Method for measuring kalium in soil by tetraphenylboron sodium nephelometery and its screening agent

Abstract

The invention discloses a method for measuring potassium by the sodium tetraphenylborate turbidimetry and a masking agent which is used by the method. The masking agent is a water solution containing 0.01 to 0.04mol / l of Cu<2+>, 0.04 to 0.10mol / l of tartaric acid and 5 to 10mol / l of H<+>; the method for measuring the potassium by the sodium tetraphenylborate turbidimetry is that: the masking agent is used for masking ammonium ion and other interfering ions in liquid under test, basic EDTA disodium salt solution is further added to carry out the auxiliary masking, basic sodium tetraphenylborate water solution is finally added, and the turbidity measurement is immediately carried out after shaking the reaction solution well. The measurement method has the advantages of simple operation, rapid and accurate measurement and low cost; the linear range thereof meets the requirements of the rapid measurement, which is suitable for the application of grass roots and agriculture popularization departments; and the masking agent used does extremely small harm to the human body and the environment.

Description

technical field [0001] The invention relates to the field of laboratory analysis, in particular to a method for measuring potassium in soil by sodium tetraphenylborate turbidimetry and a low-toxic environment-friendly masking agent. Background technique [0002] The nutrient level of soil potassium mainly depends on the content of available potassium in the soil. The content of available potassium in the soil is an effective indicator for evaluating the level of soil potassium and predicting the response of plants to potassium application. Timely measurement of the content of available potassium in the soil can help to understand its changing trend. It is very necessary to guide the rational application of potassium fertilizer. [0003] At present, the methods for the determination of available potassium in soil mainly include gravimetric method, volumetric method, colorimetric method, turbidimetric method, flame photometer method, atomic absorption method, electrode method ...

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Problems solved by technology

Colorimetric method mainly refers to crown ether DPDB-18-C-6 and bromothymol blue ion-pair extraction photometric colorimetric method, which is rarely used due to the complicated extraction steps in this method; turbidimetric method mainly includes tetraphenylboron Sodium method and sodium cobalt nitrite method, because the sodium cobalt nitrite reagent is highly toxic and expensive, so the sodium cobalt nitrite method is rarely used. The sodium tetraphenylborate turbidimetric method has been the most commonly used method for many years. It is relatively simple to operate, has a certain simplicity and reliability, meets the requirements of rapid measurement, and is widely used. However, in the determination of potassium by sodium tetraphenylborate method, the NH in the sample 4 + It also reacts with sodium tetraphenylborate to generate a white precipitate {K + +Na〔B(C 6 h 5 )X]=K[B(C 6 h 5 ) 4 〕↓+Na + }, thereby interfering with the determination of potassium

Formaldehyde-EDTA joint masking of NH by traditional sodium tetraphenylborate method 4 + and other metal ions [4NH 4 + +6HCHO=(CH 2 ) 6 N 4 +6H 2 O+4H + ], its masking effect is acceptable (up to 100mg / kg), but there are also the following problems that cannot be ignored: ①The formaldehyde used is poisonous and volatile, and the volatilized formaldehyde is a colorless harmful gas with an obvious pungent smell. Contact may cause nasal cavity, oral cavity, throat, skin and digestive tract cancer, which not only pollutes the environment, but also endangers the health of laboratory personnel; ②Formaldehyde is not easy to store for a long time, and it is easy to form polymers and become invalid; ③Waste liquid is difficult to handle

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