends with a small amount of absorbent cotton, and seal both ends with a small cap made of latex tube plugged with glass beads. When in use, a short piece of silicone rubber tube is used to connect the oxidation tube and the absorption bottle. LoU
Figure 4 Double-ball glass tube
12 Sample
Take a porous glass plate absorption bottle, fill it with 10mL absorption liquid (4.3), mark the liquid level, and use a short piece of silicone rubber tube to connect the oxidation tube (Chapter 11) to the inlet end of the absorption bottle (the tube mouth is slightly tilted downward), and collect 4 to 24L of gas at a flow rate of 0.4ml./min. Avoid sunlight during sampling, transportation and storage of samples. The chromium trioxide-quartz sand oxidation tube is suitable for use when the relative air humidity is 30% to 70%. The oxidation tube should be replaced when the relative air humidity is higher than normal (close to 70%). The oxidation tube should be replaced in time if it becomes hardened or partially turns green due to moisture absorption. 13 Analysis steps
Same as Chapter 7.
14 Result expression
GB/T 15436--1995
The concentration of nitrogen oxides in the air is calculated as follows: Cvo
Wherein: Cnn,
(AA, -) ×VXD)
6
The concentration of nitrogen oxides in the air (in terms of N0:) mg/m; AA
is the absorbance of the sample and the air test sample respectively; b, a-
is the slope of the standard curve (absorbance·m/) and intercept respectively: The volume of the absorption liquid used for sampling, ml.
Converted to standard state (101.3kP, 273 K) sampling volume, I-; L) - dilution factor of the sample;
Seitzman experimental coefficient, 0.88 (air coin tNO, when the concentration exceeds 0.720 mg/m*, the factory value is 0.77) 15 Precision and accuracy
Repeatedly measure the NO standard gas with a concentration range of 0.057~~0.396 mg/m*, the coefficient of variation is less than 10%, and the relative error is less than three 10.
A1 Glass plate resistance and micropore uniformity inspection
CB/T 154361995
Appendix A
Inspection rate of absorption bottle
(Supplement
Before use, the new porous glass plate absorption bottle should be soaked in (1+1) HCl for 24 The above, wash with clean water, each absorption bottle should be measured before use or after a period of use, the plate resistance should be checked to check the uniformity of bubble dispersion after passing through the glass plate. The absorption bottle with resistance that does not meet the requirements and uneven bubble dispersion should not be used.
For a porous glass plate absorption bottle containing 10inL absorption liquid, when sampling at a flow rate of 0.41./min, the glass resistance is 4~-5kPa: The bubbles after passing through the glass should be evenly dispersed:
For a large porous glass plate absorption bottle containing 5Uml. absorption liquid, when sampling at a flow rate of 0.2L/min, the glass resistance is 5~6kP. The bubbles after passing through the glass are evenly dispersed:
A2 Determination of sampling efficiencywww.bzxz.net
Before use of the absorption bottle And after using it for a period of time, its sampling efficiency should be measured. Connect two absorption bottles in series and operate according to Article 6.1 to collect ambient air. When the NO concentration in the first absorption bottle is about 0.4/ml, stop sampling. Measure the absorbance of the samples in the front and back absorption bottles according to Article 7.1, and calculate the sampling efficiency (E) of the first absorption bottle according to formula (A1): C
are the concentrations of NO in the first and second absorption bottles in series, ug/mL respectively. In the formula: Gz
Note: Absorption bottles with a sampling efficiency E lower than . are not suitable for use. Appendix B
Determination of Salzman experimental coefficient
(Supplement)
. (A1?
According to GB Prepare zero gas and mixed gas for chlorine dioxide calibration in the concentration range to be measured by the method specified in 5275. Collect gas samples according to the operation of Section 6.1. When the N(.) content in the absorption liquid reaches about 0.4 fu/㎡I, stop sampling. Measure the absorbance of the sample according to Section 7.1 and calculate the Saltztnan experimental coefficient (f) according to the formula (Bli): 4-4-a) × V
b XV x Cso.
Where: A——absorbance of sample solution; A.--absorbance of blank test (zero concentration) sample; α--slope (absorbance·ml/g) and intercept of the standard curve measured according to Section 7.|; V-volume of absorption liquid for sampling.ml
V-volume of deep sample converted to standard state (101.3 kPa, 273 K).L;C. -Concentration of NO. standard mixed gas passing through the sampling system.mg/m (101.3kPa.273K)tB1
GB/T15436-1995
The f value is affected by factors such as NO. concentration in the air, sampling flow, absorption bottle type, sampling efficiency, etc. Therefore, when measuring the f value, the measurement conditions should be kept consistent with the actual sampling conditions. Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the Zhenyang City Environmental Monitoring Center Station. The main drafters of this standard are Wang Yuping, Chen Tao, Wang Juan, Li Jing, and Cao Kun.1. Measure the absorbance of the sample and the blank test sample. If the absorbance of the sample exceeds the upper limit of the standard curve, dilute it with the blank test solution and then measure its absorbance. The absorbance of the sample should be measured as soon as possible after sampling. If it cannot be measured in time, the sample should be stored in a low temperature dark place. The sample can be stable for 8h when stored in a dark place at 30℃. It can be stable for 24h when stored in a dark place at 20℃. It can be stable for at least three days when refrigerated in a refrigerator. 8. Result expression
8. 1 Calculation of nitrogen dioxide concentration in the air: = (A, - A -a) XV×D
8. 2 Nitrogen monohydride concentration in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry it at 105℃. Stir it several times during the drying process. The finished blue chromium oxide-quartz sand should be loose. If it sticks together, it means that the proportion of chromium monoxide is too large. You can add some quartz sand to prepare it again. || tt||Put the chromium trioxide-quartz sand into a double-ball glass tube (Figure 4), plug both ends with a small amount of absorbent cotton, and seal both ends with a small cap made of latex tube plugged with glass beads. When in use, a short piece of silicone rubber tube is used to connect the oxidation tube and the absorption bottle. LoU
Figure 4 Double-ball glass tube
12 Sample
Take a porous glass plate absorption bottle, fill it with 10mL absorption liquid (4.3), mark the liquid level, and use a short piece of silicone rubber tube to connect the oxidation tube (Chapter 11) to the inlet end of the absorption bottle (the tube mouth is slightly tilted downward), and collect 4 to 24L of gas at a flow rate of 0.4ml./min. Avoid sunlight during sampling, transportation and storage of samples. The chromium trioxide-quartz sand oxidation tube is suitable for use when the relative air humidity is 30% to 70%. The oxidation tube should be replaced when the relative air humidity is higher than normal (close to 70%). The oxidation tube should be replaced in time if it becomes hardened or partially turns green due to moisture absorption. 13 Analysis steps
Same as Chapter 7.
14 Result expression
GB/T 15436--1995
The concentration of nitrogen oxides in the air is calculated as follows: Cvo
Wherein: Cnn,
(AA, -) ×VXD)
6
The concentration of nitrogen oxides in the air (in terms of N0:) mg/m; AA
is the absorbance of the sample and the air test sample respectively; b, a-
is the slope of the standard curve (absorbance·m/) and intercept respectively: The volume of the absorption liquid used for sampling, ml.
Converted to standard state (101.3kP, 273 K) sampling volume, I-; L) - dilution factor of the sample;
Seitzman experimental coefficient, 0.88 (air coin tNO, when the concentration exceeds 0.720 mg/m*, the factory value is 0.77) 15 Precision and accuracy
Repeatedly measure the NO standard gas with a concentration range of 0.057~~0.396 mg/m*, the coefficient of variation is less than 10%, and the relative error is less than three 10.
A1 Glass plate resistance and micropore uniformity inspection
CB/T 154361995
Appendix A
Inspection rate of absorption bottle
(Supplement
Before use, the new porous glass plate absorption bottle should be soaked in (1+1) HCl for 24 The above, wash with clean water, each absorption bottle should be measured before use or after a period of use, the plate resistance should be checked to check the uniformity of bubble dispersion after passing through the glass plate. The absorption bottle with resistance that does not meet the requirements and uneven bubble dispersion should not be used.
For a porous glass plate absorption bottle containing 10inL absorption liquid, when sampling at a flow rate of 0.41./min, the glass resistance is 4~-5kPa: The bubbles after passing through the glass should be evenly dispersed:
For a large porous glass plate absorption bottle containing 5Uml. absorption liquid, when sampling at a flow rate of 0.2L/min, the glass resistance is 5~6kP. The bubbles after passing through the glass are evenly dispersed:
A2 Determination of sampling efficiency
Before use of the absorption bottle And after using it for a period of time, its sampling efficiency should be measured. Connect two absorption bottles in series and operate according to Article 6.1 to collect ambient air. When the NO concentration in the first absorption bottle is about 0.4/ml, stop sampling. Measure the absorbance of the samples in the front and back absorption bottles according to Article 7.1, and calculate the sampling efficiency (E) of the first absorption bottle according to formula (A1): C
are the concentrations of NO in the first and second absorption bottles in series, ug/mL respectively. In the formula: Gz
Note: Absorption bottles with a sampling efficiency E lower than . are not suitable for use. Appendix B
Determination of Salzman experimental coefficient
(Supplement)
. (A1?
According to GB Prepare zero gas and mixed gas for chlorine dioxide calibration in the concentration range to be measured by the method specified in 5275. Collect gas samples according to the operation of Section 6.1. When the N(.) content in the absorption liquid reaches about 0.4 fu/㎡I, stop sampling. Measure the absorbance of the sample according to Section 7.1 and calculate the Saltztnan experimental coefficient (f) according to the formula (Bli): 4-4-a) × V
b XV x Cso.
Where: A——absorbance of sample solution; A.--absorbance of blank test (zero concentration) sample; α--slope (absorbance·ml/g) and intercept of the standard curve measured according to Section 7.|; V-volume of absorption liquid for sampling.ml
V-volume of deep sample converted to standard state (101.3 kPa, 273 K).L;C. -Concentration of NO. standard mixed gas passing through the sampling system.mg/m (101.3kPa.273K)tB1
GB/T15436-1995
The f value is affected by factors such as NO. concentration in the air, sampling flow, absorption bottle type, sampling efficiency, etc. Therefore, when measuring the f value, the measurement conditions should be kept consistent with the actual sampling conditions. Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the Zhenyang City Environmental Monitoring Center Station. The main drafters of this standard are Wang Yuping, Chen Tao, Wang Juan, Li Jing, and Cao Kun.- A -a) XV×D
8. 2 Concentration of nitrogen monohydride in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry it at 105℃. Stir it several times during the drying process. The finished blue chromium oxide-quartz sand should be loose. If it sticks together, it means that the proportion of chromium monoxide is too large. You can add some quartz sand to prepare it again. || tt||Put the chromium trioxide-quartz sand into a double-ball glass tube (Figure 4), plug both ends with a small amount of absorbent cotton, and seal both ends with a small cap made of latex tube plugged with glass beads. When in use, a short piece of silicone rubber tube is used to connect the oxidation tube and the absorption bottle. LoU
Figure 4 Double-ball glass tube
12 Sample
Take a porous glass plate absorption bottle, fill it with 10mL absorption liquid (4.3), mark the liquid level, and use a short piece of silicone rubber tube to connect the oxidation tube (Chapter 11) to the inlet end of the absorption bottle (the tube mouth is slightly tilted downward), and collect 4 to 24L of gas at a flow rate of 0.4ml./min. Avoid sunlight during sampling, transportation and storage of samples. The chromium trioxide-quartz sand oxidation tube is suitable for use when the relative air humidity is 30% to 70%. The oxidation tube should be replaced when the relative air humidity is higher than normal (close to 70%). The oxidation tube should be replaced in time if it becomes hardened or partially turns green due to moisture absorption. 13 Analysis steps
Same as Chapter 7.
14 Result expression
GB/T 15436--1995
The concentration of nitrogen oxides in the air is calculated as follows: Cvo
Wherein: Cnn,
(AA, -) ×VXD)
6
The concentration of nitrogen oxides in the air (in terms of N0:) mg/m; AA
is the absorbance of the sample and the air test sample respectively; b, a-
is the slope of the standard curve (absorbance·m/) and intercept respectively: The volume of the absorption liquid used for sampling, ml.
Converted to standard state (101.3kP, 273 K) sampling volume, I-; L) - dilution factor of the sample;
Seitzman experimental coefficient, 0.88 (air coin tNO, when the concentration exceeds 0.720 mg/m*, the factory value is 0.77) 15 Precision and accuracy
Repeatedly measure the NO standard gas with a concentration range of 0.057~~0.396 mg/m*, the coefficient of variation is less than 10%, and the relative error is less than three 10.
A1 Glass plate resistance and micropore uniformity inspection
CB/T 154361995
Appendix A
Inspection rate of absorption bottle
(Supplement
Before use, the new porous glass plate absorption bottle should be soaked in (1+1) HCl for 24 The above, wash with clean water, each absorption bottle should be measured before use or after a period of use, the plate resistance should be checked to check the uniformity of bubble dispersion after passing through the glass plate. The absorption bottle with resistance that does not meet the requirements and uneven bubble dispersion should not be used.
For a porous glass plate absorption bottle containing 10inL absorption liquid, when sampling at a flow rate of 0.41./min, the glass resistance is 4~-5kPa: The bubbles after passing through the glass should be evenly dispersed:
For a large porous glass plate absorption bottle containing 5Uml. absorption liquid, when sampling at a flow rate of 0.2L/min, the glass resistance is 5~6kP. The bubbles after passing through the glass are evenly dispersed:
A2 Determination of sampling efficiency
Before use of the absorption bottle And after using it for a period of time, its sampling efficiency should be measured. Connect two absorption bottles in series and operate according to Article 6.1 to collect ambient air. When the NO concentration in the first absorption bottle is about 0.4/ml, stop sampling. Measure the absorbance of the samples in the front and back absorption bottles according to Article 7.1, and calculate the sampling efficiency (E) of the first absorption bottle according to formula (A1): C
are the concentrations of NO in the first and second absorption bottles in series, ug/mL respectively. In the formula: Gz
Note: Absorption bottles with a sampling efficiency E lower than . are not suitable for use. Appendix B
Determination of Salzman experimental coefficient
(Supplement)
. (A1?
According to GB Prepare zero gas and mixed gas for chlorine dioxide calibration in the concentration range to be measured by the method specified in 5275. Collect gas samples according to the operation of Section 6.1. When the N(.) content in the absorption liquid reaches about 0.4 fu/㎡I, stop sampling. Measure the absorbance of the sample according to Section 7.1 and calculate the Saltztnan experimental coefficient (f) according to the formula (Bli): 4-4-a) × V
b XV x Cso.
Where: A——absorbance of sample solution; A.--absorbance of blank test (zero concentration) sample; α--slope (absorbance·ml/g) and intercept of the standard curve measured according to Section 7.|; V-volume of absorption liquid for sampling.ml
V-volume of deep sample converted to standard state (101.3 kPa, 273 K).L;C. -Concentration of NO. standard mixed gas passing through the sampling system.mg/m (101.3kPa.273K)tB1
GB/T15436-1995
The f value is affected by factors such as NO. concentration in the air, sampling flow, absorption bottle type, sampling efficiency, etc. Therefore, when measuring the f value, the measurement conditions should be kept consistent with the actual sampling conditions. Additional notes:
This standard was proposed by the Science and Technology Standards Department of the State Environmental Protection Administration. This standard was drafted by the Zhenyang City Environmental Monitoring Center Station. The main drafters of this standard are Wang Yuping, Chen Tao, Wang Juan, Li Jing, and Cao Kun.- A -a) XV×D
8. 2 Concentration of nitrogen monohydride in the air (in terms of NO,): Co - (Az-AO)XV×D
bxfxkxV.
8.3 Calculation of the concentration of ammonia oxides in the air: Chx), = Ch, - Ch
Wherein: CNO——
concentration of nitrogen dioxide in the air, mg/m~, CNo
concentration of nitric oxide in the air (in terms of NO2), mg/m; concentration of nitrogen oxides in the air (in terms of NO:), mg/m14:-——the absorbance of the samples in the first and second absorption bottles connected in series, Au
the absorbance of the blank test sample;
the slope (absorbance·mI,/) and intercept of the standard curve measured in Section 7.1: *+++**+++++++++++++++++++(1)
..(2
Vthe volume of the absorption liquid for sampling, mL:
GE/T 15436—1995
V.—Converted to the sampling volume under the standard state (101.3kPa, 373K), LR——NO-NO. Oxidation coefficient. 0.68
D Dilution factor of the sample:
f-Saltzmam experimental coefficient, 0.88 (When the concentration of nitrogen dioxide in the air is higher than 0.720mg/m3, the factory value is 0.77) 9 Precision and accuracy
9.1 Determination of NO, precision and accuracy of standard gas Five laboratories measured NO standard gas with a concentration range of 0.056~0.480g/m3 Gas, repeatability coefficient of variation is less than 10%, relative error is less than 8%.
9.2 Determination of precision and accuracy of NO standard gas Determination of NO standard gas with a concentration range of 0.057~-0.396mg/m3, repeatability coefficient of variation is less than 10%, relative error is less than ±10%.
Part 2 Lead trioxide-quartz sand oxidation method
10 Principle
Nitrogen oxides in the air pass through the blue chromium oxide-quartz sand oxidation tube, and react with the amino acid in the absorption liquid in the form of nitrogen dioxide, and then react with N-(1-naphthyl) ethylamine The hydrochloride is coupled to generate a pink azo dye, and the absorbance is measured at a wavelength of 540-545nm.
11 Reagents and materials
Chromium trioxide-quartz sand oxidation: sieve 20-40 days of quartz sand, soak it in (1+2) hydrochloric acid solution overnight, wash it with water until it is neutral, and dry it. Mix chromium trioxide and quartz sand in a mass ratio of (1+20), add a small amount of water to mix well, and dry
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