There are many types of dust in the production environment of the power and coal industries, mainly including silica dust, coal dust, boiler dust, asbestos dust,
Cement dust, welding fumes, etc., are characterized by a high content of free silica in the dust and a relatively high degree of dispersion of the dust, that is, mostly respirable dust, so it is more harmful to dust personnel.
According to the physical and chemical properties of productive dust, the concentration in the air, the amount entering the human body and the site of action, the hazards produced are also different, mainly including rhinitis, pharyngitis, tracheitis, bronchitis
and other respiratory diseases. The Chinese government and the power and coal industry departments attach great importance to dust prevention work. Therefore, it is very important to strengthen the detection of free silica content in dust.
Wanted and urgent work. In the past, the content of free silica in dust was detected by the "pyrophosphoric acid gravimetric method" stipulated in "Determination of Dust in Workplace Air" (GB5748-85).
This method has a series of problems such as complex operation steps, various reagents used, long detection period, poor accuracy, and harsh laboratory conditions, which are difficult to meet the requirements of on-site batch detection.
Require. In order to improve the accuracy of detection and achieve the purpose of batch detection, ZFC-2000D Free Silica Analyzer in Dust is specially developed to detect free silica in dust
In order to meet the needs of different customers, ZFC-3000D free silica analyzer in dust has also been launched (using the original imported host). The imported type has high precision, faster speed,
The software function is more powerful and so on.
National Occupational Health Standards of the People's Republic of China
Determination of dust in workplace air
Part 4: Free silica content
Method for determination of dust in the air of workplace
Part 4: Content of free silica in dust
Published on June 18, 2007 Implemented on December 30, 2007
Published by the Ministry of Health of the People's Republic of China
GBZ/T 192 is divided into the following five parts according to the characteristics of dust determination in workplace air:
- Part 1: Total dust concentration
- Part 2: Respirable dust concentrations
- Part 3: Dust dispersion
- Part 4: Free silica content
- Part 5: Asbestos fibre concentration
This part is the fourth part of GBZ/T192, which is in GB 5748-85 "Determination method of dust in workplace air", GB16225-1996 "Hygienic standard for respirable silica dust in workshop air"
"Appendix B "Dust Free Silica X-ray Diffraction Determination Method", GB16245-1996 "Hygienic Standard for Respirable Coal Dust at Workplace" Appendix B "Free Silica Red in Respirable Coal Dust"
It was revised on the basis of "External Spectrometry".
This part is proposed by the National Occupational Health Standards Committee.
This part is approved by the Ministry of Health of the People's Republic of China.
This section is drafted by: School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan Iron and Steel Company Industrial Hygiene Technology Research Institute, Dongfeng Motor Corporation Occupational Disease Prevention Research Institute, Wuhan City
Occupational Disease Prevention and Control Research Institute, Hubei Provincial Center for Disease Control and Prevention, Fujian Provincial Center for Disease Control and Prevention, Liaoning Provincial Center for Disease Control and Prevention, Wuhan Analytical Instrument Factory.
The main drafters of this section: Yang Lei, Chen Weihong, Liu Zhanyuan, Chen Jingqiong, Li Jichao, Yi Guilin, Yang Jingbo, Mei Yong, Peng Kailiang, Liu Jiafa, Ye Bingjie.
Determination of dust in workplace air
Part 4: Free silica content
This part specifies the method for the determination of free silica content in workplace dust.
This section applies to the determination of free silica content in workplace dust.
2 Normative references
The clauses in the following documents, through reference in this standard, become clauses of this standard. For dated references, all subsequent amendments (excluding errata content) or revisions
are not applicable to this standard, however, parties to agreements based on this standard are encouraged to investigate the availability of the latest versions of these documents. For undated references, the latest edition is applicable.
used in this standard.
GBZ 159 Specification for monitoring and sampling of hazardous substances in the workplace air
GBZ/T XXX.1 Determination of Dust in Workplace Air Part 1: Total Dust Concentration
GBZ/T XXX.2 Determination of Dust in Workplace Air Part 2: Respirable Dust Concentration
3 Terms and Definitions
This section uses the following terms:
Refers to crystalline silica, that is, quartz.
5 Infrared spectrophotometry
α-Quartz has strong specific absorption bands at 12.5μm (800cm-1), 12.8μm (780cm-1) and 14.4 (694cm-1) μm in the infrared spectrum, within a certain range,
Its absorbance value has a linear relationship with the mass of α-quartz. Quantitative determination is performed by measuring absorbance.
5.2.1 Porcelain crucibles and crucible tongs.
5.2.2 Box-type resistance furnace or low-temperature ashing furnace.
5.2.3 Analytical balance with a sense of 0.1 mg.
5.2.4 Drying oven and dryer.
5.2.5 Agate Mortar.
5.2.6 Tablet press and tablet die.
5.2.7 200 mesh dust sieve.
5.2.8 Infrared spectrophotometer. Record the spectrum from 900cm-1 to 600cm-1 on the abscissa of the X-axis, correct zero and 100% at 900cm-1, and represent the absorbance on the ordinate of the Y-axis.
5.3.1 Potassium bromide, excellent grade or spectral purity, after passing through a 200-mesh sieve, ground with wet method, dried at 150°C, and stored in a desiccator for later use.
5.3.2 Anhydrous ethanol, analytical grade.
5.3.3 Standard α-quartz dust, the purity is above 99%, and the particle size is less than 5μm.
5.4 Collection of samples
According to the purpose of the measurement, see GBZ 159 and GBZ/T XXX.2 or GBZ/T XXX.1 for the method of sample collection. When the amount of dust collected on the filter membrane is greater than 0.1 mg, it can be directly used for the determination of the sample by this method.
from the silica content.
5.5.1 Sample processing: Accurately weigh the mass (G) of dust on the filter membrane with dust. Then fold the dust-receiving side inward 3 times, put it in a porcelain crucible, and place it in a low-temperature ashing furnace or resistance furnace
(less than 600 ℃), ashing, after cooling, put it in a desiccator for use. Weigh 250 mg of potassium bromide and the dust sample after ashing into the agate mortar, grind and mix, together with the tableting mold.
Put them together in a drying oven (110℃±5℃) for 10min. The dried mixed sample was placed in a tableting mold, and the pressure was 25 MPa for 3 min, and the prepared tablet was used as the measurement sample.
At the same time, a blank filter membrane was taken and treated in the same way as a blank control sample.
5.5.2 Drawing of quartz standard curve: Accurately weigh standard α-quartz dust of different masses (0.01mg ~ 1.00mg), add 250mg potassium bromide respectively, and place it in an agate mortar to fully grind it evenly.
uniform, and make transparent tablets according to the above-mentioned sample preparation method. The standard quartz ingots of different quality are placed in the optical path of the sample chamber for scanning, with three positions of 800cm-1, 780cm-1 and 694cm-1
The absorbance value of the ordinate is the ordinate, and the quartz mass (mg) is the abscissa, and three standard curves of α-quartz with different wavelengths are drawn, and the regression equation of the standard curve is obtained. without interference
Generally, 800cm-1 standard curve is used for quantitative analysis.
5.5.3 Sample measurement: place the sample tablet and the blank control sample tablet respectively in the optical path of the sample chamber for scanning, record the absorbance value at 800cm-1 (or 694cm-1), and repeat the scanning measurement.
Determined 3 times, after subtracting the average absorbance value of the blank control sample from the average absorbance value of the measured sample, the mass (m) of free silica in the sample was obtained from the α-quartz standard curve.
5.5.4 Calculation Calculate the content of free silica in dust according to formula (3):
In the formula: SiO2(F)——content of free silica (α-quartz) in dust, %;
m——mass of free silica in the measured dust sample, mg;
G——mass of dust sample, mg.
5.6.1 The detected amount of α-quartz in this method is 0.01mg; the relative standard deviation (RSD) is 0.64%~1.41%. The average recoveries ranged from 96.0% to 99.8%.
5.6.2 The particle size of the dust has a certain influence on the measurement results. Therefore, the sample and the quartz dust used for making the standard curve should be fully ground, so that the particle size is less than 5μm, accounting for more than 95%, before the analysis can be carried out.
5.6.3 The ashing temperature has a certain influence on the quantitative results of coal mine dust samples. If the coal dust samples contain a large amount of kaolin, it will decompose when ashing is higher than 600 ℃, and it will cause interference around 800cm-1.
If the ashing temperature is less than 600 ℃, this interference band can be eliminated.
5.6.4 If the dust contains clay, mica, amphibole, feldspar and other components, which can cause interference around 800cm-1, the standard curve of 694cm-1 can be used for quantitative analysis.
5.6.5 In order to reduce the random error of measurement, the laboratory temperature should be controlled at 18℃~24℃, and the relative humidity should be less than 50%.
5.6.6 The analysis conditions for preparing the quartz standard curve samples should be exactly the same as those of the tested samples to reduce errors.