RU2578955C1 - Method for automated direct determination of phosphorus available for plants in carbon-ammonium soil extract, coloured with humic compounds, and devices therefor - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: group of inventions relates to analysis of soils and can be used for estimation of agricultural land fertility. Method for automated direct determination of available to plants phosphorus in carbon-ammonium soil extract, coloured by humic compounds, consists in the fact that there is performed simultaneous two-channel spectrophotometry and measurement of optical density of hydraulic flows in the spectral range of 898-900 nm of one specimen of obtained extract sample at a flow-type auto-analyser: in one channel - by addition of reagents for colouring of phosphorus, and in the other channel - by addition of reactants without colouration of phosphorus. Difference in measurements of optical density of the same specimen in two channels characterises the content of phosphorus, available for plants, without taking into account the phosphorus making part of an organic component of the extract and not available for plants. Group of inventions also refers to an autoanalyzer for direct determination of available to plants phosphorus in soil extract and to a bubble separator for removal of air bubbles from the flow in front of the cuvette of the colorimeter of the said device.

EFFECT: higher efficiency and accuracy of analysis.

3 cl, 2 dwg

Description

Purpose and scope.

The scope of the invention relates to chemical methods of soil analysis using flow analyzers, for example, in assessing the fertility of agricultural land.

The invention, for example, can be effectively used in analytical laboratories when measuring the concentration of mobile mineral forms of phosphorus in soil samples with its extraction with a carbon ammonium extractant.

There is a method of determining mobile phosphorus in a carbon ammonium extract from soils (GOST 26205-91. Determination of mobile forms of phosphorus and potassium according to the Machigin method in the modification of TsINAO).

The soil extract obtained in this way is very often colored with organic (humic) compounds in brown. To prepare for colorimetric measurements in the spectral range 600–750 nm, this extract is clarified by oxidizing organic compounds with a mixture of sulfuric acid and potassium permanganate in conical flasks or test tubes made of heat-resistant glass. After that, a reagent for staining phosphorus is added to the hood and colorimetric is performed.

The organic component of the extract contains organically bound phosphorus, which is not directly accessible to the plant. During the oxidation of the extract by the above-mentioned method, organically bound phosphorus passes into the mineral fraction and, thereby, increases the content of mobile forms of phosphorus, distorting information about the supply of plants with this element. This is discussed in detail in the book “Automation of analytical work and instrumentation for monitoring soil fertility and crop production quality”. Authors Yu.M. Loginov, A.N. Sagittarius, pp. 96-108. Moscow. Agribusiness Center. 2010.

There is a method of direct measurement of the concentration of mobile mineral forms of phosphorus in soil samples when it is extracted with a carbon ammonium extractant and a device for its implementation (Patent for invention No. 2474809 RU).

In this method, there is no complex chemical preparation of the hood for colorimetry. The resulting soil extract is immediately mixed with a coloring reagent. The carbon dioxide released in this case is removed from the solution by vacuum, and the soil extract thus prepared is colorimetric in the spectral range 898–900 nm. In this measurement range, colored organic compounds practically do not interfere with the determination of phosphorus. The effect of organic compounds on the correct determination of available phosphorus can be observed only in those cases when the samples contain a very large amount of humus (more than 6-7%) and the optical density of extracts from these samples is more than 0.10 E at λ = 710 in plane-parallel a cuvette with a base of 10 mm.

The removal of carbon dioxide is necessary so that the bubbles of the indicated gas do not overlap the light flux in the measuring cell of the colorimeter and make it possible to work using a flow cell, which simplifies and speeds up the colorimetry.

The specified method simplifies the sample preparation of samples for analysis, increases the productivity and quality of analytical work when measuring the concentration of mobile mineral forms of phosphorus in soil samples after extraction with carbon ammonium extractant.

However, when obtaining a soil extract, which is very strongly colored with humic compounds, it is necessary to measure the phosphorus concentration twice: first, the solution is photographed with a staining phosphorus reagent, then the same extract is photographed without a staining phosphorus component.

The difference between the measurements obtained in the first and second cases will determine the content of mobile mineral phosphorus in the initial soil extract.

In addition, all technological and chemical operations in the analysis of soil extracts in this way must be carried out manually.

As a prototype of the invention, it seems to us possible to use the known method of direct measurement of the concentration of mobile mineral forms of phosphorus in soil samples when it is extracted with a carbon ammonium extract (OST 10 256-2000. Soils. Methods for measuring concentrations of mobile mineral forms of phosphorus and potassium according to the TsINAO technology in a carbon ammonium extract from soils according to Machigin).

When measuring the concentration of mobile mineral forms of phosphorus in soil samples in this way (an automated version of the determination), it is necessary to measure twice the same extract or use two separate samples of the same extract. This reduces productivity and increases the volume of sample used for analysis.

In the non-automated version of the analysis in this way, there is no operation to remove the carbon dioxide released from the solution by mixing the soil extract with a reagent staining the mineral forms of phosphorus. This leads to a deterioration in the quality and accuracy of the determination of phosphorus and does not make it possible to use a flow cell for colorimetrication of colored solutions, which dramatically reduces the productivity of analytical work.

The proposed method for automated direct determination of phosphorus available to plants in a carbon ammonium soil extract stained with humic compounds, and devices for implementing the method allow to fully automate the process of determining this indicator in the obtained extract, taking into account the influence of the organic component on the measurement results in all measured samples. In this case, the obtained extract sample is analyzed on a flow-type autoanalyzer with spectrophotometric termination in the spectral range 898-900 nm, two-channel spectrophotometry of one sample is carried out simultaneously: in one channel with the addition of reagents for staining phosphorus, and in the other channel with the addition of reagents without staining of phosphorus, automated the calculation of the difference in the results of the two channels determines the content of phosphorus available to plants, excluding the phosphorus in the organic ponent drawing and are not available to plants.

The hydraulic circuit of the autoanalyzer with explanations is shown in FIG. 1. The amount of carbon dioxide released, which must be reliably removed from the hydraulic system, is ensured by the design of the bubble separator (Fig. 2) and the normalization of the released volume of carbon dioxide. This volume is determined by the volume of the separation chamber of the bubble separator and is ensured by the ratio of the capacities of the hydraulic channel of the selected soil extract sample and the hydraulic feed channel of the coloring reagent. In addition, the removal of bubbles before the flow enters the colorimeter cuvette is forcibly provided by a separate channel, the productivity of which is higher than the productivity of the channel taking a sample in the colorimeter cuvette. The remaining carbon dioxide that has not been removed is redissolved in the liquid as a result of its cooling and does not interfere with the measurement of the optical density of the solution.

Analytical training and analysis technology is carried out according to OST 10 256-2000. The proposed method doubles the productivity of the analysis and increases the accuracy of the measurement of phosphorus available to plants.

The hydraulic circuit of the device is shown in FIG. 1. Signatures and explanations in the drawing.

Thus, we declare the following.

1. A method for automated direct determination of phosphorus available to plants in a carbon ammonium soil extract stained with humic compounds, namely, that the obtained extract sample is analyzed on a flow-type autoanalyzer with spectrophotometric termination and measurement of the optical density of hydraulic flows in the spectral range of 898-900 nm, characterized in that simultaneous two-channel spectrophotometry of one sample is performed: in one channel with the addition of reagents for staining I have phosphorus, and in another channel with the addition of reagents without staining phosphorus, the automated calculation of the difference in the results of the two channels determines the content of phosphorus available to plants, excluding phosphorus, which is part of the organic component of the extract and not available to plants; the normalized amount of released carbon dioxide when mixing soil extracts with reagents when heated is guaranteed to be removed from the hydraulic stream, and the remaining carbon dioxide is dissolved in the liquid as a result of its cooling and does not interfere with the measurement of the optical density of the solution. This doubles the productivity of the analysis and increases the accuracy of the measurement of phosphorus available to plants.

2. An autoanalyzer for the direct determination of phosphorus available to plants in a soil extract stained with humic compounds, consisting of a sample feeder 8, a container with distilled water 9, a sample separator 7 into two channels, a multi-channel peristaltic pump 2, a hydraulic system with mixers 3, 11, thermostats 4, 12, cooling devices 5, 13, spectrophotometers 6, 14, a collector 15, and a computer system (not shown in FIG. 1), characterized in that the hydraulic system [FIG. 1] includes two spectrophotometers 6, 14, which simultaneously receive the measured sample of the hood and which determine the optical density of the sample through one channel with the addition of reagents for staining phosphorus 1, and in the other channel with the addition of reagents without staining phosphorus 10, the difference in optical measurements the density of the same sample in two channels characterizes the content of phosphorus available to plants, excluding phosphorus, which is part of the organic component of the extract and not accessible to plants. The proposed design of the autoanalyzer simplifies the analysis and increases the productivity of analytical work.

3. The bubble separator [Fig. 2] to remove bubbles from the hydraulic system of the autoanalyzer according to claim 2, before the fluid flow enters the colorimeter cell, including an input 16 for the total liquid flow with air bubbles, an exit 17 for removing air bubbles, an exit 18 for introducing liquid without air bubbles into the colorimeter cell a separation chamber 19, characterized in that the inlet 16 for the total fluid flow with air bubbles, the outlet 17 for removing air bubbles, the outlet 18 for introducing liquid without air bubbles into the colorimeter cuvette provides a vertical ln liquid flows, while the outlet 17 for removing air bubbles is connected to an additional channel of the peristaltic pump and has greater productivity than the channel for introducing liquid without air bubbles into the colorimeter cell; the volume of the separation chamber 19 of the bubble separator [Fig. 2] is determined by the volume of carbon dioxide released and is ensured by the ratio of the productivity of the hydraulic channel of the selected soil extraction sample and the hydraulic feed channel of the staining reagent, thereby ensuring reliable removal of air bubbles from the hydraulic stream before it enters the colorimeter cell, which improves the quality of analysis

The technology of automated direct measurement of the concentration of mobile mineral forms of phosphorus in soil samples when it is extracted by carbon ammonium extraction by the proposed method and devices providing this technology.

Analytical preparation for the analysis is carried out according to OST 10 256-2000.

Further, according to the equipment operation manual, a hydraulic circuit is assembled, as shown in FIG. one.

Then, a cassette with calibration solutions is installed on the sample feeder and both channels are graduated using a coloring reagent to determine phosphorus.

After calibrating both channels using a coloring reagent in one of the channels, the coloring reagent is replaced with a non-staining reagent.

Having achieved a stable baseline (zero signal) on the monitor screen, the measurements of the test samples begin. The measurement results obtained in the channel with a non-staining reagent determine the amount of correction that must be subtracted from the measurement result of the same sample in the staining channel. Autoanalyzer software performs this operation automatically.

Claims (3)

1. A method for automated direct determination of phosphorus available to plants in a carbon ammonium soil extract stained with humic compounds, namely, that the obtained extract sample is analyzed on a flow-type autoanalyzer with spectrophotometric termination and measurement of the optical density of hydraulic flows in the spectral range of 898-900 nm, characterized in that simultaneous two-channel spectrophotometry of one sample is performed: in one channel with the addition of reagents for staining I have phosphorus, and in another channel with the addition of reagents without staining phosphorus, the automated calculation of the difference in the results of the two channels determines the content of phosphorus available to plants, excluding phosphorus, which is part of the organic component of the extract and not available to plants; the difference in the optical density measurements of the same sample in two channels characterizes the phosphorus content available to plants, excluding phosphorus, which is part of the organic component of the extract and not available to plants. 2. An autoanalyzer for the direct determination of phosphorus available to plants in a soil extract stained with humic compounds, including a bubble separator for removing bubbles from the hydraulic system before the fluid flow enters the colorimeter cuvette and consisting of a sample feeding machine, a tank with distilled water, a hydraulic system with mixers, thermostats , cooling devices, spectrophotometers, a collector, and a computer system, characterized in that the auto-analyzer includes a sample separator and the two channels and the multichannel peristaltic pump, a hydraulic system comprises two spectrophotometer in which simultaneously a measured drawing a sample and which allows detection of sample absorbance over a single channel with the addition of reagents for staining phosphorus, and the other channel with the addition of reagents without staining phosphorus. 3. A bubble separator for removing bubbles from the hydraulic system of the autoanalyzer according to claim 2, before the fluid flow enters the colorimeter cuvette, including an entrance for a common liquid flow with air bubbles, an outlet for removing air bubbles, an outlet for introducing liquid without air bubbles into the colorimeter cuvette, dividing chamber, characterized in that the inlet for the total fluid flow with air bubbles, the outlet for removing air bubbles, the outlet for introducing liquid without air bubbles into the colorimeter cell vertical fluid flows, while the outlet for removing air bubbles is connected to an additional channel of the peristaltic pump.

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