CS254779B1 - Semi-quantitative determination of nitrate and nitrite content in plants - Google Patents

Abstract

Semi-quantitative determination of nitrate and nitrite content in plants consists in homogenizing the liquid pressed from the plant in a weight ratio of 1:4 to 6 by rubbing with a powder reagent mixture containing zinc or manganese sulfate in an amount of 2 to 8.5 parts by weight, sulfonic acid in an amount of 1 to 3 parts by weight, naphthylamine in an amount of 0.5 to 1.5 parts by weight, organic acids, e.g. citric or tartaric acid in an amount of 30 to 50 parts by weight and fillers such as barium sulfate, calcium sulfate, silica gel or a mixture thereof, in an amount of 50 to 130 parts by weight and after 5 to 30 minutes the color of the mixture is compared with a color scale expressing the nitrogen content in the form of nitrates contained in the examined liquid.

Description

The invention relates to a semi-quantitative determination of nitrate and nitrite content in plants, which is directly applicable in agricultural operations in the field without the need for laboratory equipment.

The determination methods used so far require laboratory and instrumentation equipment. The most common are colorimetric determinations in solution, which are, however, labor-intensive. The determination procedure cannot be simplified so that it can be used by ordinary agricultural workers directly in the field.

The most common indicative methods for determining nitrate in field conditions are most often based on the reaction with diphenylamine /diphenylbenzidine/ in a concentrated sulfuric acid environment. When working with such a reagent, the worker is splashed, resulting in burns, damage to clothing, etc. The color reaction with nitrate is unstable, the coloration is uneven, and therefore the quantification of the test result is problematic.

There are also various forms of indicator papers in the world, but they are difficult to obtain and also expensive. The resolution is insufficient, the stability of the reagent mixture of the indicator paper is limited, and the intensity of the surface color is uneven.

The above disadvantages are eliminated by the method of semi-quantitative determination of nitrate and nitrite content in plants according to the invention, which consists in homogenizing the liquid pressed from the plant in a weight ratio of 1:4 to 6 by rubbing with a powder reagent mixture containing zinc, manganese sulfate as reducing agents in an amount of 2 to 8.5 parts by weight, sulfanilic acid in an amount of 1 to 3 parts by weight, β-naphthylamine in an amount of 0.5 to

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- 2 1.5 parts by weight, organic acids, for example citric or tartaric acid in an amount of 30 to 50 parts by weight and fillers such as barium sulfate, calcium sulfate, silica gel or a mixture thereof in an amount of 50 to 130 parts by weight and after 5 to 30 minutes the colour of the mixture is compared with a colour scale expressing the content of nitrogen in the form of nitrates contained in the liquid under examination.

The proposed method has a number of advantages. The proposed method uses a solid reaction mixture, which ensures the reduction of nitrates to nitrites, which is of practical importance. Nitrites are more toxic to animal organisms than nitrates. Volumetric measurement of a solid reaction mixture is simpler than liquid. The range of color changes of the reagent well reflects practically significant values of nitrate content in plant production /forage/ for the needs of agricultural operation managers. The necessary chemicals for preparing the mixture are easily available and relatively inexpensive. The actual preparation of the reagent mixture is simple and fast. It can be prepared operationally immediately before the actual testing season in the necessary quantity. Simple methods of measuring the reagent mixture and the tested juice /calibrated measuring cup, dropper/ are used, which ensure the necessary accuracy of determining the concentration of nitrates and nitrites. Unlike test papers, uniform surface coloration is achieved by mixing the reagent mixture with the juice, which increases objectivity in assessing the coloration. By modeling the composition of the reagent mixture and its weight ratio to the tested liquid, while maintaining the condition of a well-mixable paste, the color intensity can be changed, and thus the resolution ability in the required range of nitrate and nitrite concentrations in the liquid.

The determination is simple and sufficiently sensitive, and can be carried out with minimal equipment directly by agricultural and technical staff, so that they can promptly exclude defective forage from feeding, thereby preventing a possible threat to the health of or reduction in the productivity of farm animals. It eliminates the time-consuming determination, that is, starting from

-5 254 779 by transporting the sample to an equipped chemical laboratory and ending with the return delivery of the analysis result to the agricultural operation manager. The speed and sensitivity of the test immediately provides sufficient argumentation for the correct decision-making of the agricultural operation manager.

The method of determination is illustrated in the following examples.

Example 1

To perform the test you will need:

- Droplet analysis plate.

- Measuring cup ^reagent mixture /0.2 g/, available in fishing supplies /punch for cutting out bait/.

- Set of standards /50, 100, 200, 500, 500 and 750 mg N-NO5.I“ ¹ /. The basic standard /1000 mg N-NO5.I“ ¹ / is prepared by weighing the dried chemical KNO5 or NaNOj /7.2214 g KNO5.I“ ¹ or 6.0681 g NaNO^.l“^·/. Note - The expediency of the determination is increased by replacing the standards with an equivalent color scale corresponding to the colored standards.

- Fine metal spatula.

- Eye dropper.

- Plant press /you can use a vegetable press manufactured by the regional service company Tišnov /Pozořice/ with minimal modification, covering the perforated bottom with a sheet of Al-foil.

- Hourglasses.

- A container for distilled water.

- Filter paper or cellulose wadding to clean equipment.

- Reaction mixture of parts by weight of manganese sulfate /T.toSO^.4 H2O/ — parts by weight of zinc powder /Zn/ parts by weight of sulfenic acid /CgHyO^NS/

0.8 parts by weight of 06-naphthylamine /C1QH9N/ parts by weight of calcium sulfate /CaSO4.2 H2O/ parts by weight of Kieselguhr G /silica gel with 10% gypsum/ parts by weight of citric acid are thoroughly mixed by rubbing in a large mortar /minimum top diameter 25 cm/. The reagent mixture should be stored in a dark container.

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The liquid from the plant material sample is squeezed onto a watch glass. 0.2 g of solid reagent mixture is measured onto the test plate (full, leveled fish measuring cup). One drop of the test liquid is added to the reagent mixture using an eye dropper and mixed with a spatula. After five minutes, it is compared with similarly prepared standards or a color scale.

Result evaluation:

The interpretation of the determination result depends on the dry matter content of the tested plant material. The dry matter content of fresh plants is a relatively stable quantity that depends on the plant species and the physiological age of the plant, the values are commonly known.

Table transferring results to contents N-NO^ in dry matter % of dry matter of the tested plant sample Standard values /mg N- 50 100 2Ó0 -NO5.I” ¹ / 500 500 750 N- content equivalence -NO3 in dry matter /%/ « 6 0.084 0.167 0.554 0.501 0.855 1,252 θ 0.065 0.125 0.250 0.575 0.625 0.958 10 0.050 0.100 0.200 0.500 0.500 0.750 12 0.042 0.085 0.166 0.249 0.415 0.622 14 0.056 0.071 0.142 0.215 0.555 0.555 16 0.051 0.06 0.125 0.187 0.512 0.469 18 0.027 0.059 0.111 0.166 0.277 0.416 20 .0.025 0.050 0.100 0.150 0.250 0.575 22 0.025 0.045 0.091 0.156 0.227 0.540 24 0.021 0.042 0.085 0.125 0.209 0.515 26 0.019 0.058 0.077 0.115 0.192 0>289 28 0.018 0.056 0.071 0.107 0.178 0.268 50 0.017 0.055 0.066 0.099 0.166 0.250

*

Visually clearly distinguishable colors are between these standard values: 50 100 200 500 500 750, where the color intensity increases from pale pink, pink, deep pink, red to red-violet. For ordinary fresh forage, a signal of unsuitable forage for feeding is a dark red - purple color.

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The content of nitrogen in the form of nitrates and nitrites was determined on fresh hay oats from a field trial with different nitrogen fertilization intensities. By semi-quantitative determination according to the invention, the sample showed a color corresponding to a concentration of less than 100 ppm in the juice. After conversion to a dry matter of 24% by weight, this test determined a concentration of N-NO3 of less than 0.04% by weight in the oat sample.

In the laboratory, the same sample was determined by the laboratory determination of nitrate according to the method CAIAW0, D.A. - HAROON, M. - SCHRADER, L.E. - Y0UNG9, U.L.: Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid. Comm. Soil Sci. Plant Anal. Vol. 6, No 1., 71, 1975, and 0.055% by weight N-NO5 was found.

Samples 2 and 5 of haylage oats were processed in a similar manner. A semiquantitative test revealed a N-NO3 concentration in the juice of sample 2 of less than 200 ppm, which, at a dry matter content of 24% by weight, is less than 0.08% N-NO3 in oats. A laboratory method determined 0.065% by weight N-NO3.

In sample 5, the concentration of N-NO3 in the juice was higher than 500 ppm, which, when converted to a dry matter of 24% by weight, is more than 0.21% of N-NO3 in oats. The laboratory method determined 0.264% of N-NO3 in oats.

Example 2 · ' . in ..

The ryegrass was tested. One drop of the pressed liquid was homogenized on a test plate with 0.25 S of the reagent mixture. After 10 minutes, the color was compared with similarly prepared color standards. The reaction mixture contained 5 wt. parts of manganese sulfate, 1 wt. part of zinc, 2 wt. parts of sulphanilic acid, 0.7 wt. parts of oC-naphthylamine, 45 wt. parts of calcium sulfate and 45 wt. parts of tartaric acid. The N-NO3 content of the juice ranged from 50 to 500 ppm. At a dry matter of 20 wt. %, the N-NO3 content in the plant ranged from 0.025 to 0.575 wt. %.

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The N-NO3 content in lettuce was monitored in the same way, in which the juice contained 50 to 300 ppm N-NO^. At 6% wt. dry matter, the N-NO3 content in lettuce ranged from 0.08 to 0.50% wt. Ν-ΝΌ3.

In carrot juice, the content of N-NO3 varied from 50 to 200 ppm. At 14% dry matter, the content of N-NO3 ⁱⁿ the juice varied from 0.04 to 0.14% by weight.

Claims (1)

Semi-quantitative determination of nitrate and nitrite content in plants, characterized in that the fluid extracted from the plant is homogenized by friction in a 1: 4 to 6 weight ratio with a powder reagent composition containing zinc or manganese sulphate in an amount of 2 to 8.5% by weight. % sulfanilic acid in an amount of 1 to 3 wt. 0.5 parts by weight of naphthylamine 1.5 wt. % of an organic acid such as citric or tartaric acid in an amount of 30 to 50 wt. parts and fillers such as barium sulfate, calcium sulfate, silica gel or a mixture thereof in an amount of 50 to 130 wt. After 5 to 30 minutes, the color of the mixture is compared to a color scale expressing the nitrogen content in the form of the nitrates contained in the test liquid. Printed by Moravian Printing Works, '