GB/T 8914-1988 Standard method for testing mercury in the atmosphere of residential areas - Gold amalgam enrichment/atomic absorption method
Some standard content:
National Standard of the People's Republic of China
Hygienic determination method of mercury in air of residential areas -Gold amalgamation-atomic adsorption spectrometric method
Hygienic determination method of mercury in air of residential areas -Gold amalgamation-atomic adsorption spectrometric method1Scope of application
This standard applies to the determination of mass concentration in the atmosphere of residential areas. 1.1Sensitivity
6×10-10g (1% absorption).
1.2Lower limit of detection
Sampling at a flow rate of 1L/min, sampling for 1h, the lowest detection concentration is 0.01μg/m3. 1.3Determination range
Select the measuring instrument range I, Ⅱ according to different concentration ranges. The linear range of range I is 0.0006~0.06μg, applicable to 0.01~1μg/m2; the linear range of range II is 0.006~0.6μg, applicable to 0.1~10μg/m. 1.4+ Interference and elimination
UDC614.78:613
.15:546.49
GB8914-88
1.4.1 Organic vapors such as benzene and ketone enter the absorption cell of the measuring instrument and can also absorb 253.7nm ultraviolet rays, which can cause positive errors. However, since the gold film mercury enrichment tube is used for sampling, these organic vapors are not retained on the gold film, so the interference of these organic vapors can be eliminated. 1.4.2 If the enrichment tube is contaminated by oil mist, water vapor, etc., the enrichment tube will be "poisoned", resulting in incomplete enrichment and incomplete release. At this time, the enrichment tube can be regenerated. The method is to insert the tube into the "desorption" hole, adjust the desorption time to 2min, desorb, and repeat to vaporize and remove impurities.
2 Principle
Mercury and gold come into contact to form amalgam, enrich trace mercury in the air, and then quantitatively release atomic gold at high temperature, which is blown into the water measuring instrument by carrier gas, and quantitatively measured by the absorption of gold vapor at a wavelength of 253.7nm. 3 Reagentswww.bzxz.net
3.1 Gold film particles: weigh 0.2g fluoroauric acid (HAuCl, 3H, O) and dissolve it in 50ml distilled water, add 5g quartz sand (50~80 mesh), stir evenly, dry it in a boiling water bath, then put it in a quartz tube, heat it to more than 800℃ in a tubular electric furnace, and blow in purified air at the same time to decompose chloroauric acid and form a thin layer of gold film on the surface of quartz sand, cool it in a desiccator, and bottle it for later use. 3.20.2mol/L sulfuric acid solution.
3.330% stannous chloride solution: weigh 30g stannous chloride (SnCl2H2O) and dissolve it in 25ml hydrochloric acid, dilute to 100ml with water. Then pass purified air (or nitrogen) into the solution to remove the background mercury. 3.4 Mercury standard solution: accurately weigh 1.3537g mercury dichloride, dissolve it in 0.05mol/L sulfuric acid solution, transfer it to a 1000ml volumetric flask, and dilute to the scale. This solution contains 1mg mercury in 1ml. Dilute it to a standard solution containing 0.1μg mercury in 1ml before use, or directly purchase standard mercury solution (safe packaging) for use.
Approved by the Ministry of Health of the People's Republic of China on February 23, 1988, and implemented on December 1, 1988
4 Instruments and Equipment
GB8914-88
4.1 Gold film microparticle mercury enrichment tube (referred to as enrichment tube): a quartz tube with an inner diameter of 5mm and a length of 17cm, with 10mm long gold film microparticles (about 0.45g) in the middle, and quartz wool plugged at both ends. The saturation absorption capacity of the tube for mercury is 1μg. 4.2 Constant flow sampling pump: flow range 0.2~1.5L/min. And the flow is stable and adjustable, and the constant flow error is less than 2%. 4.3 Mercury vapor tail gas absorption purifier: iodine-containing activated carbon (preparation see Appendix A) tube. 4:4
Permanent enrichment-desorber: enrichment time control range is 0.5min±2s; 1min±2s, 2min±4s; 5min±6s, 15min±10s; 30min±90s, 60min±3min; desorption time is 5~60s continuously adjustable. 4.5
Ten drying tube: anhydrous calcium chloride tube.
4.6 Mercury vapor generating tube: 50ml capacity.
4.7 Mercury analyzer: cold atomic absorption mercury vapor measuring instrument. Recorder: automatic semi-balanced recorder, 1mV or 5mV. 4.8
5 Sampling
Connect the enrichment tube treated by expulsion to the air inlet of the sampler, so that the enrichment tube is in a vertical position with the air inlet facing upwards, and collect 60L of gas at a flow rate of 1L/min. Before and after sampling, the flow rate of the sampling system should be calibrated with a soap film flowmeter, with an error of no more than 5%. According to the concentration of mercury in the air, the amount of gas collected should be appropriately increased or decreased. The method of expulsion treatment is to desorb and release the enrichment tube on the desorber. Record the temperature and atmospheric pressure of the sampling point during sampling. 6 Operation steps
6.1 Connect the instrument gas system according to the figure below. Check that the gas line is leak-free. Adjust the flow rate of enrichment and desorption to 0.8L/min. After the instrument is running stably, the measurement can be carried out. ?
Gas flow chart of permanent steam determination
1-air purification chamber membrane particle recorder enrichment symbol; 2-mercury vapor generating bottle; 3-enrichment tube during desorption; 4-enrichment tube during desorption; 5-enrichment-desorber; 6-electromagnetic gas circuit conversion valve; 7-flow meter; 8-drying tube; 9-measurement instrument; 10-recorder, 11-absorption purifier, 12-vacuum pump 6.2 Preparation of standard curve
6.2.1 Take 6 test tubes and prepare standard series according to the following table: tube
standard solution, ml
0.2mol/L sulfuric acid, ml
water content, μg||t t||GB8914—88
Add the standard solutions in each tube into the mercury vapor generating bottle in turn. Connect the mercury vapor generating bottle to the enrichment tube. Insert the enrichment tube into the "enrichment" hole of the enrichment-desorber. Turn the flow switch of the enrichment-desorber to the "enrichment" gear, and adjust the enrichment time to 2 minutes. Add 0.3 ml of 30% stannous chloride solution into the mercury vapor generating tube, and immediately press the "start" switch. The instrument will automatically enrich and stop automatically after 2 minutes. 6.2.2 Remove the mercury enrichment tube, insert it into the "desorption" hole, and turn the flow switch of the enrichment-desorber to the "desorption" gear. Adjust the desorption time to 25 seconds (depending on factors such as air temperature at 2 0～30s are adjustable). Press the "start" switch, the instrument will automatically desorb, and a peak value can be obtained on the recorder. The standard curve is drawn with the peak height against the mercury content (μg). 6.3 Sample determination
Insert the enrichment tube with sample into the "desorption" hole of the mercury enrichment-desorber, and turn the flow switch of the enrichment-desorber to the "desorption" gear. The following operation is performed according to 6.2.2 in the preparation of the standard curve to measure the content (μg) in the sample enrichment tube. After desorption, all the mercury is driven out of the enrichment tube, so it can be sampled for the second time after cooling. To prevent contamination, the enrichment tube is sealed at both ends when it is stored. After repeated use of the enrichment tube, the gold film particles The quartz tube may become loose, which will affect the enrichment effect. Please make sure it is plugged tightly when using it. 7. Calculation of results
7.1 Convert the sampling volume into the sampling volume under standard conditions according to formula (1). Vo=V
Wherein: Vo
sampling volume under standard conditions, L;
sampling volume, L;
-absolute temperature under standard conditions, 273K;
temperature of the sampling point during sampling, ℃;
-atmospheric pressure under standard conditions, 101kPa (or 760mmHg); atmospheric pressure at the sampling point during sampling, kPa (or mmHg). 7.2 The mass concentration of mercury in the air is calculated according to formula (2): C=
Wherein: C——mercury concentration, μg/m3;
The mercury content measured in the enrichment tube, ug.
8Precision
Qx1000
The relative standard deviation of the same sample (sample content is 35ngHg) measured 6 times with one mercury enrichment tube is not more than 1%. The relative standard deviation of the same sample measured with 6 different mercury enrichment tubes is not more than 5%. (1)
（2）
GB8914—88
Appendix A
Preparation of iodine-containing activated carbon
(Supplement)
Weigh 1 part by weight of iodine, 2 parts by weight of potassium iodide and 20 parts by weight of water to make a solution, then add about 10 parts by weight of activated carbon, stir vigorously until the solution is decolorized, filter the solution with a cloth, take out the activated carbon, and then dry it at 110℃ for 1~2h, take it out, seal it in a brown bottle and store it for later use.
Additional remarks:
This standard was proposed by the Environmental Health Standard Subcommittee of the National Health Standard Technical Committee. This standard was drafted by the School of Public Health of Shanghai Medical University, Guizhou Provincial Environmental Health Monitoring Station, and Shandong Provincial Health and Epidemic Prevention Station. The main drafter of this standard was Ma Xiaojie.
This standard is interpreted by the Environmental Health Monitoring Institute of the Chinese Academy of Preventive Medicine, the technical coordination unit entrusted by the Ministry of Health. 414
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