Soil NPK sensor refers to the soil nitrogen, phosphorus and potassium sensor, also known as the soil nutrient speed tester, is suitable for detecting the content of nitrogen, phosphorus and potassium in the soil.
how the soil NPK sensor works ?
①: Combined assay
The existing combined determination methods can be divided into two categories, one is that two elements can be simultaneously determined in the prepared liquid to be tested, and the other is that three elements can be simultaneously determined. The methods for simultaneous determination of two elements in the liquid to be tested are divided into the combined determination method of phosphorus and potassium and the combined determination method of nitrogen and phosphorus. The combined determination methods of phosphorus and potassium mainly include the sodium carbonate melting method and the sodium hydroxide melting method, both of which belong to the alkali melting method. , dissolved in dilute acid to make the solution to be tested. The application of alkali fusion method can fully decompose the soil, especially the sodium carbonate fusion method, the decomposition is complete and the accuracy is very high. However, due to the need for expensive platinum crucibles, it is difficult for ordinary laboratories to do it.
The sodium hydroxide melting method is slightly inferior to the sodium carbonate melting method in terms of soil decomposition, but its accuracy is still good, and a silver crucible or a nickel heap can be used instead of a platinum crucible. Therefore, these two methods are widely used.
②: Atomic absorption spectrometry
Atomic absorption spectrometry is mostly determined by diluting and adding absolute salt as an ionization inhibitor. In this way, analysis procedures and reagent consumption can be increased. At the same time, a large amount of dilution can also introduce analysis errors. Atomic absorption spectrometry is used under the sub-sensitive line. There are not many reports on the direct determination of high content of potassium. In this method, the conditions for the determination of high-content potassium by sub-sensitive line atomic absorption spectrometry were tested in detail, and the appropriate method was determined. The results are consistent with the standard value and the gravimetric method.
③ : Spectrophotometry
Digest by sodium hydroxide melting method, adjust the pH value, add ascorbic acid solution and ammonium molybdate salt solution for color development for 15min, use a 30mm cuvette with water as a reference. Measure the absorbance at a wavelength of 700nm, and find out the total phosphorus in the soil . The method is simple and reliable, and can meet the needs of environmental monitoring for the analysis of total phosphorus in soil.
④: Perchloric acid-sulfuric acid rapid digestion, diffusion nitrogen determination method
Method principle: Soil samples were digested with sulfuric acid. With the participation of strong oxidant perchloric acid, organic nitrogen was decomposed and converted into ammonia, and combined with sulfuric acid to form ammonium sulfate. Then remove a part of the digestion solution, move it to a comfort dish, add alkali to diffuse ammonia, absorb it with boric acid, and titrate with standard alkali.
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