SU1539615A1 - Method of chemiluminiscent determination of nitrogen in soil and vegetation samples - Google Patents

Abstract

The invention relates to analytics and allows the determination of nitrogen content in soil and plant samples. The aim of the invention is to increase the reliability of the chemiluminescent determination of the nitrogen content in soil and plant samples by providing the same degree of conversion of nitrogen-containing compounds of different structure to nitric oxide. The goal is achieved in that the products of destruction of the sample after the secondary heating zone are additionally passed through the catalytic oxidation-reduction zone with a temperature of 750-850 ° C, and this zone is located immediately after the combustion furnace and the secondary heater. 1 dw., 2 tab.

Description

The invention relates to agriculture and forestry and can be used in the analysis of soil and plants for nitrogen content.

The aim of the invention is to increase the reliability of the chemiluminescent result of nitrogen determination by providing the same degree of conversion of nitrogen-containing compounds of different structure to nitrogen oxide.

The drawing shows a diagram of a device explaining the proposed method of chemiluminescent determination of nitrogen content.

The device includes a sample introduction system 1, a temperature-controlled combustion chamber 2, a secondary heater 3, a catalytic oxidation zone 4 which is connected to a chemiluminescent detector 5. The combustion chamber is part of a quartz or ceramic tube with an electric heater, the secondary heater is also a quartz or a ceramic tube, which may be an extension of the burning chamber and the dimensions of which provide a contact time of at least 0.5 s. The catalytic oxidation zone is a quartz, ceramic, or metal reactor containing an oxidation catalyst, such as copper oxide.

The temperature of the combustion chamber is set from 500 to 900 ° C (depending on the type of material being analyzed) or a programmed temperature increase is carried out from 25 to 900 ° C. Optimal temperature

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the burning or the type of temperature program (the highest temperature and the rate of temperature increase) are selected based on the type of material being analyzed so as to ensure the best reproducibility and accuracy of the results. The temperature of the secondary heater is from 1000 to 1100 C. The temperature of the catalytic oxidation zone is chosen depending on the type of catalyst, for example, for copper oxide, the optimum temperature is 750-850 ° C.

A sample of 1–10 mg sample in a quartz boat is placed in a burning chamber and heated at 500–900 ° C or with a programmed temperature increase in a stream of oxygen-containing gas.

The products of combustion and destruction go to the secondary heater and then to the catalytic oxidation zone and to the chemiluminescent detector. The detector includes an ozone generator, a reaction chamber in which ozone and N0 react, and a photomultiplier that detects chemiluminescent radiation

Pure oxygen, a mixture of oxygen with an inert gas or air can be used as the oxygen-containing gas. Gas consumption 0.5 - 1.5 l / min. The duration of burning is determined by the duration of chemiluminescent radiation and is usually 1-4 minutes.

The method is illustrated by the following examples.

Example 1. A device was used, which included a probe-in system, on which the holder of a boat with a sample was attached, and a sealable shutter, a burning chamber (a part of a quartz tube 0.5 cm in diameter and 8 cm long with an electric heater, temperature controller and programmer) secondary heater (continuation of the same quartz tube with a diameter of 0.5 cm and a length of 25 cm) and a catalytic oxidation zone (a quartz tube with a length of 20 cm and an internal diameter of 1 cm, filled with copper oxide). The catalytic oxidation zone was connected to a chemiluminescent GHL-1 detector with a glass tube 40 cm long and 0.4 cm in diameter. A sample was placed in the burning chamber.

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5–10 mg in a quartz boat and heated the chamber to 700 ° C, blowing it with an air flow of 1.5 l / min. Gases burned and the oxidation products that did not have time to oxidize entered the secondary heater with a temperature of 1050 ° C, then into the catalytic oxidation zone with a temperature of 800 ° C and a chemiluminescent detector.

Pure chemical compounds containing various forms of nitrogen were analyzed: ammonium salts, nitrates, amino acids, aromatic heterocyclic compounds, soil standard samples, and also a soil sample subjected to hydropyrolysis, as a result of which only polycyclic aromatic hydrocarbons and heteroatomic compounds remain in the sample.

The results of determining the nitrogen content in these samples are given in Table. 1. For comparison, the results obtained on the same system without a catalytic oxidation zone are given. The standard deviation of the results of five parallel measurements is 0.01%.

The results in the table show that the measured contents of total nitrogen are in good agreement with the true values calculated by empirical formulas for pure compounds or measured by independent methods for other samples. In the absence of a catalytic oxidation zone, lower results are obtained, which indicates a less complete transition of nitrogen contained in the analyzed samples to nitrogen oxide, and the degree of this transition is different for different substances (from 0.76 to 0.93).

Example 2. Using the device described in Example 1, a standard SP-1 soil sample was analyzed under various experimental conditions.

The measurement results are shown in Table. 2 show that changing the parameters within the specified limits does not affect the measurement results.

Thus, the proposed technical solution provides an increase in the reliability of the results of determining the nitrogen content in soil and plant samples in comparison with the prototype by eliminating the dependence of the degree of conversion of nitrogen-containing compounds of the material under analysis into nitric oxide.

Claims (1)

Invention Formula The method of chemiluminescent determination of nitrogen content in soil and plant samples, including the burning of the sample at 700-900 ° C and passing the products of burning through the secondary heating zone at 1000 - 1100 ° C, leading to the destruction of the past radiation during the reaction of nitric oxide with ozone, according to which The amount of nitrogen-containing compounds in the sample, characterized in that, in order to increase the reliability of the determination results by providing the same degree of conversion of nitrogen-containing compounds of different structures to nitric oxide , Degradation products of the sample after the second heating zone is further passed through the catalytic zone with an oxidation-reduction oxide the registration of chemiluminescent is 15 MEDI AT 750 - 850 C. Results of determination of nitrogen content in soil and plant samples (May.%) table 2 The results of determining the nitrogen content in the standard soil sample SP-1 under different conditions (May.%) 1050 1050 1050 Table 1 0.28 0.29 0.29 Compiled by B.Shirokov Editor A.Makovska Tehred M.Hodanich Proofreader N.Korol Order 212 Circulation 503 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101 Subscription