This standard specifies the formaldehyde-pararosaniline spectrophotometric method for the determination of sulfur dioxide in ambient air. This standard applies to the determination of sulfur dioxide in ambient air. GB/T 15262-1994 Determination of sulfur dioxide in ambient air Formaldehyde absorption-pararosaniline spectrophotometric method GB/T15262-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Ambient air, determination of sulfur dioxide
Formaldehyde absorption-pararosaniline spectrophotometryAmbient air- Determinatlon of sulfur dioxideFarmaldehyde absorbing-pararosaniline spectrophotometry1 Subject content and scope of application
1.1 Subject content
This standard specifies the formaldehyde-pararosaniline spectrophotometry for the determination of sulfur dioxide in ambient air. 1.2 Scope of application
1.2.1 This standard applies to the determination of sulfur dioxide in ambient air. 1.2.2 Determination lower limit:
GB/T15262-94
When 10mL of absorption liquid is used to sample 301., the determination lower limit of this method is 0.007mg/m3. When 50ml of absorption liquid is used to sample 300L for 24h, the determination lower limit of sulfur dioxide in air is 0.003mg/m3. 1.2.3 Interference and elimination:
The main interferences are nitrogen oxides, ozone and some heavy metal elements. The sample can be left for a period of time to decompose the oxygen, adding sodium ammonium sulfonate solution can eliminate the interference of nitrogen oxides, and adding CDTA can eliminate or reduce the interference of some metal ions. When 50g of calcium, magnesium, iron, nickel, ammonium, copper ions and 5 divalent zirconium ions exist in 10mL of sample, there will be no interference in the determination. 2 Principle
Sulfur dioxide is absorbed by formaldehyde buffer solution to generate a stable hydroxymethylsulfonyl addition compound. Sodium hydroxide is added to the sample solution to decompose the addition compound, releasing sulfur dioxide to react with parabens and benzaldehyde to generate a purple-red compound, which is measured at 577nm with a spectrophotometer.
3 Reagents
Unless otherwise specified, analytical reagents and distilled water or water of equal purity that meet national standards are used in the analysis. 3.1 Sodium hydroxide solution, c(NaOH)-1.5mol/L. 3.2 Disodium cyclohexylaminetetraacetic acid solution, c(CDTA-2Va)=0.05mol/L. Weigh 11.82g trans-1,2-cyclohexylaminetetraacetic acid [(trans-1,2-cyclohcxylen cdinitrilw)tetraacetic acid, referred to as CITA]. Add 6.5mL of sodium hydroxide solution (3.4) and dilute with water to 1h mL. 3.3 Formaldehyde buffer solution storage solution,
Absorb 5.5ml of 36% formaldehyde solution. CDTA-2Ve solution (3.2) 20.n0mL, weigh 2.04K potassium hydrogen phthalate, dissolve in a little water: combine the solutions, dilute with water to 100ml, and store in a refrigerator for 1 year. 3.4 Formaldehyde buffer solution.
Dilute the formaldehyde buffer absorption solution stock solution (3.3) 100 times with water. Prepare it before use. 3.5 Sodium sulfamic acid solution, 0.6/100L.
Approved by the State Environmental Protection Agency on October 26, 1994, and implemented on June 1, 1995
GB/T 15262:-94bzxz.net
Weigh 1.60g of sulfamic acid (H2NS0,H) and place it in a 100rmL mother bottle, add 4.0mL of sodium oxychloride solution (3.1), dilute with water to the mark, and add a hook. This solution is sealed and can be used for 10 days. 3.6 Iodine stock solution + c = (1/2I2) = 0.1mol/1. Weigh 12.7 iodine (I.) into a beaker, add 40% potassium iodide and 25 mL water, stir until completely dissolved, dilute with water to 1 000 mL, store in a brown narrow-necked bottle, 3.7 iodine solution c (1/2I) 0.05 mal/L
Measure 250 mL of iodine solution (3.6), dilute with water to 500 mL, and place in a brown narrow-necked bottle. 3.8 Starch solution 0.5 g/100 ml.
Weigh 0.5 g of soluble starch, mix with a little water to make a paste, slowly pour into 100 mL of boiling water, continue to boil until the solution is clear, cool and store in a reagent bottle. Prepare before use.
3.9 Potassium iodate standard solution, c (1/6K103) = 0.1000 mol/L. Weigh 3.5667g potassium iodate (KIO: high-grade pure, dried at 110℃ for 2h) and dissolve it in water, transfer it into a 1000mL volumetric flask, dilute it to the chamber mark with water, and shake it well.
3.10 Acid solution (1+9)
3.11 Sodium thiosulfate stock solution, c(NaS0,): 0.10mol/L Weigh 25.0g sodium thiosulfate
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