GB/T 16128-1995 Standard method for the examination of sulfur dioxide in the atmosphere of residential areas - formaldehyde solution absorption-pararosaniline hydrochloride spectrophotometric method
Some standard content:
ICS_13.040.20
National Standard of the People's Republic of China
GB/T1612.8--1995
Standard method for hygienic examinationof sulfur dioxide in air of residential areas-Formaldehyde solution sampling-pararosanilinehydrocloride spectrophotometric methodPublished on January 23, 1996
State Administration of Technical Supervision
Ministry of Health of the People's Republic of China
Implemented on July 1, 1996
National Standard of the People's Republic of China
Standard method for hygienic examinationof sulfur dioxide in air of residential areas-Formaldehyde solution sampling-pararosanilinehydrocloride spectrophotometric method ofsulfur dioxide in air of residential areas-Formaldehydesolution sampling-pararosanilinehydrocloride spectrophotometric method1 Subject content and scope of application
GB/T16128—1995
This standard specifies the determination of sulfur dioxide concentration in the atmosphere of residential areas by formaldehyde solution absorption-pararosaniline hydrochloride spectrophotometric method. This standard applies to the determination of sulfur dioxide concentration in the atmosphere of residential areas, and also to the determination of sulfur dioxide concentration in the air of indoor and public places.
2 Reference standards
Preparation of mixed gas for gas analysis calibration weighing method GB5275
GB8913 Hygienic standard for sulfur dioxide in the atmosphere of residential areas Tetrachloromercuric salt pararosaniline hydrochloride spectrophotometric method 3 Principle
Sulfur dioxide in the air is absorbed by formaldehyde buffer solution to generate stable hydroxymethylsulfonic acid, which reacts with pararosaniline hydrochloride after adding alkali to generate purple-red compound, which is quantified by colorimetry. 4 Reagents and Materials
The purity of the reagents used in this method is analytically pure unless otherwise specified. Water is double distilled water or deionized water; primary water from a quartz distiller can also be used.
4.1 Absorption solution (formaldehyde-potassium hydrogen phthalate buffer) 4.1.1 Stock solution: Weigh 2.04g potassium hydrogen phthalate and 0.364g disodium ethylenediaminetetraacetic acid (EDTA-2Na for short) and dissolve in water, transfer to a 1L volumetric flask, add 5.30mL 37% formaldehyde solution, and dilute to scale with water. Store in a refrigerator and it can be stored for one year. 4.1.2 Working solution: When using, dilute the above absorption stock solution 10 times with water. 4.22mol/L sodium hydroxide solution: Weigh 8.0g sodium hydroxide and dissolve in 100mL water. 4.30.3% sodium sulfamic acid solution: weigh 0.3g sulfamic acid, add 3.0mL 2mol/L sodium hydroxide solution, dilute with water to 100mL.
4.40.025% pararosaniline hydrochloride solution. 4.4.11mol/L hydrochloric acid solution: measure 86mL of concentrated hydrochloric acid (superior purity, P20=1.19g/mL), dilute with water to 1000mL. 4.4.24.5mol/L phosphoric acid solution: measure 307mL of concentrated phosphoric acid (superior purity, P20=1.69g/mL), dilute with water to 1L. Approved by the State Administration of Technical Supervision on December 15, 1995, and implemented on July 1, 1996
GB/T-16128—1995
4.4.3 0.25% pararosaniline hydrochloride stock solution 1): Weigh 0.125g pararosaniline hydrochloride (PRA, C1gH18N3Cl·3HCl), purify according to Appendix A, and dilute to 50mL with 1mol/L hydrochloric acid solution. 4.4.4 0.0 25% pararosaniline hydrochloride working solution: Take 25mL of 0.25% stock solution, transfer to a 250mL volumetric flask, dilute to the mark with 4.5mol/L phosphoric acid solution, and use after 24 hours. This solution should be sealed and stored away from light and can be used for 9 months. Note: 1) If there is a commercially available 0.25% PRA stock solution, it can be directly diluted and used. 4.5 Sulfur dioxide standard solution
4.5.1: Sulfur dioxide standard stock solution: Weigh 0.2g sodium sulfite (Na2SO3) and 0.01g disodium ethylenediaminetetraacetic acid (EDTA2Na) and dissolve them in 200mL of freshly boiled and cooled water. This solution contains 320-400μg sulfur dioxide per milliliter. The solution needs to be left for 2-3 hours before calibrating its accurate concentration. The calibration method is the same as Appendix B of GB8913. According to the calibration calculation results, immediately dilute with absorption liquid to a standard stock solution containing 25μg sulfur dioxide per milliliter, which can be stored in a refrigerator for three months. 4.5.2 Sulfur dioxide standard working solution: Dilute the standard stock solution with absorption liquid to a standard working solution containing 5ug sulfur dioxide per milliliter, which can be stored in a refrigerator for one month. It can be stored for 3 days at room temperature below 25℃. 5 Instruments and equipment
5.1 Absorption tube: Ordinary porous glass plate absorption tube, can hold 10mL absorption liquid, used for 30-60min sampling; large porous glass plate absorption tube can hold 50mL absorption liquid, used for 24h sampling. 5.2 Air sampler: flow range 0.1-1L/min, stable flow. When in use, use soap film flowmeter to calibrate the flow of the sampling series before and after sampling, and the flow error should be less than 5%. 5.3 Stoppered colorimetric tube: 25mL.
5.4 Spectrophotometer: Use 10mm colorimetric blood and measure absorbance at a wavelength of 570nm. 5.5 Constant temperature water bath (0-40℃): The temperature error must be controllable within ±1℃. 5.6 Adjustable quantitative liquid doser: 5mL, inner diameter of the dosing tube mouth 1.5-2mm. 6 Sampling
6.130~60min sample
Use ordinary porous glass plate absorption tube, fill with 8mL absorption liquid, and sample at a flow rate of 0.5L/min for 30~60min. 6.224h sample
Use large porous glass plate absorption tube, fill with 50mL absorption liquid, and sample at a flow rate of 0.2~0.3L/min for 24h. The absorption liquid temperature should be kept below 30℃ during sampling; avoid direct sunlight exposure to samples during sampling, transportation and storage. Record the air temperature and atmospheric pressure at the sampling point in time. When the air temperature is higher than 30℃, if the sample cannot be analyzed on the same day, it should be stored in a refrigerator. 7'Analysis steps
7.1. Drawing of standard curve
7.1.1. Draw the standard curve using sulfur dioxide standard working solution. 7.1.1.1 Use 6 25mL colorimetric tubes to prepare the standard series according to Table 1. Table 1 Sulfur dioxide standard series
Standard working solution, mL
Absorption solution, mL
Sulfur dioxide content, ug
Add 1.0mL of 0.3% sodium ammonium sulfonate solution, 0.5mL of 2.0mol/L sodium hydroxide solution and 1mL of water to each tube respectively, mix thoroughly, then use an adjustable quantitative liquid dosing device to quickly inject 2.5mL of 0.025% PRA solution into the mixed solution, immediately cover the stopper and invert to mix (if there is no adjustable quantitative liquid dosing device, the PRA solution can also be added inverted: mix the mixed solution of sodium ammonium sulfonate solution, sodium hydroxide solution and water, and then pour it into another set of colorimetric tubes pre-loaded with 2.5mL of 0.025% PRA solution, immediately cover the stopper and invert to mix), and put it into a constant temperature water bath for color development. According to the room temperature in different seasons, the color development temperature and time closest to the room temperature can be selected from Table 2. Table 2 Color development temperature and time
Color development temperature, ℃
Color development time, min
Stable time, min
7.1.1.2 At a wavelength of 570nm, use 10mm colorimetric blood and water as a reference to determine the absorbance. Draw a standard curve with absorbance versus sulfur dioxide content (ug), and calculate the slope of the regression line. The slope of the standard curve 6 should be 0.035±0.003 absorbance/μg sulfur dioxide. The correlation coefficient should be greater than 0.999. The reciprocal of the slope is used as the calculation factor B, (μg/absorbance) for sample determination. 7.1.2 Drawing a standard curve using sulfur dioxide standard gas For the device and method of preparing standard gas using a permeation tube, refer to GB5275. 7.1.2.1 The specific operation of sampling standard gas of different concentrations is the same as 6.1.2.1 of GB8913. 7.1.2.2.Transfer the sample of each concentration of standard gas into a 25mL colorimetric tube, and determine the absorbance of each concentration of standard gas according to the operating steps of 7.1.1 for drawing a standard curve with standard working solution. Draw a standard curve with absorbance versus the concentration of sulfur dioxide standard gas (uig/m\), and the reciprocal of the slope 6 B is the calculation factor for sample determination. 7.2 Sample determination
7.2.1 After sampling, if particulate matter is found in the sample solution, it should be removed by centrifugation. 7.2.1.130~60min sample: The sample solution in the absorption tube can be directly transferred into a 25mL colorimetric tube, and the absorption tube can be washed twice with 2mL absorption liquid, and the washing liquid is combined in the colorimetric tube, and the volume of the absorption liquid is supplemented to 10mL with water. Let it stand for 20 minutes to allow the ozone to completely decompose before analysis.
7.2.1.224h sample: Make up the sample to 50mL with water, mix well, take 10mL into a 25mL colorimetric tube, place for 20min and analyze.
7.2.2 While measuring each batch of samples, use 10mL of unsampled absorption solution as a reagent blank, and prepare a standard control tube containing 10ug sulfur dioxide for quality control in sample analysis. 7.2.3 The sample solution, reagent blank and standard control tube are measured according to 7.1.1. The measurement conditions of the sample should be consistent with the measurement conditions of the standard curve. 8 Result calculation
8.1 Convert the sampling volume into the sampling volume under standard conditions according to formula (1). V. =V.××
Where: V. — sampling volume under standard conditions, L; V. — sampling volume, obtained by multiplying the gas flow rate by the sampling time, L; T. ——absolute temperature of standard conditions, 273K; po—atmospheric pressure of standard conditions, 101.3 kPa; p—atmospheric pressure at sampling, kPa;
air temperature at sampling, °C.
8.2·Calculation of sulfur dioxide concentration in air (1)
GB/T16128—1995
8.2.1When preparing the standard curve with sulfur dioxide standard solution, calculate the sample concentration using formula (2). (A-Ao)×B×D
Where: c-
concentration of sulfur dioxide, mg/m\;
absorbance of sample;
absorbance of reagent blank
calculation factor obtained from 7.1.1, ug/absorbance; B,
dilution factor (1 for 30~60min sample, 5 for 24h sample). When the standard curve is prepared with sulfur dioxide standard gas, the sample concentration is calculated using formula (3). 8.2.2
(AA)×B
Wherein: c
Sulfur dioxide concentration, mg/m2;
Sample absorbance:
Reagent blank absorbance;
Calculation factor, Hg/(m2.absorbance). Be
9. Precision and accuracy
.(2)
(3)
9.1 Reproducibility of the method: When the standard curve is prepared with the standard solution, the average relative standard deviation of repeated measurements at each concentration point is 4.5%; the relative standard deviation of repeated measurements of the 5μg/10mL standard sample is less than 5%; when the concentration of the standard gas is 100~200μg/m, the relative error between the measured value and the standard value is less than 20%. 9.2 The sample spike recovery rate is 101% (n=13). 9.3 Sensitivity
10mL absorption solution contains 1μg of sulfur dioxide and should have an absorbance of 0.035±0.003. 9.4 Detection limit
The detection limit is 0.3μg/10mL (calculated as the concentration corresponding to the absorbance of 0.01). If the sampling volume is 20L, the minimum detection concentration is 0.015mg/m. When 50mL absorption solution is used, the 24h sampling volume is 300L, and 10mL sample solution is taken for determination, the minimum detection concentration is 0.005mg/m.
9.5 Measurement range
The measurement range is 0.3~20μg sulfur dioxide in 10mL sample solution. If the sampling volume is 20L, the measurable concentration range is 0.015~1mg/m2.
9.6 Interference and Elimination
Certain heavy metals, ozone and nitrogen oxides at normal concentration levels in the air do not interfere with the determination of this method. When 10mL of sample solution contains 1μgMn2+ or more than 0.3μgCrs+, there will be negative interference to the determination of this method. Adding disodium cyclohexanediaminetetraacetic acid (abbreviated as CDTA) can eliminate the interference of Mn2+ with a concentration of 2μg/10mL; increasing the amount of alkali added in this method (such as adding 1.5mL of 2.0mol/L sodium hydroxide solution) can eliminate the interference of Cr6+ with a concentration of 1μg/10mL. In order to reduce the interference of Cr6+, all glassware used in this method must not be treated with chromic acid solution but should be soaked in 10% hydrochloric acid solution and then washed and dried before use.
10 Precautions
10.1 This method overcomes the strict requirements of tetrachloromercuric salt absorption-pararosaniline hydrochloride spectrophotometry on color development temperature. The suitable color development temperature range is wide (1525℃) and can be selected according to room temperature. However, the sample should be color-determined under the same temperature and time conditions as the standard curve. 10.2 When the manganese content in the atmosphere of the sampling area is high, the absorption solution should be prepared according to the following steps. 10.2.10.05mol/L disodium cyclohexanediaminetetraacetic acid solution: Weigh 1.82g trans-1.2-cyclohexanediaminetetraacetic acid (tans-1,2-cyclohexanediaminetetraacetic acid, hereinafter referred to as CDTA) and dissolve it in 5.0mL 2mol/L sodium hydroxide solution, and dilute it to 100mL with water.
10.2.2 0.001mol/L CDTA application solution: dilute 0.05mol/L CDTA solution 50 times. 10.2.3 Working solution: when using, mix the absorption solution stock solution (4.1.1) and CDTA application solution in a ratio of 1:1, and then dilute the mixture 5 times with water.
GB/T16128-1995
Appendix A
Purification of pararosaniline hydrochloride
(Supplement)
A1 Take 500mL of n-butanol and 1.0mol/L hydrochloric acid solution, put them into a 1000mL separatory funnel, shake for 3-5min, make them mutually dissolve and reach equilibrium, and separate them for use.
A2 Weigh 0.125g of phenylamine hydrochloride (PRAC1gH1sNCl·3HCl for short), put it into a 100mL beaker, add 50mL of balanced 1.0mol/L hydrochloric acid solution, and transfer it into a 250mL separatory funnel after it is completely dissolved. A3 Wash the beaker several times with 80mL of balanced n-butanol, add the washing liquid into the same separatory funnel, shake for 3 minutes, and let it stand to separate. A4 Put the lower aqueous phase into another 250mL separatory funnel, add 40mL of balanced n-butanol, and extract it repeatedly 8 to 10 times according to the above method, filter the aqueous phase into a 50mL volumetric flask, dilute it to the scale with 1.0mol/L hydrochloric acid solution, and shake it well. This PRA stock solution is orange-yellow. A5 Stock solution purity test
A5.1PRA solution has a maximum absorption peak at a wavelength of 540nm in acetic acid-sodium acetate buffer solution. Take 1mE of the stock solution and dilute it to 100mL with water. Take 5mL of this dilution in a 50mL volumetric flask, add 5mL of 1.0mol/L acetic acid-sodium acetate buffer, dilute to scale with water, and measure the absorption peak after 1 hour. A5.2 Use 0.25% PRA stock solution to prepare 0.025% PRA working solution according to 3.4.4 for reagent blank determination (see 7.1), the absorbance shall not exceed the limit value in Table A1:
Table A1 Limit values of absorbance at different temperatures
Temperature, ℃
Temperature, ℃
See Appendix B of GB8913.
Additional notes:
GB/T16128—1995
Appendix B
Standardization method for sulfur dioxide concentration in sulfur dioxide standard solution (supplement)
This standard is proposed by the Ministry of Health of the People's Republic of China. This standard is drafted by Wuhan Municipal Health and Epidemic Prevention Station, Environmental Sanitation Monitoring Institute of Chinese Academy of Preventive Medicine, Hebei Provincial Health and Epidemic Prevention Station, Guangzhou Municipal Health and Epidemic Prevention Station, and Harbin Municipal Health and Epidemic Prevention Station. The main drafters of this standard: Li Yubing, Chen Wenge, Pang Lianque, Deng Suqing, Jiang Guangzeng, Shi Liwei This standard is interpreted by the Environmental Sanitation Monitoring Institute of Chinese Academy of Preventive Medicine, which is entrusted by the Ministry of Health. The People's Republic of ChinawwW.bzxz.Net
National Standard
Sanitary Sulfur Dioxide in the Atmosphere of Residential Areas
Standard Method for Inspection Formaldehyde Solution Absorption
-Pararosaniline Hydrochloride Spectrophotometric Method
GB/T16128-1995
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Format 880×1230·1/16 Printing sheet 3/4 Number of words 11,000 First edition December 1996·First printing December 1996 Number of copies 1-2000
Book number: 155066·1-13284. Price RMB 6.00*
Headings 300-35
161219/
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