There are several analytical methods for urea
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Dear sea friends, please talk about how many analysis methods there are for urea What are their respective features?
From Baidu: 1. Urea standard (GB-** Standard: GB 2440-2001) Standard category: GB-** Standard Number: GB 2440—2001 Standard name: Urea * ======================================================== 1. Scope This standard specifies the technical requirements, testing methods, inspection rules for urea, as well as its labeling, packaging, transportation, and storage. This standard applies to urea produced by the synthesis of ammonia and carbon dioxide, and is divided into two categories: industrial use and agricultural use. Its main use is as a fertilizer in agriculture, and as a raw material for industries such as plastics, resins, coatings, and pharmaceuticals in industry. Molecular formula: CO(NH2)2 Relative molecular mass: 60 055 (according to the 1997 International Table of Relative Atomic Masses) 2 References The provisions contained in the following standards become part of this standard by being referenced herein. At the time of publication of this standard, all versions shown are valid. All standards will be revised, and those using this standard should consider the possibility of using the latest versions of the following standards. GB/T 1250—1989 Methods for expressing and determining limit values GB/T 2441.1—2001 Method for determining urea – Determination of total nitrogen content GB/T 2441.2—2001 Method for determining urea – Determination of biuret content, spectrophotometric method (neqISO 2574:1973) GB/T 2441.3—2001 Method for determining urea – Determination of moisture content, Karl Fischer method (eqvISO 2573:1973) GB/T 2441.4—2001 Method for determining urea – Determination of iron content, o-phenanthroline spectrophotometric method (neq ISO 6685:1982) GB/T 2441.5—2001 Method for determining urea – Determination of alkalinity, volumetric method (neqISO 1593:1977) GB/T 2441.6—2001 Method for determining urea – Determination of water-insoluble matter content, gravimetric method GB/T 2441.7—2001 Method for determining urea – Determination of particle size, sieving method GB/T 2441.8—2001 Method for determining urea – Determination of sulfate content, visual turbidimetry method GB/T 2441.9—2001 Method for determining urea – Determination of methylenedihydrure content, spectrophotometric method GB/T 6679—1986 General rules for sampling solid chemical products GB 8569—1997 Packaging of solid chemical fertilizers GB 18382—2001 Labeling of fertilizers – Content and requirements (neqISO 7409:1984) 3 Requirements 3.1 Appearance: White or light-colored granules. 3 2 The requirements for urea shall comply with the provisions in Table 1. Table 1 Requirements for urea – Industrial use, Agricultural use
Grade: Top grade, First grade, Acceptable grade
Total nitrogen (N) (on a dry basis): # 46 5 46 3 46 3 46 4 46 2 46 0
Dicyandiamide: $ 0 5 0 9 1 0 0 9 1 0 1 5
Water (H2O) content: $ 0 3 0 5 0 7 0 4 0 5 1 0
Iron (as Fe): $ 0 0005 0 0005 0 0010
Alkalinity (as NH3): $ 0 01 0 02 0 03
Sulfates (as SO2-4): $ 0 005 0 010 0 020
Water-insoluble substances: $ 0 005 0 010 0 040
Methylenediamide (as HCHO): $ 0 6 0 6 0 6 d0 85mm! 2 80mm
# Note: 1 If formaldehyde is not used in the urea production process, it is not necessary to determine the methylenediamide content. For the 2 indicators, the granularity level only needs to meet any one of the four levels, and this should be indicated on the packaging label. 4 Test Methods 4.1 Determination of total nitrogen content: Conducted in accordance with the provisions of GB/T24411. 4.2 Determination of biuret content: Conducted in accordance with the provisions of GB/T24412. 4 3 Determination of moisture: Conducted in accordance with the provisions of GB/T2441 3. 4.4 Determination of iron content: Conducted in accordance with the provisions of GB/T2441.4. 4 5 Determination of alkalinity: Conduct in accordance with the provisions of GB/T2441 5. 4 6 Determination of water-insoluble matter: Conduct in accordance with the provisions of GB/T2441 6. 4 7 Determination of particle size is carried out in accordance with the provisions of GB/T2441 7. 4.8 Determination of sulfate content: Conduct in accordance with the provisions of GB/T2441.8. 4 9 Determination of methylenediurea content: Conduct in accordance with the provisions of GB/T2441 9. 5 Inspection Rules 5.1 For determining whether the indicators meet the requirements in this standard, the \"rounded value comparison method\" specified in GB/T1250—1989 is adopted. 5.2 The products shall be inspected by the quality control department of the manufacturing enterprise; the manufacturer must ensure that each batch of products released for sale meets the requirements of this standard, and each batch shall be accompanied by a quality certificate in a specified format. The certificate includes the following information: the name of the manufacturing enterprise, its address, the product name, trademark, product category, grade, particle size, batch number or production date, the net content of the product, and the standard number. 5.3 The user unit has the right to conduct quality inspections on the urea received in accordance with the provisions of this standard, to verify whether its parameters meet the requirements of this standard. 5 4 Products are inspected in batches, with the output of one shift or one day constituting one batch, and the maximum batch size not exceeding 1500t. The user treats the products accompanied by a quality certificate or those received as a batch. For products packaged in 5 or 5 bags, when the total number of packaging bags is less than 512, the number of samples to be taken is determined according to Table 2 ； When it is greater than 512, the number of sampling bags is determined based on the calculation using equation (1); if a decimal value results, it is rounded up to the nearest integer. Number of sampling bags = 3 × 3 × N …………………… Equation (1) Where: N———total number of bags per batch of products. Table 2 Determination of the number of sampling bags: Total number of bags, Minimum number of sampling bags. Based on the calculations in Table 2 or Equation (1), a random number of sampling bags is selected; using a sampler, samples of at least 100 g are collected from each bag by inserting the sampler along the longest diagonal up to three-quarters of the way into the bag. The total amount of sample collected per batch must be at least 2 kg. For bulk products, sampling shall be carried out in accordance with GB/T6679. 5, 6 The samples to be taken should be quickly reduced in size using a reducer or the quartering method; depending on the requirements for industrial and agricultural products, they should be reduced to sample weights of 600 g or 1200 g. These samples should then be placed in two clean, dry wide-mouth bottles or polyethylene containers with screw-on caps, sealed, and labeled with the name of the manufacturing company, product name, category, batch number, particle size range, date of sampling, and the name of the person who took the samples. One bottle is used for product quality analysis, and another bottle is kept for two months for reference. 5 7 If any one of the test results does not meet the requirements of this standard, samples should be taken again from twice as many bags for testing. Recheck the results; if even one parameter does not meet the requirements of these standards, the entire batch of products cannot be accepted. 5 8 When the supplier and the buyer have disputes regarding product quality, the relevant provisions of the \"Methods for Arbitration Inspection of Product Quality and Management of Product Quality Appraisal\" shall be followed. 6 Marking: The packaging bag shall indicate the particle size range; the category may not be indicated, and the remaining markings shall be in accordance with the provisions of GB18382. 7 Packaging, Transportation, and Storage 7.1 Urea is packaged in double-layer bags consisting of an outer plastic woven bag and an inner polyethylene film bag, or in composite plastic woven bags. The net content per bag is (25 0 25) kg, (40 0 4) kg, or (50 0 5) kg. The average net content per batch of product bags must not be less than 250 kg, 400 kg, or 50.0 kg. The quality of urea packaging shall comply with the relevant provisions of GB8569. 7 2 Urea can be transported by vehicles such as cars, trains, and ships. Transportation vehicles and handling equipment should be clean, smooth, and free of any protruding sharp objects to prevent puncturing or scratching of the packages. 7 3 Urea should be stored in a warehouse with a level floor, in a cool, well-ventilated, and dry environment. The packaging units should be stacked neatly, with the stacking height remaining below 7 meters. 7 4 During the transportation and storage of urea, it is necessary to take precautions against rain and sunlight. Appendix A (Suggested Appendix) Determination of ash in industrial urea – Gravimetric method A1 Scope This method specifies the gravimetric determination of the ash content in urea. This method is applicable to the determination of ash content in industrial urea produced by the synthesis of ammonia and carbon dioxide. A2 Method Summary: The sample is calcined at (800 25), and the residue is expressed as ash. A3 instruments: standard laboratory instruments and A3 1 platinum crucibles or quartz crucibles, with a flat bottom, diameter of 50mm and height of 25mm ； A3 2-chamber high-temperature furnace, capable of controlling (800 25). A4 Analysis steps: Weigh approximately 100 g of the sample, with an accuracy of 0.1 g, and place it in a clean container. Weigh a platinum or quartz dish that has been heated to constant weight at (800 25) and cooled in a desiccator (with precision to 0.001 g); place it over a low flame in a fume hood, add a small amount of the precisely weighed sample. Once it melts, add more of the remaining sample until all of it has been added and melted along with part of it having decomposed. Transfer the platinum or quartz vessel containing the melt to a high-temperature furnace at around 300 °C. To avoid spattering losses during heating, the temperature should be increased slowly to (800 ± 25) °C over a period of about 1 hour. Continue heating until the residue is completely burned off, which takes approximately 30 minutes. Once this is done, remove the platinum or quartz vessel and cool it in a desiccator to room temperature, then weigh it with an accuracy of 0.001 g. Repeat the process of heating, cooling, and weighing until the difference between two consecutive measurements is no more than 0.0005 g. Note: If the ash content is $0.001% or if iron content is to be determined using it, a platinum crucible should be used. Expression of A5 analysis results: The ash content (X) in the sample, expressed as a mass percentage (%), is calculated using equation (A1): mX = 2 – m1 / m × 100 ……………………(A1) Where: m1 —— the mass of the empty platinum or quartz crucible, in g ； m2———mass of the ash-containing platinum or quartz crucible, in g ； m———mass of the sample, g. The resulting value should be expressed to five decimal places. 2. Research on the high-performance liquid chromatography analysis method for urea: Link: http://www.cqvip.com/qk/92314X/200312/8728297.html. This post was last edited by lifanwang on 2009-2-15 08:40.]
Grade: Top grade, First grade, Acceptable grade
Total nitrogen (N) (on a dry basis): # 46 5 46 3 46 3 46 4 46 2 46 0
Dicyandiamide: $ 0 5 0 9 1 0 0 9 1 0 1 5
Water (H2O) content: $ 0 3 0 5 0 7 0 4 0 5 1 0
Iron (as Fe): $ 0 0005 0 0005 0 0010
Alkalinity (as NH3): $ 0 01 0 02 0 03
Sulfates (as SO2-4): $ 0 005 0 010 0 020
Water-insoluble substances: $ 0 005 0 010 0 040
Methylenediamide (as HCHO): $ 0 6 0 6 0 6 d0 85mm! 2 80mm
# Note: 1 If formaldehyde is not used in the urea production process, it is not necessary to determine the methylenediamide content. For the 2 indicators, the granularity level only needs to meet any one of the four levels, and this should be indicated on the packaging label. 4 Test Methods 4.1 Determination of total nitrogen content: Conducted in accordance with the provisions of GB/T24411. 4.2 Determination of biuret content: Conducted in accordance with the provisions of GB/T24412. 4 3 Determination of moisture: Conducted in accordance with the provisions of GB/T2441 3. 4.4 Determination of iron content: Conducted in accordance with the provisions of GB/T2441.4. 4 5 Determination of alkalinity: Conduct in accordance with the provisions of GB/T2441 5. 4 6 Determination of water-insoluble matter: Conduct in accordance with the provisions of GB/T2441 6. 4 7 Determination of particle size is carried out in accordance with the provisions of GB/T2441 7. 4.8 Determination of sulfate content: Conduct in accordance with the provisions of GB/T2441.8. 4 9 Determination of methylenediurea content: Conduct in accordance with the provisions of GB/T2441 9. 5 Inspection Rules 5.1 For determining whether the indicators meet the requirements in this standard, the \"rounded value comparison method\" specified in GB/T1250—1989 is adopted. 5.2 The products shall be inspected by the quality control department of the manufacturing enterprise; the manufacturer must ensure that each batch of products released for sale meets the requirements of this standard, and each batch shall be accompanied by a quality certificate in a specified format. The certificate includes the following information: the name of the manufacturing enterprise, its address, the product name, trademark, product category, grade, particle size, batch number or production date, the net content of the product, and the standard number. 5.3 The user unit has the right to conduct quality inspections on the urea received in accordance with the provisions of this standard, to verify whether its parameters meet the requirements of this standard. 5 4 Products are inspected in batches, with the output of one shift or one day constituting one batch, and the maximum batch size not exceeding 1500t. The user treats the products accompanied by a quality certificate or those received as a batch. For products packaged in 5 or 5 bags, when the total number of packaging bags is less than 512, the number of samples to be taken is determined according to Table 2 ； When it is greater than 512, the number of sampling bags is determined based on the calculation using equation (1); if a decimal value results, it is rounded up to the nearest integer. Number of sampling bags = 3 × 3 × N …………………… Equation (1) Where: N———total number of bags per batch of products. Table 2 Determination of the number of sampling bags: Total number of bags, Minimum number of sampling bags. Based on the calculations in Table 2 or Equation (1), a random number of sampling bags is selected; using a sampler, samples of at least 100 g are collected from each bag by inserting the sampler along the longest diagonal up to three-quarters of the way into the bag. The total amount of sample collected per batch must be at least 2 kg. For bulk products, sampling shall be carried out in accordance with GB/T6679. 5, 6 The samples to be taken should be quickly reduced in size using a reducer or the quartering method; depending on the requirements for industrial and agricultural products, they should be reduced to sample weights of 600 g or 1200 g. These samples should then be placed in two clean, dry wide-mouth bottles or polyethylene containers with screw-on caps, sealed, and labeled with the name of the manufacturing company, product name, category, batch number, particle size range, date of sampling, and the name of the person who took the samples. One bottle is used for product quality analysis, and another bottle is kept for two months for reference. 5 7 If any one of the test results does not meet the requirements of this standard, samples should be taken again from twice as many bags for testing. Recheck the results; if even one parameter does not meet the requirements of these standards, the entire batch of products cannot be accepted. 5 8 When the supplier and the buyer have disputes regarding product quality, the relevant provisions of the \"Methods for Arbitration Inspection of Product Quality and Management of Product Quality Appraisal\" shall be followed. 6 Marking: The packaging bag shall indicate the particle size range; the category may not be indicated, and the remaining markings shall be in accordance with the provisions of GB18382. 7 Packaging, Transportation, and Storage 7.1 Urea is packaged in double-layer bags consisting of an outer plastic woven bag and an inner polyethylene film bag, or in composite plastic woven bags. The net content per bag is (25 0 25) kg, (40 0 4) kg, or (50 0 5) kg. The average net content per batch of product bags must not be less than 250 kg, 400 kg, or 50.0 kg. The quality of urea packaging shall comply with the relevant provisions of GB8569. 7 2 Urea can be transported by vehicles such as cars, trains, and ships. Transportation vehicles and handling equipment should be clean, smooth, and free of any protruding sharp objects to prevent puncturing or scratching of the packages. 7 3 Urea should be stored in a warehouse with a level floor, in a cool, well-ventilated, and dry environment. The packaging units should be stacked neatly, with the stacking height remaining below 7 meters. 7 4 During the transportation and storage of urea, it is necessary to take precautions against rain and sunlight. Appendix A (Suggested Appendix) Determination of ash in industrial urea – Gravimetric method A1 Scope This method specifies the gravimetric determination of the ash content in urea. This method is applicable to the determination of ash content in industrial urea produced by the synthesis of ammonia and carbon dioxide. A2 Method Summary: The sample is calcined at (800 25), and the residue is expressed as ash. A3 instruments: standard laboratory instruments and A3 1 platinum crucibles or quartz crucibles, with a flat bottom, diameter of 50mm and height of 25mm ； A3 2-chamber high-temperature furnace, capable of controlling (800 25). A4 Analysis steps: Weigh approximately 100 g of the sample, with an accuracy of 0.1 g, and place it in a clean container. Weigh a platinum or quartz dish that has been heated to constant weight at (800 25) and cooled in a desiccator (with precision to 0.001 g); place it over a low flame in a fume hood, add a small amount of the precisely weighed sample. Once it melts, add more of the remaining sample until all of it has been added and melted along with part of it having decomposed. Transfer the platinum or quartz vessel containing the melt to a high-temperature furnace at around 300 °C. To avoid spattering losses during heating, the temperature should be increased slowly to (800 ± 25) °C over a period of about 1 hour. Continue heating until the residue is completely burned off, which takes approximately 30 minutes. Once this is done, remove the platinum or quartz vessel and cool it in a desiccator to room temperature, then weigh it with an accuracy of 0.001 g. Repeat the process of heating, cooling, and weighing until the difference between two consecutive measurements is no more than 0.0005 g. Note: If the ash content is $0.001% or if iron content is to be determined using it, a platinum crucible should be used. Expression of A5 analysis results: The ash content (X) in the sample, expressed as a mass percentage (%), is calculated using equation (A1): mX = 2 – m1 / m × 100 ……………………(A1) Where: m1 —— the mass of the empty platinum or quartz crucible, in g ； m2———mass of the ash-containing platinum or quartz crucible, in g ； m———mass of the sample, g. The resulting value should be expressed to five decimal places. 2. Research on the high-performance liquid chromatography analysis method for urea: Link: http://www.cqvip.com/qk/92314X/200312/8728297.html. This post was last edited by lifanwang on 2009-2-15 08:40.]