RU2045067C1 - Express method for determining content of nitrates in plants - Google Patents

Abstract

FIELD: agriculture. SUBSTANCE: this method includes such steps as preparation of sample, measurement of potential of nitrate ion-selective electrode and determination of content of nitrate in sample based on electrode potential measurement results. This method prescribes preparing sample by squeezing freshly taken samples of vegetable stock and treating resultant juice with 1-percent aqueous solution of potassium alum (1 28 to 30 volume ratio) with stirring. EFFECT: greater simplicity and speediness plus applicability in field conditions. 1 tbl

Description

 The invention relates to agriculture and can be used in the diagnosis of plant nutrition in the growing process, as well as in the quality control of agricultural products.

 A known method for the determination of nitrate nitrogen in plants with disulfophenolic acid. The method involves preparing a sample, treating it with disulfophenolic acid, and then with an alkali solution. In the presence of nitrates, a yellow color appears in the test solution. Then, the optical density of the solution is determined in a photoelectrocolorimeter, and the concentration of nitrates in the solution is determined on the basis of their optical density according to the calibration curve (Workshop on Agrochemistry. Edited by Prof. B. Yagodin, M. VO "Agropromizdat, 1987, p. 186 -188).

 The method has high accuracy and gives stable results. However, it is time consuming, time consuming and can only be used in laboratory conditions.

 There is also a method for determining the amount of nitrates in fruits, including sampling, grinding, extraction of nitrates with acetic acid, introducing salicylic and sulfuric acids into the extract, and then an alkali solution, measuring the optical density of the resulting mixture and then establishing the measured value of the amount of nitrates (Copyright USSR certificate N 1160302, class G 01 N 31/04, publ. 1985).

 However, this method is also complex and time-consuming to perform and cannot be used for operational diagnostics of the availability of plants in the process of growing with nitrogen and quality control of agricultural products.

 Closest to the proposed is a widely used in the practice of agrochemical research method for determining nitrate nitrogen in plant products using an ion-selective electrode. The method involves preparing a sample by grinding plant material, taking an average sample and homogenizing it in a 1% aqueous solution of potassium alum. In the absence of a homogenizer, a sample of the crushed plant material is ground in a mortar with quartz sand to a homogeneous mass, the sand being pre-insisted in hydrochloric acid, then chlorine ions are washed, dried and calcined in a muffle furnace. The pounded sample is poured with a 1% aqueous solution of alum-potassium alum and re-triturated for 3-5 minutes. The resulting mass is quantitatively transferred into a glass and vigorously mixed. In the resulting suspension, the potential of the nitrate ion-selective electrode is measured, and the concentration of nitrates in the test suspension is found according to the calibration graph based on the measured material (Workshop on agrochemicals. Edited by Prof. B. Yagodin, M. VO Agropromizdat, 1987, p. 188-190).

 The method allows to determine with quite high accuracy the content of nitrate nitrogen in the plant material and for less time than the method with disulfophenolic acid. However, it requires sophisticated equipment, it is applicable only in stationary laboratory conditions, and in the absence of a homogenizer in the laboratory, the method is further complicated due to the complexity and duration of the homogenate preparation process.

 The aim of the invention is to simplify and accelerate the method, ensuring its applicability in the field for operational diagnostics of plant nutrition during the cultivation and quality control of agricultural products.

 This goal is achieved by the fact that in the proposed method for determining nitrate nitrogen in plants, including sample preparation, measuring the potential of a nitrate ion selective electrode and determining the concentration of nitrate nitrogen in the test sample based on the measured potential, according to the invention, the sample is prepared by squeezing the juice from freshly selected samples of plant material and processing it with a 1% aqueous solution of alum-potassium alum with a volume ratio of 1: 28-30 and with stirring and.

 In the proposed method, the process of sample preparation is greatly simplified and accelerated, which allows its use not only in laboratory conditions, but also in field studies. It was found that the proposed conditions for sample preparation eliminate the effect of interfering ions on the electrode function of the ion-selective electrode to a lesser extent, as in the known method. This makes it possible to obtain no less reliable and accurate analysis results.

 PRI me R. From 80-100 plants taken diagonally in the morning hours, 20-30 healthy plants are selected for analysis. Selected plant samples are wiped with cotton or filter paper, placed in a hand press and squeezed juice. If the juice is squeezed poorly, then it is necessary to turn the mass in the press and again squeeze the levers. Squeezed juice is poured into a small test tube or glass. Then, 0.5 ml of juice is taken with a pipette (18-19 drops, transferred to a 25 ml graduated cylinder, a 1% aqueous solution of alum-potassium alum is poured to a mark of 15 ml (volume ratio of juice and solution 1:29), mixed, poured into 50 ml beaker and measure the potential of a nitrate ion-selective electrode on an ionomer.

, где рNO₃ отрицательный логарифм концентрации нитратного азота;
14 атомная масса азота;
V объем вытяжки, мл;
V₁ объем сока, мл;
10³ коэффициент перевода в мл.When conducting analysis in the laboratory and using an ionomer of the type EV-74, the content of nitrate nitrogen in the plant material in mg / l of juice is found by the formula
X

where pNO _{3 is the} negative logarithm of the concentration of nitrate nitrogen;
14 atomic mass of nitrogen;
V volume of the extract, ml;
V ₁ juice volume, ml;
10 ³ conversion rate in ml.

When conducting an analysis in the field, it is necessary to use a NM-002 type nitrate meter. It is calibrated to determine nitrate nitrogen in mg / L. Before determining nitrates, the device is adjusted according to standard solutions. As a solution of C ₁ , a solution with pCNO ₃ 5 and a conversion factor of 42 should be used. As a solution of C ₂ , a solution with pCNO ₃ 2.5 and a conversion factor of 1328 should be used. As a solution of C ₃ , a solution with pCNO ₃ 3 and a conversion factor should be used. coefficient 420. As solution C ₄ , a solution with pCNO ₃ 4 and conversion factor 42 should be used.

 The results of specific determinations on various plants obtained in the field and statistical processing of experimental data are given in the table.

 The results obtained allow us to conclude that the proposed method reduces the variation of the measurement results and slightly increases the accuracy of determination. The correlation between the known and proposed methods is strong. The correlation coefficient is 0.79.

Claims (1)

 EXPRESS METHOD FOR DETERMINING NITRATE NITROGEN IN PLANTS, including preparing a sample, measuring the potential of a nitrate ion selective electrode and determining the concentration of nitrate nitrogen in the test sample based on the measured potential, characterized in that the sample is prepared by squeezing the juice from freshly selected samples of plant material and processing its 1% aqueous solution of alum-potassium alum with a volume ratio of 1: 28-30 and with stirring.

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