Determination of hydrogen fluoride in exhaust gas from fixed pollution sources by ion chromatography method

Warning: Hydrogen fluoride is harmful to human health. When sampling, precautions should be taken to avoid inhalation or contact with skin and eyes.

1 Scope of application

This standard specifies the ion chromatography method for determining hydrogen fluoride in exhaust gases from fixed pollution sources. This standard is applicable to the determination of hydrogen fluoride in exhaust gases from fixed pollution sources. When the sampling volume is 20 L (standard state) and the constant volume is 100 ml, the detection limit of the method is 0.08 mg/m3, and the lower limit of determination is 0.32 mg/m3.

2 Normative References

This standard refers to the following documents or their clauses. The valid version of any referenced document without a date is applicable to this standard. GB/T 16157 Determination of particulate matter and sampling methods for gaseous pollutants in exhaust gas from fixed sources HJ/T 47 Technical conditions for flue gas samplers HJ/T 48 Technical conditions for flue gas samplers HJ/T 397 Technical specifications for monitoring fixed source exhaust gas

3 Terms and definitions

The following terms and definitions apply to this standard. Hydrogen fluoride, as measured in this standard, refers to inorganic fluorides such as hydrogen fluoride and silicon tetrafluoride that exist in gaseous or droplet form (calculated as hydrogen fluoride).

4 Methods and Principles

Use a heated sampling tube to collect exhaust gas samples, and filter out particulate matter through a heated filter membrane. The hydrogen fluoride in the exhaust gas sample is absorbed by the alkaline absorption solution to generate fluoride ions. Sample injection into ion chromatography for separation and detection, qualitative analysis based on retention time, and quantitative analysis based on peak area or peak height.

5 Interference and Elimination

5.1 Particulate fluoride can interfere with the measurement, and a filter membrane should be used to remove it during sampling.

5.2 The interference of acetate ions on fluoride determination can be eliminated and reduced by adjusting the concentration and flow rate of the eluent, replacing the chromatographic column, and other methods. six

Reagents and materials

Unless otherwise specified, analytical reagents that meet national standards are used for analysis, and fresh deionized water with a resistivity of ≥ 18 M Ω· cm is used for the experiment.

6.1 Potassium hydroxide (KOH): Superior grade purity.

6.2 Sodium Hydroxide (NaOH): Superior grade purity.

6.3 Sodium fluoride (NaF): High grade purity, dry at 110 ℃ for 2 hours before use, cool in a dryer for later use.

6.4 Alkaline absorption solution: c (KOH)=30 mmol/L or c (NaOH)=30 mmol/L. Weigh 1.68 g of potassium hydroxide (6.1) or 1.20 g of sodium hydroxide (6.2), dissolve in an appropriate amount of water, transfer to a 1000 ml volumetric flask, dilute with water to volume, mix well, and transfer to a polyethylene bottle. Ready to use and ready to use.

6.5 Rinse storage solution: Prepare according to the instrument model and chromatographic column instructions and usage conditions. Refrigerated and sealed below 4 ℃ can be stored for 3 months.

6.6 Rinsing solution: Dilute the rinsing stock solution (6.5) to obtain the rinsing solution, and prepare it immediately before use. Note 1: If the instrument model has the function of automatically generating shower solution online, it can be automatically generated. Note 2: The rinsing solution should be degassed before use to prevent bubbles from entering the ion chromatography system.

6.7 Fluoride storage solution: ρ (F -)=500 mg/L. Accurately weigh 0.1105 g of sodium fluoride (6.3) and dissolve it in an appropriate amount of water. Transfer it into a 100 ml volumetric flask, dilute with water to volume, mix well, and transfer it to a polyethylene bottle. It can be stored for one month at 4 ℃. Before use, take it out and store it at room temperature before use. Certified standard solutions can also be used for preparation.

6.8 Fluoride standard solution: ρ (F -)=50 mg/L. Take 10.00 ml of sodium fluoride stock solution (6.7), transfer it into a 100 ml volumetric flask, dilute with water to volume, mix well, and prepare immediately before use.

6.9 Filter membrane: made of polytetrafluoroethylene or quartz material, with a retention efficiency of not less than 99.9% for particles larger than 0.3 μ m.

7 Instruments and equipment

7.1 Constant temperature heating sampling tube: Install a filter membrane (6.9) at the end of the constant temperature heating sampling tube, with a heating temperature not lower than 120 ℃ and a temperature control accuracy of 1 ℃. The sampling tube is made of polytetrafluoroethylene or titanium alloy material, with a smooth and flowing inner surface. 7.2 Smoke Sampler The smoke sampler shall comply with the technical requirements of HJ/T 47, with a sampling flow rate of 0.1 L/min to 2.0 L/min.