The nitrogen meter still is designed according to the Kjeldahl method, which is mainly used to detect the content of ammonia nitrogen, protein nitrogen and other contents in grains, food, dairy products, beverages, feed, soil, water, drugs, sediments and chemicals. QYKDN series nitrogen determination meter still has beautiful appearance, easy to operate, adopts microcomputer for process control, and has the functions of automatic distillation control, automatic water addition, automatic water level control, automatic water stop and so on. Its function is that tap water (purified water) enters the steam generator after passing through the condenser and voltage regulator to produce continuous and stable vapor, distilling the digested sample, and calculating the protein content of the sample by titration.
Kjeldahl nitrogen analyzer is also known as nitrogen analyzer and protein analyzer. It works by coheating organic compounds with sulfuric acid so that the nitrogen in them is converted into ammonium sulfate. In this step, potassium sulfate is often added to the mixture to raise the boiling point of the intermediate. The end point of the analysis process of the sample is easy to judge, as the mixture changes from a dark color to a colorless and transparent color. A small amount of sodium oxide is added to the resulting solution and a distillation step is carried out, which converts the ammonium salt into ammonia. The total ammonia amount, which is directly determined by the nitrogen content of the sample, is determined by back-titration, and the end of the condenser tube is immersed in a boric acid solution. At this time, the ammonia reacts with the acid. Excess acids are titrated with sodium carbonate under the instructions of methyl oranges. The result can be obtained by multiplying the titrated junction by a specific conversion factor. Then the general applicability of the current Kjeldahl method. Accuracy and repeatability have been widely used and recognized internationally. It has been identified as a standard method for detecting protein content in foods.
A Kjeldahl nitrogen meter is an instrument used to measure the nitrogen content of a substance. It is widely used in agriculture, environment, chemistry, biology and other fields, because nitrogen is a very important element in living organisms, which can affect the growth and development of organisms and nutrient absorption.
1. Preparations.
Before using a Kjeldahl nitrogen analyzer, you first need to understand the structure and function of the instrument, which consists of two main parts - the digestion part and the measurement part. The digestion part is used to convert samples such as plants, soil, wastewater, etc., into ammonia, while the measurement part is used to measure the ammonia content. Therefore, the following work needs to be paid attention to in the digestion and measurement process of the sample.
1.Sample preparation: The first step is to select a well-representative sample and make it into a homogeneous powder or granule. Soil samples should be screened, plant samples should be removed from impurities and foreign matter, and wastewater samples should be precipitated and filtered first. The sample weight is generally 0Between 1g and 2g, the specific amount should be determined according to different samples.
2.Reagent preparation: Kjeldahl nitrogen analyzers require a variety of reagents. For example, sodium hydroxide, basic mercuric chloride, sulfuric acid, etc. These reagents need to be mixed in certain proportions and need to be prepared with care for safety.
3.Instrument preparation: Before using a Kjeldahl nitrogen determination instrument, it needs to be checked and adjusted to ensure the proper operation of individual components. This includes, but is not limited to, agitators, solenoid valves, samplers, thermometers, pressure gauges, etc.
2. Steps.
1.Digestion process: weigh the sample into the digestion tube, add an appropriate amount of reagent, and seal, the digestion tube is placed in a thermostat, and the digestion process is carried out in an acidic environment, the digestion process generally lasts 1-3 hours, the specific time is determined according to the sample type and content, after digestion, the sample is cooled and filtered.
2.Measurement process: Put the filtered sample solution into the measuring device, add the indicator and heat it in a hot water bath, the ammonia in the sample reacts to form ammonia salt, and the color of the solution will also change. Based on the degree of discoloration and the standard curve, the ammonia content is measured. It should be noted that the measurement temperature needs to be controlled and the gas flow in the equipment needs to be maintained during the measurement process to ensure the accuracy of the measurement results.
3. Precautions.
1.Safe operation: The process of digestion of reagents and samples will produce toxic gases, so it is necessary to wear appropriate safety protection equipment, avoid direct contact with reagents, and try not to press the window or vent.
2.Correct calibration: Calibration is the key to ensure the accuracy of measurement results, which requires calibration of instruments and reagents, and the development of corresponding measurement standard curves and correction factors.
3.Good experimental environment: It should be operated in a clean, well-ventilated laboratory and avoid dust. Odor and other interference tests.
4.Pay attention to sensitivity: Kjeldahl nitrogen determination instrument has a certain sensitivity, too high or too low sample content may affect the test results, so it is necessary to select the appropriate sample volume and measurement range.
Precautions and maintenance of the instrument.
1. When using the digester, the exhaust gas device should be covered, and the water in the pipe should be poured out in time when the sound of water is heard.
2. Do not set the temperature and time of the digester frequently, so as not to break some keys.
3. When the digester is working, the condensate and power switch at the exhaust gas should be turned on in time, and the number of improvements should be adjusted.
4. When the digester cannot work normally due to high temperature, press a small button at the back.
5. After each use of the digester, wipe it with a rag to avoid rust.
6.The distiller must be checked to see if the condensate is open when in use, and the digestion tube should be pressed tightly when distilling to avoid leakage.
7. When the indicator light marked with water, boric acid, and sodium oxide is on, check whether the sample solution is missing, and make up for it in time.
8. After each use of the still, distilled water should be air-steamed once to achieve the purpose of cleaning the inside, and the empty bottle and distilled water should be air-steamed once before use.
9. After the distiller is used up, the parts that are easy to get dirty should be carefully wiped to avoid corrosion by sodium oxide.
10. After the automatic titrator is used up, rinse the electrode with distilled water, and cover the electrode cap in time. Check whether the electrode protection solution in the cap is missing every time you cover the electrode cap and fill it up in time.
11. When there is a deviation in the reading of the automatic titrator, a special electrode correction solution should be used for correction.
12. The distilled water in the receiver should be replaced every three experiments, and the discoloration of the sodium oxide indicator must be replaced.
13. After each experiment, clean all dirty parts and pour out the waste liquid. Wipe all instruments clean.