HJ 481-2009Ambient air. Determination of the fluoride. Lime-paper sampling followed by fluorine ion-selective electrode method (English PDF)

Foreword

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 Atmospheric Pollution Human health, standardizing the monitoring methods for fluoride in the air, and developing this standard.

This standard specifies a sample of fluoride ion-selective electrode for the determination of fluoride in the ambient air.

This standard is for the determination of fluoride in ambient air, lime filter paper and fluoride ion selective electrode method (GB/T 15433-1995) Line revision.

This standard was first published in 1995. The original standard drafting unit was Baotou Environmental Monitoring Station. This is the first revision.

The main revisions are as follows.

-- modified the name of the standard;

- In the reagents and materials, the purity of the reagents used is specified, and the detailed preparation process of sodium hydroxide is added; the total ions are added.

Method for preparing intensity adjustment buffer; simplifying the preparation process of standard solution;

- specifies the operating conditions of the fluoride ion selective electrode;

-- Added electrode cleaning method to the precautions.

The national environmental protection standard "Environmental Environment" approved and issued by the former National Environmental Protection Agency on March 25, 1995, from the date of implementation of this standard.

Determination of air fluoride Lime filter paper · fluoride ion selective electrode method (GB/T 15433-1995) abolished.

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

This standard was drafted. Shenyang Environmental Monitoring Center Station.

This standard was approved by the Ministry of Environmental Protection on September 27, 2009.

This standard has been implemented since November 1, 2009.

This standard is explained by the Ministry of Environmental Protection.

Determination of ambient air fluoride Lime filter paper sampling fluoride ion selective electrode method

1 Scope of application

This standard specifies the fluoride ion selective electrode method (LTP method) for the determination of fluoride in the ambient air.

This standard applies to the determination of the long-term average pollution level of fluoride in ambient air.

When the sampling time is one month, the lower limit of the method is 0.18 µg/(dm2 · d).

2 Normative references

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

quasi.

GB 7484 Determination of fluoride in water quality - Ion selective electrode method

3 Principle of the method

Fluoride (hydrogen fluoride, silicon tetrafluoride, etc.) in the air is reacted with calcium hydroxide immersed in the filter paper to be fixed. Total ionic strength After adjusting the buffer leaching, the content of fluoride on the lime filter paper was determined by a fluoride ion selective electrode method. The measurement results reflect the placement the average level of fluoride in the air during the period.

4 Reagents and materials

The reagents used in this standard are analyzed using analytical reagents in accordance with national standards, unless otherwise stated.

Deionized water or distilled water.

4.1 Perchloric acid. 72%, excellent grade pure.

4.2 Sodium hydroxide solution c (NaOH) = 2.5 mol/L. Weigh 100.0 g of pure grade sodium hydroxide, dissolved in water, and then diluted to 1 000 ml after cooling.

4.3 Sodium hydroxide solution c (NaOH) = 5.0 mol/L. Weigh 100.0 g of excellent grade pure sodium hydroxide, dissolved in water, and then diluted to 500 ml after cooling.

4.4 Preparation of lime suspension. Weigh 56 g of calcium oxide, add 250 ml of water, slowly add perchloric acid (4.1) 250 ml with stirring, add Heat to produce white smoke. After cooling, add.200 ml of water and heat to evaporate until white fumes are produced. Repeat three times. If there is sediment, use glass sand core to leak.

Bucket (G3) filtration. To the resulting transparent filtrate, a sodium hydroxide solution (4.2) of 1 000 ml was added under stirring to obtain a calcium hydroxide suspension. Static After settling, the supernatant is decanted, and washed repeatedly 5 to 6 times with water. Finally, water is added to 5 000 ml, the mass fraction is about 1%, and it is kept in a sealed state.

Shake well when using.

5 Instruments and equipment

5.1 Sampling device.

a. Sample box. Flat-bottomed plastic case with an outer diameter of 130 mm, an inner diameter of 126 mm and a height of 25 mm (excluding the cover), with a cover. Inside the box Plastic ring gasket (outer diameter 125 mm, inner diameter 110 mm) and plastic welding rod (or spring ring) for fixing filter paper.

b. Rain cover. rain cover with a diameter of 300 mm and a height of 90 mm. The bottom of the basin is welded with a diameter of 130 mm and a height of 35 mm.

Circle for mounting the sample box.

The sampling device is shown in Figure 1. The dimensions in the figure are in mm.

Phi130 rain cover

Phi300

1-metal ring with fixed sampling box (130 mm diameter) a. rain cover side view b. rain cover bottom view Phi125 Thick 1~2 Phi110 Phi125 Thick 5~6 Phi125 1- plastic box bottom; 2-filter paper; 3- fixed filter paper plastic pressure ring;

4-spring clamp ring for fixing plastic pressure ring;

5-reed pin; 6-plastic cover c. plastic pressure ring d. circlip (spring up) e. assembled sample box profile

Figure 1 sampling device diagram

5.2 Ion activity meter or precision acidity meter. resolution is 0.1 mV.

5.3 Fluoride ion selective electrode.

(1) Measurement of fluoride ion concentration range. 10-5~10-1 mol/L.

(2) Determination of the slope of the curve. at t ° C, (54 0.2 t) mV.

5.4 Calomel electrode. The salt bridge solution is saturated potassium chloride.

5.5 Magnetic stirrer. with polyethylene wrap.

5.6 Small ultrasonic cleaner.

5.7 Polyethylene plastic cup. 100 ml.

5.8 Polyethylene plastic bottles. 100, 1 000 ml.

6 Interference and elimination

There are Si4, Fe3, and Al3 in the immersion liquid. When the mass concentration does not exceed 20 mg/L, the interference generated can be added to the total ion intensity.

Adjust the buffer to eliminate it.

7 Samples

Take a piece of lime filter paper, tiling it on the bottom of the flat-bottomed plastic sample box, press the filter paper edge with a ring-shaped plastic collar, and use elastic plastic the electrode or the circlip is pressed along the edge of the box (the rivet can be installed on the box to catch the electrode). Secure the filter paper firmly, cover it, and carry it to the sampling point.

The distance between sampling points is generally about 1 km. When the source is near, the distance between sampling points can be reduced, and the sampling point away from the pollution source.

The distance between them can be increased. Sampling points should be located in relatively empty areas, avoiding local small sources of pollution (such as chimneys, etc.). The sampling device can be fixed at on the sampling rack of 3.5~4 m on the ground; in the densely populated area, it can be installed on the roof, and the height relative to the base surface should be more than 1.5 m.

When sampling, remove the lid of the sample box containing the lime filter paper, put it into the bottom iron ring of the sampling rain cover, fix it, and make the lime filter.

The paper is facing down and exposed to the air for a period of 7 d to one month. Do a good sampling record [record the sample location, sample number and put Sample, sampling time (month, day, hour), etc.]. When taking the sample, take out the sample box from the rain cover, seal it, and bring it back to the lab.

The collected samples were stored in a laboratory air dryer and analyzed within 40 days.

8 Analysis steps

9 Results indicate

The content of fluoride in the air rho (F-) is calculated according to formula (1).

rho - -= × (1)

Where. rho (F-)--the content of fluoride in the air, µg/(dm2 · d);

W--the fluorine content of the lime filter paper sample measured according to 8.3, µg;

W0--the average fluorine content of the blank lime filter paper measured according to 8.2, µg;

S--the area of the sample filter paper exposed to the air, dm2;

n--The number of days in which the sample filter paper is placed in the air, d, should be accurate to 0.1 d.

The results are expressed in 3 significant digits.

10 Precision and accuracy

11 Precautions

Do not touch the surface of the electrode with a finger. To protect the electrode, the measured concentration of fluorine in the sample should not exceed 40 mg/L. If the electrode the surface of the membrane is contaminated with organic matter and must be cleaned before use. The organic reagents such as methanol and acetone may be used for washing, and detergents may also be used.

For example, the electrode can be immersed in a warm, dilute detergent (1 part detergent plus 9 parts water) for 3 to 5 minutes. Can be placed in another diluted detergent in. It was then rinsed with water, immersed in (1 1) hydrochloric acid for 30 s, and finally rinsed with water, and the water was removed by a filter paper.