GB/T 15433-1995 Determination of fluoride in ambient air - Lime filter paper - Fluoride ion selective electrode method
Some standard content:
National Standard of the People's Republic of China
Determination of the fluoride in ambient air
Lime filter paper·fluorine ion selective electrode method
Ambient air-Determination of the fluoride--Method by Jime-paper sampling and fluorine iun-selective electrode analysis1 Subject content and applicable scope
1.1 Subject content
GB/T15433—1995
This standard specifies the lime filter paper sampling and fluorine iun-selective electrode method (abbreviated as 1.TP method) for the determination of fluoride in ambient air. 1.2 Scope of application
1.2.1 Application field
This method is applicable to the determination of the long-term half-mean concentration of fluoride in ambient air. 1.2.2 Determination limit
When the sampling period is one month, the lower limit of the method is (.18 dm·)2 Principle
The fluorides in the air (fluoride oxide, silicon tetrachloride, etc.) react with the calcium hydrofluoride on the filter paper and are fixed. After extraction with total ion intensity adjustment buffer, the fluoride content on the lime filter paper is determined by fluoride ion selective electrode method, which reflects the average pollution of fluorides in the air during the placement period.
3 Reagents
Unless otherwise specified, the reagents used in this standard are all pure reagents, and the water used is deionized. 3.1 Perfluoric acid: 72%.
3.2 Sodium hydroxide solution: c(Na0H)==2.5mol/L3. 3 Sodium hydroxide solution: c(NaOH)=5 mol/L3.4 Preparation of lime suspension: Weigh 56 g of calcium oxide, add 250 ml of water to digest, slowly add 250 ml of perchloric acid (3.1) under stirring, and heat until smoke is produced. After cooling, add 200 ml of water and heat to evaporate until smoke is produced. Repeat once. If there is a precipitate, filter it with a glass sand core bucket ((13). Under stirring, add 1000 ml of sodium hydroxide solution (3.2) to the obtained transparent filtrate to obtain a calcium hydroxide suspension. After settling for a while, pour out the supernatant and wash it with water repeatedly for 5 to 6 times. Finally, add water to 5000 ml, the concentration is about 1 mmol, and store it for use. Shake well when using.
3.5 Total ionization adjustment buffer (TISAB) Weigh 5 8.0R sodium chloride, 10.1g sodium citrate, measure 50mL of glacial acetic acid, add about 500mL of water, dissolve. Add sodium hydroxide solution (3.3 about 135mL, adjust the solution pH to 5.2, add water to make up to 1000ml. 3.6 Sodium fluoride standard solution: 1000/mL, weigh 0.2210g sodium fluoride (super pure reagent. Bake at 110℃ for 2h. Cool to room temperature in a desiccator), dissolve in water, transfer to a 100mL volumetric flask, and make up to the mark with water. In polyethylene bottle, this solution is fluorine standard stock solution, stored in refrigerator, taken out and put to room temperature before use, approved by National Environmental Protection Agency on March 25, 1995, implemented on August 1, 1995
CB/T15433-1995
3.6.1 Sodium nitride standard solution 1: 100.0μg/mL. Accurately pipette 10.00ml of sodium fluoride standard solution (3.6), transfer to 100mL volumetric flask, and dilute to the mark with water.
3.6.2 Sodium fluoride standard solution I: 50.0 g/mL. Accurately pipette 50.00 mL of sodium fluoride standard solution 1 (3.6.1) into a 100 mL volumetric flask and dilute to the mark with water.
3.6.3 Sodium fluoride standard solution II: 25.0 tg/mL. Accurately pipette 50.00 mL of sodium fluoride standard solution (3.6.2) into a 100 mL volumetric flask and dilute to the mark with water.
3.6.4 Sodium fluoride standard solution W: 10.0 μg/mL. Accurately pipette 10.00 ml of sodium fluoride standard solution T (3.6.1), transfer it into a 100 ml volumetric flask, and dilute to the mark with water.
3.6.5 Sodium fluoride standard solution V: 5.0 g/mL. Accurately pipette 50.00 ml of sodium fluoride standard solution V (3.6,4), transfer it into a 100 ml volumetric flask, and dilute to the mark with water.
3.6.6 Sodium fluoride standard solution V: 2.5 g/mL. Accurately pipette 50.00 ml of sodium fluoride standard solution ￥ (3.6.5). Transfer it into a 100 ml volumetric flask, and dilute to the mark with water.
Note that the above solutions (3.6.7-3.6.6) are all made in polyethylene plastic bottles. Prepare them before use. 4 Instruments and Materials wwW.bzxz.Net
4. 1 LTP Standard sampling device,
a, sample box: a flat-bottomed plastic box with an outer diameter of 13 cm, an inner diameter of 12.6 cm, and a height of 2.5 cm (excluding the cover). The box contains a plastic annular gasket (outer diameter 12.5cm, inner diameter 11.0cm) and a plastic welding rod (or spring) for fixing the filter paper. b. Rain cover, using a sugar porcelain basin with a basin mouth diameter of 30cm and a basin height of 9cm, and the bottom of the basin is welded with iron sheet. - A diameter of 13cm and a height of 3cm are used to install the sampling box (see the sampling device diagram). 4.2 Fluoride ion selective electrode:
a. Measuring fluoride ion concentration range: 101~10mol. b. Determination of the slope of the curve: at t, it is (51+0.2t)m. 4.3 Glycerol electrode: The salt bridge liquid is saturated potassium chloride, 4.4 Small ultrasonic cleaner.
4.5 Fuel stirrer: Its polyethylene-wrapped environment stirrer, 4.6 Ion activity induction or precision acidity meter: The graduation value is less than 0.mV4.7 Polyethylene plastic cup: 100 m.5
1 Side view of rain cover
CB/T15433
Figure 2 Top view of rain cover
1--The iron ring of sampling box embedded in the bottom of rain cover is 2
Figure 3 Plastic pressing ring
Figure 1 Kazan (spring expansion ring)
Figure 5 Sectional view of assembled sampling box
1--Plastic box bottom: 2 Filter paper: 3-Plastic pressing ring for fixing filter paper: 4 Spring expansion ring for fixing plastic K ring-Kazan nail 6-Plastic box cover
4.8 Polyethylene plastic bottle: 100mL, 1000ml.4.9 Lime filter paper: Use two large culture media (about 15cm in diameter) and put a small amount of lime suspension in each. Put the 12.5cm diameter qualitative filter paper into the first culture media to soak and drain, and then put it into the second culture media to soak and drain (after soaking 5 to 6 filter papers, replace with new lime suspension), then spread it on a piece of qualitative filter paper (clean, fluorine-free), dry it at 60 to 70 degrees, put it in a plastic box (bag), seal it well and put it in a desiccator for standby use (no desiccant is added to the desiccator) 4.10 Qualitative filter paper 12.5cm
5 Sampling
GB/T 15433--1995
Take a piece of lime filter paper, lay it flat on the bottom of the flat plastic sampling box, press the edge of the filter paper with a ring-shaped plastic clamp, and then use an elastic plastic welding rod or a clamp spring to press along the edge of the box (rivets can be installed on the box to clamp the welding rod), fix the filter paper firmly, cover it, and carry it to the sampling point. The distance between sampling points is generally about 1k1. When it is close to the pollution source, the distance between sampling points can be reduced; the distance between sampling points far away from the pollution source can be increased. The sampling point should be set in a relatively open place, avoiding local small Pollution sources (such as smoke, etc.), the sampling device can be fixed on a pole or sampling rack 3.5~4m above the ground. In places with dense buildings, it can be installed on the roof, and the relative height to the foundation surface should be greater than 1.5m. When sampling, remove the lid of the sampling box with lime filter paper, put it into the iron ring at the bottom of the sampling rain cover, fix it, make the lime filter paper face down, and expose it to the air. The sampling time is 7 days to one month. Make good sample records [record the sample placement location, sample number and placement and sampling time (month, hour)}. When collecting samples, remove the sampling box. If the lid is sealed, take it back to the laboratory and store it in an empty desiccator. Complete the analysis within six weeks.
6 Analysis steps
6. Drawing of the calibration curve
Take 6 100mL polyethylene plastic cups + prepare the standard series according to Table 1, or prepare it according to the concentration of the sample to be tested, and no less than 6 points (take six standard dilutions of equal volume respectively). Connect the ion activity meter, and place the cleaned oxygen ion selective electrode and argon ion selective electrode into the prepared standard series solution as required. Measure from low liquid concentration to high concentration one by one, stir on the magnetic stirrer for several minutes, stop stirring after the reading is stable (i.e. the electrode potential change is less than 0.2 mV per minute), read the milliohm value after standing, and record the temperature during the measurement. On the semi-logarithmic coordinate paper, use logarithmic coordinates to represent the fluorine concentration; use equidistant coordinates to represent the millivolt value, and draw a calibration curve. Or make a linear regression. Obtain the regression equation, requiring 7>0.999 or above, and the slope is (54-0.21) mV. The calibration curve should be drawn at the same time as the sample is measured. Table 1 Standard solution preparation series
F standard solution. μg/ml.
Take standard solution, ml
TIS4B dissolved 2, mL
F-content, Ag
6.2 Sample determination
Take out the lime filter paper sample, cut it into small pieces (about 5×5 mm): put it in a 100mL polyethylene plastic cup, add 25.00mL TISA buffer and 25.00mL water. The total volume is 50. 00 mL, and extract it in a sonicator for 30 tminl, take out and place overnight (if covered, prevent contamination during placement). According to the calibration curve determination method, after reading the optimal value, check the fluorine content from the calibration curve or calculate the fluorine content according to the indirect equation. The temperature difference between the sample determination and the calibration curve drawing should not exceed ±2°C. 6.3 Blank value determination
, extract 45 unsampled lime filter papers and determine them by the standard addition method, that is, add 0.5 mL of sodium fluoride standard dilution (10 /mL) to the shredded blank lime filter paper, and then determine its combined amount according to the sample determination method. The total volume of the determination solution is 50.00 mT. Take the average value as the fluorine content of the blank lime filter paper (the fluorine content of each blank lime filter paper should not exceed 1μg). The fluorine content of the blank lime filter paper is the measured value () minus the added standard fluorine content (5). 7 Interference removal
GB/T 15433--1995
When Si4, Fe\\Al\\ exist in the determination system (the upper limit of its concentration is 20ppm), the interference can be eliminated by adding total ion intensity adjustment flushing liquid.
8Calculation of analysis results
C(Fμg/dm.d)
W—fluoride concentration in ambient air/dm·d; W—fluoride content in the right lime filter paper sample·
W. A blank lime filter paper average fluoride content, ug: S-…: The area of the sample filter paper exposed to the air, dmn: The number of days the sample filter paper is placed in the air, accurate to 0.1d. 9Precision and accuracy|| tt||9.1 Precision
Five laboratories collected parallel samples at different locations, 5 samples in each group: a total of 31 groups of samples were obtained, the mean range of the determination was 2.81～192ug/(dm.d), the average coefficient of variation was 5.5% and the maximum was 16.6%. 9.2 Accuracy
Five laboratories determined the uniformly prepared fluorine-containing 50.0g lime filter paper standard sample, and the relative error was 0.23%. Additional remarks:
This standard was proposed by the Standard Division of the Science and Technology Standards Department of the State Environmental Protection Administration, and the Baotou Environmental Monitoring Station was responsible for drafting this standard. The main drafters of this standard were Wu Xiaping and Xu Xinmin. This standard is interpreted by the China National Environmental Monitoring Center.
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