Some standard content:
National Standard of the People's Republic of China
Health standard for tin dioxide in the air of workplace
Subject content and scope of application
This standard specifies the maximum allowable concentration of tin dioxide in the air of workplace and its monitoring and inspection methods. This standard is applicable to all types of enterprises that produce and use tin dioxide. Hygienic requirements
The maximum allowable concentration of tin dioxide in the air of workplace is 2mg/m2 (calculated as tin). 3 Monitoring and inspection methods
The monitoring and inspection methods of this standard adopt spectrophotometry, see Appendix A (supplement). Approved by the State Administration of Technical Supervision on April 3, 1996 476
GB16216—1996
Implementation on September 1, 1996
A1 Principle
GB16216—1996
Appendix A
Spectrophotometry
(Supplement)
Under acidic conditions and in the presence of thiourea, tin and quercetin form a yellow complex, which is quantitatively determined by colorimetry. A2 Apparatus
A2.1 Sampling clip.
A2.2 Filter material: vinyl peroxide filter membrane.
A2.3 Dust sampler.
A2.4 Iron crucible, 30mL.
A2.5 Stoppered colorimetric tube, 10mL, 25ml. A2.6 High-temperature electric furnace.
A2.7 Spectrophotometer.
A3 Reagents
A3.1 Quercetin ethanol solution, 1g/L. A3.2 Thiourea solution, 50g/L.
A3.3 Hydrochloric acid c(HCl)=4mol/L.
A3.4 Hydrochloric acid, c(HCI)=1mol/L.
A3.5 Sodium hydroxide solution, c(NaOH)=10mol/L. A3.6 Sodium hydroxide solution, c(NaOH)=1.5mol/L. A3.7 Sodium hydroxide solution, c(NaOH)=1mol/L. A3.8 Standard solution: Accurately weigh 0.1000g of tin dioxide, place it in the treated iron (see A7.6), add 6mL of sodium hydroxide solution (A3.5), heat it in an electric furnace to remove moisture, transfer it to a 300℃ high-temperature electric furnace, heat it to 700℃ and keep it for 15min, take it out and let it cool, dissolve the melt in 80mL of boiling water in batches, boil the solution until the volume is reduced to half, filter it with double-layer slow quantitative filter paper into a 100mL volumetric flask, wash the pot and precipitate with 20mL of boiling water, add 30mL of concentrated hydrochloric acid to the filtrate, let it cool, and add water to the scale. This solution is the stock solution, 1mL=1mgSnO2.
Standard application solution: Take 2ml of standard stock solution, add hydrochloric acid (A3.4) to dilute it to 100mL, this solution 1mL=20μgSnOz. A4 Sampling
Fix the filter membrane in the sampling clip and extract 50~~100L of air at a speed of 5~10L/min. A5 Analysis Steps
A5.1 Control test: Use the unsampled filter membrane (A2.2) according to the sample processing steps as a blank control. A5.2 Sample processing: Place the sampled filter membrane in the treated iron crucible, add 1.5mL of sodium hydroxide solution (A3.5) after carbonization, and proceed as follows according to the standard solution preparation steps. Boil the melt with 8mL of water to dissolve, filter with slow quantitative filter paper, wash the crucible and precipitate with 2mL of boiling water, cool, add water to 10mL, and mix well. A5.3 Drawing of standard curve: Take 6 10mL colorimetric tubes and prepare standard tubes according to Table A1. 477
Standard solution, ml
Hydrochloric acid (A3.4), mL
Sodium hydroxide solution (A3.7), ml
Sn(), containing base, ug
GB16216-1996
Preparation of tin dioxide standard tube
Add 2mL thiourea solution (A3.2) and 2mL 95% (V/V) ethanol to each tube and mix well. Add 1.0mL quercetin solution (A3.1), shake and mix well, let stand for 15min, colorimetric at a wavelength of 440nm, plot the tin dioxide content against the absorbance, and draw a standard curve. A5.4 Determination: Take 1mL of the sample solution (A5.2) (if the concentration is high, dilute it with sodium hydroxide solution (A3.6)) in a 10mL colorimetric tube, add 0.5ml. hydrochloric acid (A3.3), and analyze according to the standard series operation steps below. After the absorbance value of the sample is subtracted from the absorbance value of the blank control, the tin dioxide content is found from the standard curve. A6 CalculationbzxZ.net
Where: X-
SnO2 concentration in the air, mg/m3;
-SnO2 content in the sample, ug;
V,-Sample volume under standard conditions, L. A7 Explanation
A7.1 The detection limit of this method is 0.8ug/6.5mL, and the measurement range is 0-20μg. When the tin dioxide content is 1.0, 5.0, 10.0, 15.0 and 20.0μg/6.5mL, the coefficient of variation is 6.7%, 4.1%, 2.0%, 1.8% and 2.0% respectively. A7.2 The perchloroethylene filter membrane has low resistance and high retention efficiency. The average sampling efficiency of tin dioxide is 96.9%. A7.3 Tin dioxide samples are stable and do not require special storage. After the sampling filter material is folded in half, it can be carried and transported by wrapping it in clean paper. A7.4 The appropriate acidity for the reaction between quercetin and tin is 0.01-0.1 mol/L hydrochloric acid. If the acidity increases, the absorbance value of the solution will decrease, affecting the determination. In terms of reagent dosage, the amount of quercetin solution (A3.1) added is preferably 1.0-2.0 mL; when the amount of sulfur gland solution (A3.2) added is 0-2.5 mlL, it has no effect on the color reaction. A7.5 Under the determination conditions, 50 times of K+, Nat, Co2+, Fe3+, Fe2+, Ge4+, Ba2+, Hg2+, CIO, SO2-, NO:, C1-, Br and 1-; 10 times of Mg2+, Zn2+, Cu2+Mn2+, Ca2+; 30 times of F-; 8 times of Pb2+ and As3+; 7 times of Cr3+ and 5 times of SiO (added to sample for treatment) have no effect on the determination. 1 times of Sb2+ has a slight effect on the determination, but the content of Sb2+ in the air dust elements is less than 0.5% (m/m) of the tin content.
A7.6 Burn the new iron, remove the oil and then wash it, soak it in 1+3 hydrochloric acid to remove rust, then soak it in 5% (V/V) concentrated nitric acid and 5% (V/V) concentrated sulfuric acid (mixed solution of equal volume) for 5 minutes, then wash and dry it, and purify it at 700C for 5-10 minutes. Additional remarks:
This standard was proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Sichuan Provincial Institute of Labor Hygiene and Occupational Disease Prevention and Control. The main drafters of this standard were Wang Dingguo, Liu Jingdong, and Wu Zengshu. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, the technical unit entrusted by the Ministry of Health. 478
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