This standard specifies the method for determining the concentration of iodomethane in workshop air by spectrophotometry using sodium 1,2-naphthoquinone-4-sulfonate. This standard is applicable to the determination of iodomethane concentration in workshop air where iodomethane is produced and used. GB/T 16123-1995 Method for determining iodomethane in workshop air by spectrophotometry using sodium 1,2-naphthoquinone-4-sulfonate GB/T16123-1995 Standard download decompression password: www.bzxz.net

GB/T 16123—1995
This standard is a monitoring method for labor hygiene standards, used to monitor the concentration of methyl iodide in the air of workshops. 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 is effective from July 1996.
This standard is proposed by the Ministry of Health of the People's Republic of China. The drafting unit of this standard: 1. Shanghai Municipal Health and Epidemic Prevention Station. The main drafters of this standard: Yan Huai Zeng, Wen Yi Min, Shuai Ke Jun. The Ministry of Health entrusted the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, to interpret this standard. National Standard of the People's Republic of China
Determination of methyl iodide-1,2-paphtbaquinone4-sodium sulfonate spectrophutumeiric method in workplace air
Workplace airDetermination of methyl iodide-1,2-paphtbaquinone4-sodium sulfonate spectrophutumeiric methodScope
GB/T 16123
This standard specifies the method for determining the concentration of methyl iodide in workplace air by the spectrophotometric method of 1,2-paphtbaquinone-4-sodium sulfonate. This standard is applicable to the determination of the concentration of iodine in the workplace air where iodine is produced and used2Principle
Methyl iodide reacts with sodium nitrite to generate nitromethane, which reacts with sodium 1,2-naphthaldehyde-4-sulfonate in the presence of sodium hydroxide to generate a purple-blue compound, which is quantitatively measured by colorimetry.
3Instrument
3.1Porous glass plate absorption tube.
3.2Vacuum pump.
3.3 Flow meter, 0 L/min~1 L/mi,
3.4 ​​Other stopper tube, 10 ml.a
3.5 Spectrophotometer, 10mm colorimetric cup.
4 Reagents
Absorption liquid: anhydrous 2. alcohol.
4.2 1,2-naphthaldehyde-4-sulfonic acid sodium solution: prepare before use, 3g/L. 4.3 Sodium nitrite solution: 350g/1..
4.4 Sodium hydroxide solution: 0.035mol/L
4.5 Standard solution: add 10ml absorption liquid to a 25ml base bottle, weigh accurately, add 3 drops of iodomethane, weigh accurately again, the difference between the two weighings is the mass of iodomethane. Add absorption liquid to the scale and calculate the content of methyl iodide in 1m solution. When using, dilute with absorption liquid to a standard solution of 1ml_=100g methyl iodide.
5 Sampling
Connect two porous glass plate absorption tubes each containing 10ml absorption liquid in series, and extract 20I of air at a rate of 0.5L/min. 6 Analysis steps
6.1 Control test
Same as sampling. Bring the absorption tubes filled with absorption liquid to the site, but do not extract air, and analyze according to the sample. Approved by the State Administration of Technical Supervision on December 15, 1995 and implemented on July 1, 1996
6.2 Sample treatment
GB/T 16123—1995
After sampling, wash the inner wall of the air inlet pipe 3 times with the absorption liquid in the absorption tube. Take 5.0ml of sample solution from each absorption tube and put it into a colorimetric tube for determination.
6.3 Prepare standard tubes with 10mL colorimetric tubes according to Table 1 Table 1
Preparation of iodine methyl standard tubes
Standard solution, nl.
Residue mL
Iodine methyl plate·
Add 0.1mL 1,2-dihydrogen nitrate-4-sodium solution to each standard tube, stir well, add 0.2mL sodium nitrite, shake, heat in a 80°C water bath for 20min, take out and cool, add 0.1mL sodium hydroxide solution, shake 1mil, colorimetric at a wavelength of 579nm, plot the iodine methyl content () against the absorbance, and draw a standard curve. 6.4 Determination
According to the same operating conditions as in 6.3, the treated sample is measured, and the content of iodine methyl (μg) is found from the standard curve. 7 Calculation
7.1 Convert the sample volume into the volume under standard conditions according to formula (1). V.-X
Wherein: V. —— Sample volume under standard conditions, L; V— Sample volume,;
Temperature,;
p— Atmospheric pressure, kPa.
7.2 Calculate the degree of iodine in alkyl according to formula (2).
2(mi +m2)
Where:—
-Concentration of iodomethane in the air, mg/m~;
Content of iodomethane in the sample taken from the first absorption tube, :m
Content of iodomethane in the sample taken from the second absorption tube, Vn--Converted to the sampling volume under standard conditions, L, 8 NotesbZxz.net
8.1 The detection limit of this method is 3μg/5mL. When the content of iodomethane in iodine is 10, 20, 40, 60.80 μg/5mL, the coefficient of variation is 11.6%, 10.4%, 7.1%, 6.5%, 5.1% respectively. 8.2 The sample should be analyzed on the same day as far as possible. If not possible, it can be placed in the refrigerator for no more than one week. 8.3 Because of the mixing when adding saturated calcium hydroxide solution, this method uses 0.035mnl/1. sodium hydroxide solution instead.
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