This standard specifies the method for determining the concentration of molybdenum and its compounds in the air of workshops by thiocyanate spectrophotometry. This standard is applicable to the determination of the concentration of molybdenum and its compounds in the air of workshops that produce and use molybdenum and its compounds. GB/T 16103-1995 Method for the determination of molybdenum and its compounds in the air of workshops by thiocyanate spectrophotometry GB/T16103-1995 Standard download decompression password: www.bzxz.net

GB/T16103—1995
This standard is a monitoring method supporting the labor hygiene standard, used to monitor the concentration of molybdenum and its compounds in the workshop air. This standard is proposed after laboratory research and field verification with reference to foreign monitoring methods and in combination with the situation in my country. This standard will be implemented from July 1996. This standard is proposed by the Ministry of Health of the People's Republic of China. The drafting units of this standard are: Shaanxi Provincial Health and Epidemic Prevention Station, Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine. The main drafters of this standard are: Xu Fangli and Xu Bohong. This standard is entrusted by the Ministry of Health to the technical unit, Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, to interpret it. 1 Scope
National Standard of the People's Republic of China
Spectrophotometric Determination of Molybdenum and Its Compounds in Workplace Air
Spectrophotometric Determination of Thiocyanate and Its Compounds-Thiocyanate Spectrophotometric Method GB/T 16103—1995
This standard specifies the method for determining the concentration of molybdenum and its compounds in the air of workshops by thiocyanate spectrophotometry. This standard is applicable to the determination of the concentration of molybdenum and its compounds in the air of workshops that produce and use molybdenum and its compounds. 2 Principle
In the presence of reducing agents and copper ions in an acidic solution, molybdenum and thiocyanate rapidly generate a stable orange-red complex, which is quantitatively measured by colorimetry. 3 Apparatus
3.1 Sample clamp,
3.2 ethylene filter membrane or microporous filter membrane,
3.3 Sampler.
3.4 ​​Stoppered colorimetric tube. 25mL
3.5 Spectrophotometer,
4 Reagents
4.1 Potassium thiocyanate solution, 250g/l.
4.2 Ascorbic acid solution, 50g/L,
4.3 Copper sulfate solution, 0.4g/L. www.bzxz.net
4.4 Sulfuric acid solution. 1—2.
4.5 Sulfuric acid Acid solution, 1 + 9.
4.6 Sulfuric acid solution. 11·4.
4.7 Nitric acid solution. 3+5
4.8 Mixed color developer: Mix 100mL each of potassium thiocyanate solution, ascorbic acid solution, and sulfuric acid solution (4.4) with 5mL of copper sulfate solution and prepare on the same day
4.9 Standard solution: Weigh 0.2522g of sodium molybdate (VazMo0,·2H,0). Dissolve in a small amount of water and transfer to a 100nl volumetric flask. Add 2mL sulfuric acid solution (4.4) and water to the cracking point. This solution is 1.0mg/ml aluminum. Dilute with sulfuric acid solution (4.5) to a 10μg/mL standard solution before use.
5 Sampling
Place the filter membrane in the sampling clamp and clamp it. Draw 100L of air at a flow rate of 101./min. Approved by the State Administration of Technical Supervision on December 15, 1995 and implemented on July 1, 1996
6 Analysis steps
GB/T 16103—1995
6.1 Control test Bring the sampling clamp with the filter membrane to the sampling point. Except for not collecting air, the rest of the operation is the same as the sample, which serves as the empty control of the sample.
6.2 Sample treatment Place the sampled filter membrane in a 50mL beaker. Add 5mL sulfuric acid solution (4.6) and 0.4ml nitric acid solution, shake well, and slowly heat. When the solution starts to emit white smoke, remove and cool. Transfer quantitatively into a 50mL volumetric flask with water. Add 4mL sulfuric acid solution (1.6), dilute to the scale with water, and shake. Measure 5ml and place in a colorimetric tube for analysis. 6.3 Drawing of standard curve Prepare standard tubes according to Table 1. Table 1 Preparation of molybdenum standard tubes
Standard solution + mL
sulfuric acid solution (4.5), mL
platinum content
Add 6ml to each tube. Mix the colorimetric agent and shake. Let stand for 10 minutes and measure the absorbance at a wavelength of 470nm. Plot the absorbance against the content (ug) to draw a standard curve.
6.4 The sample tube is measured in the same way as the standard tube, and the clamp content (μg) is obtained from the standard curve. 7 Calculation
7.1 According to formula (1), convert the sampling volume into the volume under standard conditions. V. - ×
Where: V-
The sample volume under standard conditions, L:
-Sample volume, L;
p——Air pressure, kPa:
Air temperature, T.
7.2 According to formula (2), calculate the concentration of aluminum,
The concentration of aluminum in the air, mg/m
The clamp content g obtained from the standard curve:
V,—The deep sample volume under standard conditions. L., 8 Notes
8.1 The detection limit of this method is 1g/5ml. When the concentration of tin is 5.0.10.20.30.50μg/5ml, the relative standard deviation is 1.7%, 2.5%, 2.5%, 2.8% and 1.7% respectively. 8.2 The sampling efficiency of this method is 96.8%, and the elution efficiency is 95.7%. 8.3 When heating and dissolving the tin on the filter membrane, the temperature should not be raised too quickly and the temperature should not be too high to prevent the filter membrane from carbonizing and turning black, which will affect the determination. 8.4 The mixed color developer is best prepared in large quantities,
8.5 1000μg of tungsten (M), silicon (N) and lead, 100g of iron (), chromium (M), vanadium (V) and cobalt (I) have no interference with this method.
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