What are the test items of urea testing?

Urea testing items are:

Because of its nitrogen content of up to 46%, urea is often widely used as seed fertilizer, basal fertilizer, top dressing and foliar fertilizer in agricultural production. Of course, in addition to agricultural urea, there is also industrial urea. The urea testing indicators are nothing more than appearance, moisture, particle size, iron, alkalinity, total nitrogen (N) mass fraction, biuret mass fraction, methylene diurea mass fraction, sulfate, water insoluble matter and other items.

But what are the specific testing items for agricultural urea and industrial urea? And how does the state conduct random inspections of urea enterprises? You must still have questions about these questions, so let's explain them to you in detail.

The testing items of agricultural urea (fertilizer) mainly include total nitrogen, biuret, moisture, methylene diuret, particle size and other items, while the particle size of agricultural urea testing indicators needs to be marked on the outer packaging with the particle size range. The moisture index should be based on the data of the factory inspection. If formaldehyde is not added to urea during the production process.

Then the methylene diurea index does not need to be measured.

The testing items of industrial urea mainly include total nitrogen, biuret, moisture, iron, alkalinity, sulfate and water insoluble substances. It should be pointed out that industrial urea has no requirements for particle size, so there is no need to add formaldehyde to pursue urea granules to become larger and sustained, but if the production process requires addition, it must be indicated on the quality certificate that it contains formaldehyde.

There are 18 national standards for urea testing, including aldehydes, minerals, metals, refractive index, biuret, etc.!

1. Take some sample water from the swimming pool where the urea is tested (the best water intake depth is less than 20cm), and pour the water into the measuring cup to the marking line. Wash the measuring cup before using it and dry it with a clean cloth.

2. Take out a urease paper strip, put the end with the reagent into the sample water, stir it up and down by hand for 30s, take it out and throw it away.

3. The water sample returns to stand still for 2 minutes.

4. Then take a urea ammonia test strip (ammonia) and put the end with the yellow detection reagent into the sample water for about 5s

5. Take out the test strip, and put the test block facing up, do not shake off the excess water, and leave it for 90s.

6. Take out the test strip, keep the balance, and compare the color with the color card on the manual to get the result. To obtain accurate results, read the reaction under fluorescent or incandescent light.

After detecting urea in swimming pool water, you can use a special agent to remove urea in the water, among which Creed urea degrader is a water treatment agent specially used to solve the excessive urea in pool water, which can remove all urea in the water in 6 hours at the earliest, and there is no need to change the water.

In addition, we can use the method of supplementing new water to reduce the urea content in the water, which is slower and can be selected according to the user.

Methods for the determination of urea include chromatography, spectrophotometry, electrochemistry and instrumental analysis.

1. Chromatography: Chromatography is a common method for urea determination. NH3 released after the hydrolysis of urea is determined by a gas chromatograph after appropriate pretreatment.

2. Spectrophotometry: This method measures the content of urea by using the reaction of urea and bromic acid to obtain the absorption value of the reaction product.

3. Electrochemical method: the hydrolysis of urea can produce the properties of ammonia, the rock sample containing urea is heated and hydrolyzed, and the obtained NH3 is conducted to the electrode through the conductive battery, and the content of urea in the sample is calculated by using the measured current or potential.

4. Instrumental analysis: At present, there are some instruments, such as the automatic biochemical Sega wide instrument, which can catalyze the hydrolysis of urea by measuring lactate dehydrogenase (LDH), generate ammonia and calculate the content of urea.

Urea is an organic compound, a binary compound consisting of two amino groups with the molecular formula CO(NH2)2. Urea is a white crystalline brightening solid, which is easily dissolved in water and produces ammonia odor, which can be found in nature and can also be obtained by synthesis. Urea is converted from amino acids produced by protein breakdown in living organisms.

In plants, urea can also be produced through nitrogen fixation, which is synthesized and transported through the blood to the liver, and finally excreted by the kidneys.

Precautions for measuring urea

It should be noted that different determination methods have their own advantages and scope of application, and the appropriate determination method should be selected according to the specific situation. In addition, when performing urea measurement, it is necessary to pre-treat urine or blood samples to avoid the influence of interfering substances on the measurement results.

The common automotive urea testing authority has the following cavity structures:

1.U.S. Environmental Protection Agency (EPA);

2.European Union (EU);

3.International Organization for Standardization (ISO);

4.Japan National Institute of Quality Inspection and Technology (JIS);

5.National Institute of Quality and Technology (NIST);

6.National Institute of Quality Technology (NRC);

7.National Institute of Quality Technology (NRC);

8.Japan National Institute of Quality Inspection and Technology (JIS);

9.National Institute of Quality Technology (NRC);

10.National Institute of Quality and Technology (NIST);

11.National Institute of Quality Technology (NRC);

12.General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China (AQSIQ);

13.National Institute of Quality Technology (NRC);

14.General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China (AQSIQ);

15.Japan National Institute of Quality Inspection and Technology (JIS);

16.National Institute of Quality Technology (NRC);

17.National Institute of Quality and Technology (NIST);

18.General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China (AQSIQ);

19.National Institute of Quality Technology (NRC);

20.National Institute of Quality and Technology (NIST);

Automotive urea testing institution, Guoxian Zihonglian quality inspection, professional brother has CMA and CNAS qualifications of the third-party oil testing laboratory, has rich testing experience in automotive urea testing, can be based on the current national testing standards, local standards, etc., to control the quality of automotive urea, and issue test reports for national recognition.

The authoritative institutions commonly used in vehicle urea testing include Dongfeng Motor Company, South Korea Market Lianzhong Testing and Research Institute Duan Chong, and British An.

Full testing center, National Mechanical Engineering Testing Institute of the United States, etc. Grip and annihilation.

Determination of urea—neutralization titration method sock simple base.

Accurately weigh the test sample, put it in a Kjeldahl flask, add 25ml of water, 2ml of 3% copper sulfate solution and 8ml of sulfuric acid, slowly heat until the solution is clear green, continue to heat for 30 minutes, let it cool, add 100ml of water, shake well, slowly add 75ml of 20% sodium hydroxide solution along the wall of the bottle, form a liquid layer, add zinc granules, and connect the Kjeldahl flask with a condenser tube with a nitrogen balloon.

And the end of the condenser tube is stretched into the liquid surface of the 500ml Erlenmeyer flask containing 50ml of 4% boric acid solution, gently swing the Kjeldahl flask, mix the solution evenly, carefully heat the distillation, stop the distillation, and add a few drops of methyl red indicator solution to the distillate.

Titrate with hydrochloric acid solution (titration) and the results of the titration are corrected with a blank test. Per 1 ml of hydrochloric acid titration solution (equivalent to urea.

Determination of urea – neutralization titration.

Accurately weigh the test sample, put it in a Kjeldahl flask, add 25ml of water, 2ml of 3% copper sulfate solution and 8ml of sulfuric acid, slowly heat until the solution is clear green, continue to heat for 30 minutes, let it cool, add 100ml of water, shake well, slowly add 75ml of 20% sodium hydroxide solution along the wall of the bottle, form a liquid layer by itself, add zinc granules, and connect the Kjeldahl flask with the condenser tube with a nitrogen balloon.

And the end of the condenser tube is stretched into the liquid surface of the 500ml Erlenmeyer flask containing 50ml of 4% boric acid solution, gently swing the Kjeldahl flask, mix the solution evenly, heat and distill, until the ammonia is distilled, stop the distillation, and add a few drops of methyl red indicator solution to the distillate.

Titrate with hydrochloric acid solution (titration) and the results of the titration are corrected with a blank test. Per 1 ml of hydrochloric acid titration solution (equivalent to urea.

I finally found a method for the determination of urea, so complete.

Legal analysis: urea is easily soluble in water, 20 to 100 ml of water is soluble in 105 grams, and the aqueous solution is neutral. There are two types of urea products.

The crystal elements are white needle-like or prismatic crystal forms, with strong hygroscopicity, and form agglomerates after moisture absorption, and the hygroscopicity is 12 times faster than that of particles. Granular urea is a translucent particle with a particle size of 1 2 mm, which has a clean appearance and significantly improved hygroscopicity. At 20 o'clock, the critical moisture absorption point is 80% of the relative humidity, but at 30 o'clock, the critical moisture absorption point drops to, so it should be avoided in humid climates in the middle of summer.

The addition of hydrophobic substances such as paraffin wax to urea production results in a significant decrease in hygroscopicity.

1. Standard number: GB T

Standard name: sulfur-coated urea.

Standard Status: Active.

Standard type classification: > national standard GB

2. Standard number: HG

Standard name: urea for feed.

Standard type classification: > chemical standard HG

3. Standard number: HG T

Standard name: urea-ammonium nitrate solution.

Standard type classification: > chemical standards.

HGCICS classification: > fertilizers.

CCS classification: > fertilizers, pesticides.

Legal basis: Article 2 of the Standardization Law of the People's Republic of China The standards (including standard samples) mentioned in this law refer to the technical requirements that need to be unified in the fields of agriculture, industry, service industry and social undertakings.

Standards include national standards, industry standards, local standards, group standards, and enterprise standards. National standards are divided into mandatory standards and recommended standards, and industry standards and local standards are recommended standards.

Mandatory standards must be enforced. The State encourages the adoption of recommended standards.