GB 16229-1996 Hygienic standard for tungsten in workshop air

This standard specifies the maximum permissible concentration of tungsten in workshop air and its monitoring and inspection methods. This standard is applicable to all types of enterprises that produce and use tungsten. GB 16229-1996 Hygienic Standard for Tungsten in Workshop Air GB16229-1996 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Health standard for tungsten in the air of workplace
Health standard for tungsten in the air of workplace Subject content and scope of application
This standard specifies the maximum allowable concentration of tungsten in the air of workplace and its monitoring and inspection methods. This standard applies to all types of enterprises that produce and use tungsten. 2 Hygiene requirements
The maximum allowable concentration of tungsten in the air of workplace is 6mg/m3. 3 Monitoring and inspection methods
GB16229—1996
The monitoring and inspection method of this standard adopts the potassium thiocyanate-titanium trifluoride spectrophotometric determination method, see Appendix A (supplement). 4 Supervision and implementation
Health and epidemic prevention agencies at all levels are responsible for supervising the implementation of this standard. Approved by the State Administration of Technical Supervision on April 3, 1996, and implemented on September 1, 1996
A1 Principle
GB16229—1996
Appendix A
Spectrophotometric determination method of tungsten in workshop air by potassium thiocyanate-titanium trifluoride (supplement)
The tungsten in the air is collected on a microporous filter membrane. After the filter membrane sample is digested by acid, the tungsten reacts with potassium thiocyanate under the action of a reducing agent to form a yellow complex.
A2 InstrumentswwW.bzxz.Net
A2.1 Dust sampler.
A2.2 Standard filter membrane sampling clamp.
A2.3 Filter material: microporous filter membrane, pore size 0.8um, diameter 45mm. A2.4100mL volumetric flask.
A2.550ml. Erlenmeyer flask.
A2.625mL stoppered colorimetric tube.
A2.720mm colorimetric cup.
A2.8721 spectrophotometer.
A3 Reagents
The general reagents used in this method are all analytically pure, and the reference reagents are analytically pure. A3.1 The experimental water is all glass distilled water or deionized water, with a resistance of more than 1000k2. A3.21+9 perchloric acid-nitric acid solution.
A3.3 Mixed acid: Pour 100mL sulfuric acid carefully into 500mL water, add 300mL phosphoric acid after cooling, and dilute with water to 1000ml.
A3.40.5% (5g/L) stannous chloride solution: Weigh 0.5g stannous chloride and dissolve it in 100mL 1:1 hydrochloric acid. A3.525% (250g/L) potassium thiocyanate solution. A3.61% titanium trichloride solution: Take 2.5mL 15% (150g/L) titanium trichloride in a 25mL volumetric flask, dilute to scale with 1:3 hydrochloric acid, and prepare before use.
A3.7 Standard solution: Weigh 1.7936g sodium tungstate (NazWO,·2H,O) and dissolve it in a small amount of water, and transfer it into a 1000mL volumetric flask, dilute to scale with water, 1mL of this solution = 1mg tungsten.
A4 Sampling
Install the microporous filter membrane in the sampling clip of the dust sampler, and collect 50L of air sample at a speed of 5L/min. A5 Analysis steps
A5.1 Control test: Bring the microporous filter membrane to the site without sampling, and perform the same analysis as a control and quality control. A5.2 Sample treatment: Place the sampled microporous filter membrane in a 50mL conical flask, add 2mL of 1+9 perchloric acid-nitric acid mixed digestion solution, place on an electric stove for heating and digestion, remove the filter membrane after it is digested (light brown), add 20mL of mixed acid, continue heating and digestion until white smoke appears and the digestion solution is colorless and transparent, remove and cool, transfer to a 100mL volumetric flask, wash the conical flask with water, pour the washing solution into the volumetric flask, dilute to the scale and shake well, take 10mL into a 25mL colorimetric tube. A5.3 Drawing of standard curve: Take 6 50mL conical flasks and prepare standard tubes according to Table A1. 524
Standard solution, mL
Microporous filter membrane, Zhang
Tungsten content, ug
GB16229
9—1996
Preparation of standard tube
After sample treatment, make up to 100mL. Take 10mL in a 25mL colorimetric tube, add 5mL stannous chloride solution, 2mL potassium thionitric acid solution, and 0.5mL titanium trichloride solution to each tube, shake well, use a 20mm colorimetric cup for colorimetric analysis at a wavelength of 400nm, and draw a standard curve.
A5.4 Determination: The operation of the sample tube is the same as that of the standard tube. After colorimetric analysis, the tungsten content is found from the standard curve. A6 Calculation
Calculate the concentration of tungsten in the air according to formula (A1): x=.
Where: X--tungsten concentration in air, mg/m; C--tungsten content in sample solution, μg; V. --converted to sampling volume under standard conditions, L. A7 Description
A7.1 The detection limit of this method is 3μg/10mL.
A7.2 Under the experimental conditions of this method, when the tungsten concentration is 20.60 and 100μg/10mL, the coefficient of variation is 3.36%, 2.29% and 1.27% respectively.
A7.3 The sampling efficiency of this method is 94% to 100%. During the sampling process, pollution should be prevented. Filter membranes should not be installed at high-concentration tungsten production sites. Sampling tools such as sampling clips and tweezers should be kept clean. In addition, the sampling weight increase generally does not exceed 20mg to prevent dust from falling during sampling, storage and transportation.
A7.4 The degree of complete sample digestion is best when the white smoke is separated from the solution surface. If the white smoke is not separated from the solution surface, the digestion may be incomplete. If white precipitate appears in the sample after digestion, it must be clarified or centrifuged to obtain the supernatant, which will not affect the determination. A7.5 Under the conditions of this test, 200μg of molybdenum and iron, 100μg of cobalt, cadmium, copper, nickel, and 50μg of manganese and zinc have no interference with the determination of 20μg of tungsten.
Additional instructions:
This standard was proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Shenyang Institute of Labor Hygiene and Occupational Diseases and the Jiangxi Institute of Labor Hygiene and Occupational Disease Prevention and Control. The main drafters of this standard are Yang Meiyu, Yang Shuangcai, and Zhang Tianyuan. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, the technical management unit entrusted by the Ministry of Health. 525
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