This standard is part 9 of GB/T 2441 "Determination of urea". This standard specifies the determination of methylene diurea content in urea by chromotropic acid spectrophotometry with disodium naphthalene disulfonic acid. This standard is only applicable to the determination of methylene diurea content in urea containing a small amount of methylene diurea. GB/T 2441.9-2001 Determination of urea Determination of methylene diurea content Spectrophotometric method GB/T2441.9-2001 Standard download decompression password: www.bzxz.net

GB/T 2441.9-~-2001
This standard is Part 9 of GB/T2441 “Determination method of urea”. GB/T2441 also includes the following parts:
Part 1 GB/T2441.1--2001
Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
GB/T 2441.2—2001
GB/T 2441.3—2001
GB/T 2441. 4--2001
GB/T 2441. 5--2001
GB/T 2441.6—2001
GB/T 2441. 7--2001
GB/T 2441.8--2001
Urea determination method
Determination of total nitrogen content
Urea determination method
Urea determination method
Urea determination method
Determination of dihydrogen phosphate content Spectrophotometric method
Determination of water content, Karl Fischer method
Determination of iron content O-phenanthroline spectrophotometric method Determination of alkalinity Volumetric method
Urea determination method
Gravimetric method
Urea determination method Determination of water-insoluble matter content Urea determination method Determination of particle size Sieving method Urea determination method Determination of sulfate content Visual turbidimetric method This standard is proposed by the State Bureau of Petroleum and Chemical Industry. This standard is under the jurisdiction and interpretation of the National Technical Committee for Standardization of Fertilizers and Soil Conditioners. This standard was drafted by: National Fertilizer Quality Supervision and Inspection Center (Shanghai), PetroChina Urumqi Petrochemical Company Fertilizer Plant, Sinopec Jiujiang Branch, Hainan Fudao Chemical Co., Ltd. The main drafters of this standard are: Zhang Qiuzhen, Li Zifen, Sha Yanping, Jiang Jianxin, Guo Zu, Yang Jiqun. 98
1 Scope
National Standard of the People's Republic of China
Determination of urea
Determination of methylenediurea contentSpectrophotometric methodwwW.bzxz.Net
GB/T 2441.9—2001
This standard specifies the determination of methylenediurea content in urea by spectrophotometric method using disodium naphthalene disulfonic acid (chromotropic acid). This standard is only applicable to the determination of methylenediurea content in urea containing a small amount of methylenediurea. 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard by being cited in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. HG/T2843-1997 Commonly used standard titration solutions, standard solutions, reagent solutions and indicator solutions for chemical analysis of fertilizer products 3 Principle
Under the action of concentrated sulfuric acid, methylene diurea in urea decomposes to form formaldehyde and urea. Formaldehyde reacts with disodium naphthalene disulfonic acid (chromotropic acid) to form a purple-red complex, and its absorbance is measured by a spectrophotometer at a wavelength of 570nm. 4 Reagents and solutions
4.1 Sulfuric acid;
4.2 Disodium naphthalene disulfonate (chromotropic acid) solution, 10 g/L; 4.3 Formaldehyde standard solution
4.3.1 Sodium sulfite solution (126 g/L): Weigh 126 g of sodium sulfite, dissolve in water, dilute to 1000 mL, add (10 drops) thymol acid indicator solution (1 g/L), and neutralize with sulfuric acid solution (1+19) until colorless. 4.3.2 Determination of formaldehyde content: Measure 3 mL of formaldehyde solution and weigh (accurate to 0.0002 g), place in a conical flask containing 50 mL of sodium sulfite solution, and titrate with sulfuric acid standard titration solution c(1/2H,SO,)-1 mol/L until the solution changes from blue to colorless. The formaldehyde content (X) is expressed as the mass percentage (%) of formaldehyde (HCHO) and is calculated according to the formula (1): X = V × 0.030 03 × 100
wherein c is the concentration of the standard sulfuric acid titration solution, mol/L; V is the volume of the standard sulfuric acid titration solution consumed, mL; - the mass of the formaldehyde solution, g;
·(1)
0.03003 - the mass of formaldehyde in grams equivalent to 1.00ml of the standard sulfuric acid titration solution [c (1/2H2SO.) = 1.000mol/L].
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on July 26, 2001, implemented on January 1, 2002
GB/T 2441.9—2001
4.3.3 Preparation of 1 mg/mL formaldehyde standard solution: Calculate according to formula (2), weigh the formaldehyde solution (4.3.2), place it in a 1000 mL volumetric flask, add water to dilute to the scale, and shake well.
Calculation of the mass (m) of formaldehyde solution:
Where: m is the mass of formaldehyde solution·g;
Formaldehyde content.%;
1.000).Concentration of formaldehyde standard solution.mg/mL. (2)
4.3.4 Preparation of formaldehyde standard solution (0.02 mg/ml): Pipette 10.0 mL of formaldehyde standard solution (4.3.3) into a 500 mL volumetric flask, dilute to the mark with water, and shake well (this solution is prepared before use). 5 Instruments
General laboratory glassware and
5.1 Spectrophotometer with 1 cm absorption cell. 6 Analysis steps
6.1 Plotting of standard curve
6.1.1 Preparation of standard colorimetric solution:
According to Table 1, add formaldehyde standard solution (4.3.4) into 6 100 mL volumetric flasks respectively. Table 1 [
Amount of formaldehyde standard solution added
Volume of formaldehyde standard solution ml.
Corresponding formaldehyde content, mg
Each volumetric flask is treated at the same time according to the following regulations: Add 1ml of disodium naphthalene disulfonic acid salt (chromotropic acid) solution, slowly add 10mL of sulfuric acid against the wall, shake well, and let it stand for 15min. Carefully add water to dilute to about 80ml. Shake well. After cooling again, dilute with water to the scale and shake well. 6.1.2 Absorbance determination
Use the solution with zero formaldehyde content as the reference solution, and use a spectrophotometer to determine the absorbance of each standard colorimetric solution (6.1.1) at a wavelength of 570nm.
6.1.3 Drawing of standard curve
Use the formaldehyde content (mg) in 100mL of standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis to draw a graph, or find the linear regression equation.
6.2 Determination
6.2.1 Preparation of test solution
Weigh the sample according to Table 2 (accurate to 0.002g), place it in a 100mL beaker, add a small amount of water to dissolve the sample, transfer it quantitatively to a 500mL volumetric flask, add water to dilute to the scale, shake well and transfer 5.0mL to a 100mL volumetric flask. The following operations are carried out according to the steps in 6.1.1 for color reaction.
Table 2 Weighing amount of laboratory samples
Formaldehyde (X).%
Test material mass g
0.10
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