HJ 542-2009Ambient air. Determination of mercury and its compounds. Cold atomic fluorescent spectrophotometry after sulfhydryl cotton preconcentraction (English PDF)

Foreword

To protect the environment and protect people in order to implement the Environmental Protection Law of the People's Republic of China and the Law of the People's Republic of China on the Prevention and Control of Air Pollution this standard is established for the health of the body and the monitoring methods for the regulation of mercury and its compounds in the ambient air.

This standard specifies the enthalpy-based cotton enrichment cold atomic fluorescence spectrophotometry for the determination of mercury and its compounds in ambient air.

Appendix A and Appendix B of this standard are informative annexes.

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

This standard was drafted. Beijing Environmental Protection Monitoring Center.

This standard was approved by the Ministry of Environmental Protection on December 30, 2009.

This standard has been implemented since April 1, 2010.

This standard is explained by the Ministry of Environmental Protection.

Determination of mercury in ambient air Sulfhydryl Cotton Enrichment-Cold Atomic Fluorescence Spectrophotometry (Provisional)

1 Scope of application

This standard specifies the sulfhydryl cotton enrichment-cold atomic fluorescence spectrophotometry for the determination of mercury and its compounds in ambient air.

This standard applies to the determination of mercury and its compounds in ambient air.

The detection limit of this standard method is 0.1 ng/10 ml sample solution. When the sampling volume is 15 L, the detection limit is 6.6×10-6 mg/m3.

The lower limit is 2.6 × 10-5 mg/m3.

2 Normative references

The contents of this standard refer to the terms in the following documents. For undated references, the valid version applies to this standard.

HJ/T 194 Technical Specifications for Manual Air Quality Monitoring GB/T 6682 Analytical laboratory water specifications and test methods

3 Principle of the method

In a slightly acidic medium, mercapto cotton is used to enrich mercury and its compounds in ambient air.

The inorganic mercury reaction formula is as follows.

Hg2 2H SR Hg

The organic mercury reaction formula is as follows.

CH3HgCl H-SR CH3Hg-SR HCl when elemental mercury passes through the sulfhydryl cotton sampling tube, it is mainly physical adsorption and chemical adsorption of monolayers.

After sampling, total mercury was desorbed with a 4.0 mol/L hydrochloric acid-sodium chloride saturated solution, reduced to metallic mercury by stannous chloride, and measured by cold atomic fluorescence.

The mercury meter measures the total mercury content.

4 Reagents and materials

Unless otherwise stated, analytically pure reagents that meet national standards were used for the analysis. Water, GB/T 6682, two.

4.1 High purity nitrogen. phi = 99.999%.

4.2 Potassium dichromate (K2Cr2O7). excellent grade pure.

4.3 Sulfuric acid. rho (H2SO4) = 1.84 g/ml, excellent grade pure.

4.4 Hydrochloric acid. rho (HCl) = 1.19 g/ml, excellent grade pure.

4.5 Nitric acid. rho (HNO3) = 1.42 g/ml, excellent grade pure.

4.6 Potassium dichromate solution. w (K2Cr2O7) = 1.0%.

Weigh 1.0 g of potassium dichromate (4.2), dissolve in water, and dilute to 100 ml.

4.7 Sulfuric acid solution. phi (H2SO4) = 10%.

Measure 10 ml of concentrated sulfuric acid (4.3) and slowly add 90 ml of water.

4.8 Hydrochloric acid solution. c (HCl) = 4.0 mol/L.

Measure 123 ml of hydrochloric acid (4.4), dilute to 1 000 ml with water, and mix.

4.9 Hydrochloric acid solution. c (HCl) = 2.0 mol/L.

Measure 12 ml of hydrochloric acid (4.4), dilute to 1 000 ml with water, and mix.

4.10 Hydrochloric acid solution. pH=3.

Pipette 2.0 mol/L hydrochloric acid (4.9) 0.50 ml, dilute with water to 1 000 ml, and mix.

4.11 Nitric acid solution. phi (HNO3) = 10%.

Measure 10 ml of concentrated nitric acid (4.5), dilute to 100 ml with water, and mix.

5 Instruments and equipment

Unless otherwise stated, the analysis uses a Class A glass gauge that complies with national standards.

5.1 Air sampler. The flow range is 0~1 L/min.

5.2 Cold atomic fluorescence mercury detector.

5.3 base cotton sampling tube. quartz, as shown in Figure 1.

Unit. mm

Figure 1 Quartz sampling tube

Weigh 0.1 g of sulphur-based cotton, insert it into the tube from the large diameter end of the quartz sampling tube, and press it into the tube section with an inner diameter of 6 mm.

It is about 3 cm. The sulfhydryl cotton was acidified with 0.40 ml of a hydrochloric acid solution (4.10) of pH=3 immediately before use. The ends of the sulphur-based cotton sampling tube shall be sealed with a sleeve.

Store in a mercury-free container.

5.4 Buchner funnel.

5.5 Filtering device.

5.6 Oven.

5.7 Mercury reaction bottle. 5 ml.

5.8 Syringe. 50 µl, 1 ml.

6 Samples

7 Analysis steps

8 Calculation of results

Calculate the mercury content in ambient air according to formula (1).

rho (Hg)= 0

And 1000

WWV

Where. rho (Hg) - the amount of mercury in the ambient air, mg/m3;

W--the amount of mercury in the sample taken during the measurement, ng;

W0--the content of mercury in the blank taken during the measurement, ng;

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

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

Vnd - the sampling volume under standard conditions (101.325 kPa, 273 K), L.

9 Quality Assurance and Quality Control

9.1 Quality assurance and quality control are carried out in accordance with HJ/T 194.

9.2 Test reagents, including sulfhydryl cotton (4.18), 10% stannous chloride solution (4.15), pH=3 hydrochloric acid solution (4.10), Potassium bromate-potassium bromide solution (4.13), hydroxylamine hydrochloride-sodium chloride solution (4.14) and 4.0 mol/L hydrochloric acid-sodium chloride saturated solution (4.12) Etc., all need to be checked by cold atomic fluorescence mercury detector in advance, the blank value of mercury in the reagent should not exceed 0.1 ng.

9.3 The mercury recovery test is carried out after the preparation of each batch of thiol cotton (see Appendix A).

10 Precautions

10.1 Hydroxylamine hydrochloride often contains mercury and must be purified. When the mercury content is low, the mercapto-based cotton fiber tube is used for mercury removal; when the mercury content is high, first press the extraction method removes a large amount of mercury and then removes mercury according to the sulfhydryl cotton fiber tube method (see Appendix B).

10.2 If the organic mercury and inorganic mercury are to be separately measured, after sampling, place the sulphur-based cotton sampling tube on the bottle mouth of the 5 ml volumetric flask at 1 ml/min.

At the flow rate, 2.0 mol/L hydrochloric acid solution (4.9) was added dropwise to desorb organic mercury. Dilute to the mark with 2.0 mol/L hydrochloric acid solution (4.9), the following steps the same drawing of the standard curve. Continue to desorb the inorganic mercury from the above sampling tube with 4.0 mol/L hydrochloric acid-sodium chloride saturated solution (4.12).

The same as before.

10.3 The method can also measure particulate mercury and gaseous mercury separately, and can add an organic cellulose microporous membrane to capture the sulfhydryl cotton sampling tube.

Granular mercury. It was dissolved in a 10% nitric acid solution (4.11), and mercury was measured by the above method.

Appendix A

(informative appendix) Determination of adsorption efficiency of sulfhydryl cotton Add mercury chloride standard solution (4.17) to stannous chloride hydrochloric acid solution (4.15), and then use nitrogen (4.1) to produce Elemental mercury is introduced into the sulphur-based cotton sampling tube. Desorbed with 4.0 mol/L hydrochloric acid-sodium chloride saturated solution (4.12), and the recovery was determined to obtain a sulfhydryl group.

The adsorption efficiency of cotton on mercury.

Place 1 000 mg/kg methylmercury (CH3HgCl) in a 100 ml polyethylene bottle with a silicone rubber stopper, sealed and kept at temperature it is 22 ° C. At this time, the concentration of methylmercury in the vapor is 27.8 ng/ml±4.1 ng/ml, and a certain volume of vapor is extracted with a gas-tight syringe.

The sample gas flow is injected into the sputum-based cotton sampling tube, and the organic mercury is desorbed with a 2.0 mol/L hydrochloric acid (4.9) solution, and the recovery rate is determined to obtain a thiol cotton pair.

The adsorption efficiency of organic mercury.

Appendix B

(informative appendix) Mercury removal method Mercury-based cotton fiber tube mercury removal method. a glass tube with an inner diameter of 6 to 8 mm and a length of about 100 mm, one end of which is thinned, or a liquid leakage of 500 ml Fill the liquid pipe with 0.1~0.2 g sulphur-based cotton fiber (4.18), and remove the reagent to be purified by flowing once or twice at a rate of 10 ml/min.

Do not use mercury.

Extraction method. 250 ml of hydroxylamine hydrochloride solution was injected into a 500 ml separatory funnel, each time adding 15 ml of diphenylthiobarium (disulfide) 腙C13H12N4S) 0.1 g/L carbon tetrachloride (CCl4) solution, repeated extraction until the dithizone-containing carbon tetrachloride solution remains green the color remains the same. It is then extracted with carbon tetrachloride to remove excess dithizone.