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Chemical analysis of plants. Agrochemical analysis of soils, plants, fertilizers The first methods of chemical analysis of plants were developed

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Introduction

1. Soil analysis

2. Plant analysis

3. Fertilizer analysis

Conclusion

Bibliography

Introduction

Agronomic chemistry studies Ch. arr. questions of nitrogen and mineral nutrition of page - x. plants in order to increase yield and improve production. Thus, a. X. explores the composition of page - x. plants, soil, fertilizers and processes of their mutual influence. In the same way, she studies the processes for preparing fertilizers and substances used to control pests, and also develops chemical methods. analysis of agronomic objects: soil, plants and products obtained from them, etc. The microbiological processes of the soil are especially significant. In this area a. X. in contact with soil science and general agriculture. On the other hand, a. X. relies on plant physiology and is in contact with it, since a. X. deals with the study of processes occurring during germination, nutrition, seed maturation, etc., and uses the methods of water, sand and soil cultures. In their research, agronomists-chemists, using Ch. arr. chem. methods, of which physicochemical methods have been especially widely used in recent times, at the same time they must master the methods of artificial cultures and bacteriological research methods. Due to the complexity and diversity of tasks a. x., some groups of questions that were previously included in a. x., stood out in independent disciplines.

This applies to chemistry, which studies the chemical composition of plants, mainly page - x. and technical, as well as biological chemistry and biological physics, which study the processes of a living cell.

1 . Analysissoil

Features of the soil as an object chemical research and indicators of the chemical state of soils

Soil is a complex object of study. The complexity of studying the chemical state of soils is due to the peculiarities of their chemical properties and is associated with the need to obtain information that adequately reflects the properties of soils and provides the most rational solution to both theoretical issues of soil science and issues of practical use of soils. A wide range of indicators is used to quantitatively describe the chemical state of soils. It includes indicators determined in the analysis of almost any objects and developed specifically for soil research (exchangeable and hydrolytic acidity, indicators of the group and fractional composition of humus, the degree of saturation of soils with bases, etc.)

The features of the soil as a chemical system are heterogeneity, polychemistry, dispersity, heterogeneity, change and dynamics of properties, buffering, as well as the need to optimize soil properties.

Soil polychemistry. In soils, the same chemical element can be part of various compounds: easily soluble salts, complex aluminosilicates, and organomineral substances. These components have different properties, on which, in particular, the ability of a chemical element to pass from the solid phases of the soil to the liquid one, migrate in the soil profile and in the landscape, be consumed by plants, etc. depends. Therefore, in the chemical analysis of soils, not only the total content of chemical elements is determined, but also indicators characterizing the composition and content of individual chemical compounds or groups of compounds with similar properties.

Soil heterogeneity. Soil consists of solid, liquid and gaseous phases. When studying the chemical state of the soil and its individual components, indicators are determined that characterize not only the soil as a whole, but also its individual phases. Mathematical models have been developed to assess the relationship between the levels of partial pressure of carbon dioxide in soil air, pH, carbonate alkalinity, and calcium concentration in soil solution.

Soil polydispersity. The solid phases of the soil consist of particles of different sizes from grains of sand to colloidal particles with a diameter of several micrometers. They are different in composition and have different properties. In special studies of the genesis of soils, indicators of the chemical composition and other properties of individual granulometric fractions are determined. The dispersity of soils is associated with their ability to ion exchange, which, in turn, is characterized by a specific set of indicators - the capacity of cation and anion exchange, the composition of exchangeable cations, etc. Many chemical and physical properties soils.

Acid-base and redox properties of soils. The composition of soils includes components that exhibit properties acids and bases, oxidizing and reducing agents. At solving various theoretical and applied problems soil science, agrochemistry, land reclamation determine indicators, characterizing the acidity and alkalinity of soils, their redox state.

Heterogeneity, variability, dynamics, buffering of chemical properties of soils. Soil properties vary even within the same genetic horizon. When researching soil profile formation processes are assessed chemical properties of individual elements of soil organization masses. Soil properties vary in space, change in time and at the same time, soils have the ability resist changes in their properties, i.e. they show buffering. Indicators and methods for characterizing variability have been developed, dynamics, buffer properties of soils.

Changes in soil properties. Various processes continuously occur in soils, which lead to changes in the chemical properties of soils. Practical use find indicators that characterize the direction, severity, speed of processes occurring in soils; the dynamics of changes in soil properties and their regimes are studied. Variation in quality of soil composition. Different types and even types and varieties of soils can have such different properties that not only different analytical methods, but also different sets of indicators are used to characterize them chemically. So, in podzolic, soddy-podzolic, gray forest soils, the pH of aqueous and salt suspensions, exchangeable and hydrolytic acidity are determined, exchangeable bases are displaced from soils by aqueous solutions of salts. When analyzing saline soils, the pH of only aqueous suspensions is determined, and instead of acidity indicators, total, carbonate and other types of alkalinity are determined. The listed features of soils largely determine the fundamental principles of methods for studying the chemical state of soils, the nomenclature and classification of indicators of the chemical properties of soils and chemical soil processes.

System of indicators of the chemical state of soils

Group 1. Indicators of soil properties and soil components

Subgroups:

1. Indicators of soil composition and soil components;

2. Indicators of the mobility of chemical elements in soils;

3. Indicators of acid-base properties of soils;

4. Indicators of ion-exchange and colloid-chemical properties of soils;

5. Indicators of redox properties of soils;

6. Indicators of catalytic properties of soils;

Group 2. Indicators of chemical soil processes

Subgroups:

1. Indicators of the direction and severity of the process;

2. Process speed indicators.

Principles for determining and interpreting indicator levels

The results of soil analysis contain information about soil properties and soil processes and, on this basis, make it possible to solve the problem facing the researcher. Techniques for interpreting the levels of indicators depend on the methods for their determination. These methods can be divided into two groups. The methods of the first group make it possible to evaluate its properties without changing the chemical state of the soil. The second group - methods based on the chemical treatment of the analyzed soil sample. The purpose of this treatment is to reproduce the chemical equilibria that occur in real soil or deliberately disrupt the relationships that have developed in soils and extract a component from the soil, the amount of which makes it possible to evaluate the chemical property of the soil or the process taking place in it. This stage of the analytical process - the chemical treatment of a sample of soil - reflects the main feature of the research method and determines the methods for interpreting the levels of most of the indicators being determined.

Preparation of soil samples from the studied areas

Soil samples should be taken using cores with a diameter of about 10 mm to a depth of 10-20 cm. It is better to pre-sterilize the cores in boiling water (100 0 C). For soil analysis, mixed soil samples are taken to the depth of the cultivated layer. As a rule, it is sufficient to make one mixed sample for a plot of up to 2 ha. A mixed sample is made up of 15-20 individual soil samples taken evenly over the entire area of ​​the site. Samples for soil analysis are not taken immediately after the introduction of mineral and organic fertilizers, notice. Each mixed sample weighing 500 g is packed in a cloth or plastic bag and labelled.

Soil preparation for agrochemical analysis

Compilation of an analytical sample is a responsible operation that ensures the reliability of the results obtained. Negligence and errors in the preparation of samples and taking the average sample are not compensated for by subsequent qualitative analytical work. Soil samples taken in the field or in the growing house are pre-dried in air at room temperature. Storage of raw samples leads to significant changes in their properties and composition, especially as a result of enzymatic and microbiological processes. On the contrary, temperature overheating is accompanied by a change in the mobility and solubility of many compounds.

If there are many samples, then drying is carried out in cabinets with forced ventilation. Determination of nitrates, nitrites, absorbed ammonium, water-soluble forms of potassium, phosphorus, etc. carried out on the day of sampling at their natural humidity. The remaining determinations are carried out in air-dry samples. Dry samples are ground in a soil mill or ground in a porcelain mortar with a rubber-tipped pestle. The ground and dried sample is passed through a sieve with a hole diameter of 2-3 mm. Grinding and sifting is carried out until the entire sample taken has passed through the sieve. It is allowed to discard only fragments of stones, large roots and foreign inclusions. Samples are stored in closed craft bags in a room where there are no chemicals. A sample of soil for analysis is taken by the “average sample” method. To do this, the sifted sample is scattered in a thin layer (about 0.5 cm) on a sheet of paper in the form of a square and divided with a spatula into small squares with a side of 2-2.5 cm. A part of the sample is taken from each square with a spatula.

The main agrochemical indicators of soil analysis, without which not a single cultivation of land can do, are the content of humus, mobile forms of phosphorus, nitrogen and potassium, soil acidity, the content of calcium, magnesium, as well as trace elements, including heavy metals. Modern methods of analysis make it possible to determine 15-20 elements in one sample. Phosphorus is a macronutrient. According to the availability of mobile phosphates, soils are distinguished with a very low content - less than a mg., Low - less than 8 mg., Medium - 8 - 15 mg. and high - more than 15 mg. phosphates per 100 g of soil. Potassium. For this element, gradations have been developed according to the content of mobile forms in the soil: very low - up to 4 mg, low - 4-8 mg, medium - 8-12 mg, high - 12-17 mg, high - more than 17 mg. exchangeable potassium per 100 g of soil. Soil acidity - characterizes the content of hydrogen protons in the soil. This indicator is expressed by the pH value.

Soil acidity affects plants not only through the direct effect of toxic hydrogen protons and aluminum ions on plant roots, but also through the nature of the intake of nutrients. Aluminum cations can bind with phosphoric acid, converting phosphorus into a form inaccessible to plants.

The negative effect of low acidity is reflected in the soil itself. When hydrogen protons are displaced from the soil absorbing complex (SAC) of calcium and magnesium cations, which stabilize the soil structure, the soil granules are destroyed and its structure is lost.

Distinguish between actual and potential soil acidity. The actual acidity of the soil is due to the excess concentration of hydrogen protons over hydroxyl ions in the soil solution. The potential acidity of the soil includes hydrogen protons bound to the AUC. To judge the potential acidity of the soil, the pH of the salt extract (pH KCl) is determined. Depending on the pH KCl value, soil acidity is distinguished: up to 4 - very strongly acidic, 4.1-4.5 - strongly acidic, 4.6-5.0 - medium acidic, 5.1-5.5 - slightly acidic, 5.6- 6.0 is close to neutral and 6.0 is neutral.

Soil analysis for heavy metals and radiation analysis are classified as rare analyses.

Receipt water solution soils.

Solutions of substances contained in the soil are obtained in many ways, which can be fundamentally divided into two groups: - obtaining a soil solution; - obtaining an aqueous extract from the soil. In the first case, unbound or weakly bound soil moisture is obtained - that which is contained between soil particles and in soil capillaries. This is a slightly saturated solution, but its chemical composition is relevant for the plant, since it is this moisture that washes the roots of plants and it is in it that the exchange of chemicals takes place. In the second case, soluble chemical compounds associated with its particles are washed out of the soil. The yield of salt into the water extract depends on the ratio of soil and solution and increases with an increase in the temperature of the extracting solution (up to certain limits, since too high a temperature can destroy any substances or transfer them to a different state) and an increase in the volume of the solution and the degree of soil refinement ( up to certain limits, since too fine dusty particles can make it difficult or impossible to extract and filter the solution).

The soil solution is obtained using a number of tools: pressing, centrifugation, displacement of an immiscible liquid solution, vacuum filtration method and lysimetric method.

Pressurization is carried out with a soil sample taken from the field to the laboratory. The more solution needed, the larger the sample or the higher the applied pressure, or both.

Centrifugation is carried out at 60 rpm for a long time. The method is inefficient, and is suitable for soil samples with moisture close to the full possible moisture content of the given soil. For dry soil, this method is not applicable.

The displacement of soil moisture by a substance immiscible with the soil solution makes it possible to obtain virtually all soil moisture, including capillary moisture, without the use of complex equipment. Alcohol or glycerin is used as a displacement fluid. The inconvenience is that these substances, in addition to their high density, have a good extracting ability with respect to some compounds (for example, alcohol easily extracts soil organic matter), so it is possible to obtain overestimated values ​​for the content of a number of substances compared to their actual content in the soil solution. The method is not suitable for all soil types.

With the vacuum filtration method, a vacuum is created above the sample with the help of vacuum, which exceeds the level of soil moisture tension. In this case, capillary moisture is not extracted, since the tension forces in the capillary are higher than the tension forces of the free liquid surface.

The lysimetric method is used in the field. The lysimetric method allows not so much to estimate the gravitational moisture (that is, moisture capable of moving through the soil layers due to the force of gravity - with the exception of capillary moisture), but to compare the content and migration of chemical elements of the soil solution. Free soil moisture is filtered through the thickness of the soil horizon by gravitational forces to a sampler located on the soil surface.

To obtain a more complete picture of the chemical composition of the soil, a soil extract is prepared. To obtain it, a soil sample is crushed, passed through a sieve with cells with a diameter of 1 mm, water is added in a mass ratio of 1 part of soil to 5 parts of bidistilled (purified from any impurities, degassed and deionized) water, pH 6.6 - 6.8, temperature 20 0 C. Degassing is carried out in order to free water from impurities of dissolved gaseous carbon dioxide, which, when combined with certain substances, gives an insoluble precipitate, reducing the accuracy of the experiment. Impurities of other gases can also have a negative effect on the results of the experiment.

For more accurate weighing of a sample, one should take into account its natural humidity, field (for a freshly taken sample) or hygroscopic (for a dried and stored sample). Determined as a percentage of the mass of the sample, its moisture content is converted into mass and summed up with the required mass. The sample is placed in a dry flask with a volume of 500-750 ml, water is added. The flask with the soil sample and water is tightly stoppered and shaken for two to three minutes. Next, the resulting solution is filtered through an ashless paper pleated filter. It is important that there are no volatile vapors of acids in the room (it is preferable to carry out work under draft, where acid solutions are not stored). Before filtering, the soil solution is shaken well so that small soil particles close the largest pores of the filter and the filtrate is more transparent. Approximately 10 ml of the initial filtrate is discarded as it contains impurities from the filter. Filtering the rest of the primary filtrate is repeated several times. Work on determining the content of chemicals in the aqueous extract is started immediately after it is obtained, since over time chemical processes occur that change the alkalinity of the solution, its oxidizability, etc. Already the filtration rate can show the relative total salt content in the solution. If the water extract is rich in salts, then the filtration will take place quickly and the solution will turn out to be transparent, since the salts prevent the peptization of soil colloids. If the solution is poor in salts, the filtration will be slow and not of very high quality. In this case, it makes sense to filter the solution several times, despite the low speed, because. with additional filtration, the quality of the water extract increases due to a decrease in the content of soil particles in it.

Methods for quantitative analysis of extracts or any other solutions obtained during the analysis of soils.

In most cases, the interpretation of soil analysis results does not depend on the measurement method. In the chemical analysis of soils, almost any of the methods available to analysts can be used. In this case, either the directly desired value of the indicator is measured, or the value that is functionally related to it. The main sections of chem. soil analysis: gross, or elemental, analysis - allows you to find out the total content of C, N, Si, Al, Fe, Ca, Mg, P, S, K, Na, Mn, Ti and other elements in the soil; analysis of water extract (the basis for the study of saline soils) - gives an idea of ​​the content of water-soluble substances in the soil (sulfates, chlorides and carbonates of calcium, magnesium, sodium, etc.); determination of the absorptive capacity of the soil; identification of the provision of soils with nutrients - they establish the amount of easily soluble (mobile) compounds of nitrogen, phosphorus, potassium, etc. absorbed by plants. Much attention is paid to the study of the fractional composition of soil organic substances, the forms of compounds of the main soil components, including trace elements.

In the laboratory practice of soil analysis, classical chemical and instrumental methods are used. With classical chemical methods, the most accurate results can be obtained. The relative error of determination is 0.1-0.2%. The error of most instrumental methods is much higher - 2-5%

Among the instrumental methods in soil analysis, electrochemical and spectroscopic methods are most widely used. Among electrochemical methods, potentiometric, conductometric, coulometric and voltammetric methods are used, including all modern varieties polarography.

To assess the soil, the results of the analyzes are compared with the optimal levels of the content of elements established experimentally for a given type of soil and tested under production conditions, or with the data available in the literature on the provision of soils with macro- and microelements, or with the MPC of the studied elements in the soil. After that, a conclusion is made about the state of the soil, recommendations are given for its use, doses of ameliorants, mineral and organic fertilizers for the planned crop are calculated.

When choosing a measurement method, the characteristics of the chemical properties of the analyzed soil, the nature of the indicator, the required accuracy of determining its level, the possibilities of measurement methods, and the feasibility of the required measurements under the conditions of the experiment are taken into account. In turn, the accuracy of measurements is determined by the purpose of the study and the natural variability of the studied property. Accuracy -- a collective characteristic of the method, evaluating the correctness and reproducibility of the results of the analysis.

The ratio of levels of content in soils of some chemical elements.

Different levels of content and different chemical properties of the elements do not always make it appropriate to use the same measurement method for the quantitative determination of the entire required set of elements.

In the elemental (gross) analysis of soils, methods with different detection limits are used. To determine the chemical elements, the content of which exceeds tenths of a percent, it is possible to use classical methods of chemical analysis - gravimetric and titrimetric.

Different properties of chemical elements, different levels of their content, the need to determine different indicators of the chemical state of the element in the soil make it necessary to use measurement methods with different detection limits.

Soil acidity

Determining the reaction of soils is one of the most common analyzes, both in theoretical and applied research. The most complete picture of the acidic and basic properties of soils is formed by the simultaneous measurement of several indicators, including titratable acidity or alkalinity - the capacity factor and the pH value - the intensity factor. The capacity factor characterizes the total content of acids or bases in soils; the buffer capacity of soils, the stability of the reaction over time and in relation to external influences depend on it. The intensity factor characterizes the strength of the instant action of acids or bases on the soil and plants; the flow of minerals into plants in a given period of time depends on it. This allows a more correct assessment of soil acidity, since in this case the total amount of hydrogen and aluminum ions in the soil in free and absorbed states is taken into account. Actual acidity (pH) is determined potentiometrically. Potential acidity is determined by converting hydrogen and aluminum ions into a solution when cultivating the soil with an excess of neutral salts (KCl):

The exchange acidity of the soil is judged by the amount of free hydrochloric acid formed. Part of the H + ions remains in the absorbed state (strong HCl formed as a result of p-ii completely dissociates and an excess of free H + in the solution prevents their complete displacement from the FPC). The less mobile part of the H + ions can be transferred into solution only with further soil treatment with solutions of hydrolytically alkaline salts (CH 3 COONa).

The hydrolytic acidity of soils is judged by the amount of free acetic acid formed. In this case, hydrogen ions most completely pass into the solution (are displaced from the PPC), because the resulting acetic acid strongly binds hydrogen ions, and the reaction shifts to the right until the complete displacement of hydrogen ions from the FPC. The value of hydrolytic acidity is equal to the difference between the results obtained by tillage with CH 3 COONa and KCl. In practice, the value of hydrolytic acidity is taken as the result obtained by tillage with CH 3 COONa.

The acidity of the soil is determined not only by hydrogen ions, but also by aluminum:

Aluminum hydroxide precipitates, and the system is practically no different from the one that contains only absorbed hydrogen ions. But even if AlCl% remains in solution, then during titration

AlCl 3 + 3 NaOH \u003d A (OH) 3 + 3 NaCl

which is equivalent to the reaction

3 HCl + 3 NaOH = 3 NaCl + 3 H 2 O. The absorbed aluminum ions are also displaced when the soil is cultivated with a solution of CH 3 COONa. In this case, all of the displaced aluminum precipitates in the form of hydroxide.

According to the degree of acidity, determined in a salt extract of 0.1n. KKCl potentiometrically, soils are divided into:

Determination of pH, exchangeable acidity and mobilealuminum according to Sokolov

The determination of exchangeable acidity is based on the displacement of hydrogen and aluminum ions 1.0 n from the FPC. KKCl solution:

The resulting acid is titrated with alkali and the value of exchangeable acidity is calculated, due to the sum of hydrogen and aluminum ions. Al is precipitated with 3.5% NaF solution.

Repeated titration of the solution allows you to determine the acidity due to only hydrogen ions.

According to the difference between the data of the first and second titration, the aluminum content in the soil is calculated.

Analysis progress

1. On technical scales, take a sample of 40 g of air-dry soil using the average sample method.

2. Transfer the sample to a 150-300 ml conical flask.

3. Pour 100 ml of 1.0 N from a burette. KCl (pH 5.6-6.0).

4. Shake on a rotator for 1 hour or shake for 15 minutes. and leave overnight.

5. Filter through a dry paper pleated funnel, discarding the first portion of the filtrate.

6. Determine the pH value in the filtrate potentiometrically.

7. To determine the exchangeable acidity, pipette 25 ml of the filtrate into a 100 ml Erlenmeyer flask.

8. Boil the filtrate on a burner or electric stove for 5 minutes. hourglass to remove carbon dioxide.

9. Add 2 drops of phenolphthalein to the filtrate and titrate the hot solution with 0.01 or 0.02 N. alkali solution (KOH or NaOH) to a stable pink color - 1st titration.

10. In another Erlenmeyer flask, pipette also 25 ml of the filtrate, boil for 5 minutes, cool in a water bath to room temperature.

11. Pour 1.5 ml of 3.5% sodium fluoride solution into the cooled filtrate with a pipette, mix.

12. Add 2 drops of phenolphthalein and titrate with 0.01 or 0.02 N. alkali solution to a slightly pink color - 2nd titration.

Calculation

1. Exchangeable acidity due to hydrogen and aluminum ions (according to the results of the 1st titration) in meq per 100 g of dry soil:

where: P - dilution 100/25=4; H - sample of soil in grams; K - coefficient of soil moisture; ml KOH - the amount of alkali used for titration; n. KOH - alkali normality.

2 Calculation of acidity due to hydrogen ions is the same, but according to the results of the second titration, after aluminum precipitation.

* When determining these indicators in moist soil, the percentage of moisture is simultaneously determined.

Reagents

1. Solution 1 n. KCl, 74.6 g chemically pure Dissolve KCl in 400-500 ml of distilled water, transfer to a 1 liter volumetric flask and make up to the mark. The pH of the reagent should be 5.6-6.0 (check before starting the analysis - if necessary, set the desired pH value by adding a 10% KOH solution)

2. 0.01 or 0.02 n. a solution of KOH or NaOH is prepared from a weighed portion of the reagent or fixanal.

3. 3.5% sodium fluoride solution, prepared with distilled water without CO 2 (boil distilled water, evaporating to 1/3 of the original volume).

Methods for determining priority pollutants in soils

Separately, in view of the relevance and importance of the problem, the need for analysis of heavy metals in soils should be mentioned. Identification of soil contamination with heavy metals is carried out by direct methods of soil sampling in the studied areas and their chemical analysis. A number of indirect methods are also used: visual assessment of the state of phytogenesis, analysis of the distribution and behavior of indicator species among plants, invertebrates and microorganisms. It is recommended to take soil and vegetation samples along the radius from the source of pollution, taking into account the prevailing winds along a route 25-30 km long. The distance from the source of pollution to detect the halo of pollution can vary from hundreds of meters to tens of kilometers. Determining the level of toxicity of heavy metals is not easy. For soils with different mechanical compositions and organic matter content, this level will be different. MPCs have been proposed for mercury - 25 mg/kg, arsenic - 12-15, cadmium - 20 mg/kg. Some detrimental concentrations of a number of heavy metals in plants (g / million) have been established: lead - 10, mercury - 0.04, chromium - 2, cadmium - 3, zinc and manganese - 300, copper - 150, cobalt - 5, molybdenum and nickel - 3, vanadium - 2. Cadmium. In acid soil solutions, it is present in the forms Cd 2+, CdCl +, CdSO 4, alkaline soils - Cd 2+, CdCl +, CdSO 4, CdHCO 3. Cadmium ions (Cd 2+) make up 80-90% of the total amount in solution, except for those soils that are contaminated with chlorides and sulfates. In this case, 50% of the total amount of cadmium is CdCl + and CdSO 4 . Cadmium is prone to active bioconcentration, which leads to a short time to its excess in bioavailable concentrations. Thus, cadmium is the most powerful soil toxicant compared to other heavy metals. Cadmium does not form its own minerals, but is present in the form of impurities, most of it in soils is represented by exchange forms (56-84%). Cadmium practically does not bind with humic substances. Lead. Soils are characterized by less soluble and less mobile forms of lead compared to cadmium. The content of this element in the water-soluble form is 1.4%, in the exchange - 10% of the gross; more than 8% of lead is associated with organic matter, most of this amount is fulvates. 79% of lead is associated with the mineral component of the soil. The concentration of lead in the soils of the background regions of the world is 1-80 mg/kg. The results of many years of worldwide research have shown an average lead content in soils of 16 mg/kg. Mercury. Mercury is the most toxic element in natural ecosystems. The Hg 2+ ion can be present in the form of individual organomercury compounds (methyl-, phenyl-, ethylmercury, etc.). Ions Hg 2+ and Hg + can be associated with minerals as part of their crystal lattice. At low pH values ​​of the soil suspension, most of the mercury is sorbed by organic matter, and as the pH increases, the amount of mercury associated with soil minerals increases.

Lead and cadmium

To determine the content of lead and cadmium in objects of the natural environment at the background level, the method of atomic absorption spectrophotometry (AAS) is most widely used. The AAS method is based on the atomization of the analyzed element transferred into solution in a graphite cell in an inert gas atmosphere and the absorption of the resonance line of the emission spectrum of the hollow cathode lamp of the corresponding metal. Lead absorption is measured at a wavelength of 283.3 nm, cadmium at a wavelength of 228.8 nm. The analyzed solution goes through the stages of drying, ashing and atomization in a graphite cell using high-temperature heating electric shock in an inert gas flow. The absorption of the resonance line of the emission spectrum of a hollow cathode lamp of the corresponding element is proportional to the content of this element in the sample. During electrothermal atomization in a graphite cuvette, the limit of detection for lead is 0.25 ng/ml, for cadmium 0.02 ng/ml.

Solid soil samples are put into solution as follows: 5 g of air-dry soil is placed in a quartz cup, poured with 50 ml of concentrated nitric acid, carefully evaporated to a volume of approximately 10 ml, 2 ml of 1 N hydrochloric acid are added. nitric acid solution. The sample is cooled and filtered. The filtrate is diluted to 50 ml with bidistilled water in a volumetric flask. A 20 μl aliquot of the sample is introduced into a graphite cuvette with a micropipette and the concentration of the element is measured.

Mercury

The most selective and highly sensitive method for determining the mercury content in various natural objects is the cold vapor atomic absorption method. Soil samples are mineralized and dissolved with a mixture of sulfuric and nitric acids. The resulting solutions are analyzed by atomic absorption. Mercury in the solution is reduced to metallic mercury and, using an aerator, mercury vapor is fed directly into the cuvette of an atomic absorption spectrophotometer. The limit of detection is 4 µg/kg.

The measurements are carried out as follows: the equipment is put into operation, the microprocessor is turned on, the dissolved sample with a volume of 100 ml is poured into the sample, then 5 ml of a 10% tin chloride solution is added and an aerator with a stopper on the thin section is immediately inserted. The maximum reading of the spectrophotometer is fixed, according to which the concentration is calculated.

2. Plant analysis

Plant analysis allows us to solve the following problems.

1. Investigate the transformation of macro- and microelements in the soil-plant-fertilizer system under various plant growing regimes.

2. Determine the content of the main biocomponents in plant objects and feed: proteins, fats, carbohydrates, vitamins, alkaloids and the correspondence of their content accepted norms and standards.

3. Assess the suitability of plants for the consumer (nitrates, heavy metals, alkaloids, toxicants).

Plant sampling

Plant sampling is a critical stage of work that requires certain skills and experience. Errors in sampling and preparation for analysis are not compensated by high-quality analytical processing of the collected material. The basis for sampling plants in agro- and biocenoses is the method of average sampling. In order for the average sample to reflect the status of the entire population of plants, macro- and microrelief, hydrothermal conditions, evenness and density of plant standing, and their biological characteristics are taken into account.

Plant samples are taken in dry weather, in the morning, after the dew has dried. When studying metabolic processes in plants in dynamics, these hours are observed throughout the entire growing season.

There are continuous sowing crops: wheat, oats, barley, cereals, grasses, etc. and tilled crops: potatoes, corn, beets, etc.

For continuous sowing crops, 5-6 plots 0.25-1.00 m 2 in size are uniformly allocated on the experimental plot, plants from the plot are mowed at a height of 3-5 cm. The total volume of the material taken is a combined sample. After careful averaging of this sample, an average sample of 1 kg is taken. An average sample is weighed, and then analyzed by botanical composition, accounting for weeds, diseased plants, which are excluded from the sample.

The division of plants into organs is carried out with weight accounting in the sample of leaves, stems, cobs, flowers, ears. Young plants are not differentiated by organs and are fixed as a whole. For row crops, especially tall crops such as corn, sunflower, etc. a combined sample is made up of 10-20 plants of medium size, taken diagonally from the plot or alternately in non-adjacent rows.

When selecting root crops, 10-20 plants of medium size are dug up, cleaned of soil, dried, weighed, above-ground organs are separated and root crops are weighed.

The average sample is made taking into account the size of tubers, cobs, baskets, etc. To do this, the material is visually sorted into large, medium, small, and, accordingly, the share of the fraction constitutes the average sample. In tall crops, the sample can be averaged by longitudinal dissection of the entire plant from top to bottom.

The criterion for assessing the correct sampling is the convergence of the results of chemical analysis in parallel determinations. The rate of chemical reactions in plant samples taken during the period of active vegetation is much higher than in many analyzed objects. Due to the work of enzymes, biochemical processes continue, resulting in the decomposition of substances such as starch, proteins, organic acids, and especially vitamins. The task of the researcher is to reduce to a minimum the period from sampling to analysis or fixation of plant material. Reducing the rate of reactions can be achieved by working with fresh plants in the cold in a climate chamber (+4°C), as well as short-term storage in a domestic refrigerator. In fresh plant material at natural humidity, water-soluble forms of proteins, carbohydrates, enzymes, potassium, phosphorus are determined, and the content of nitrates and nitrites is determined. With a small error, these determinations can be performed in plant samples after freeze drying.

In fixed air-dry samples, all macronutrients are determined, i.e. ash composition of plants, the total content of proteins, carbohydrates, fats, fiber, pectin substances. Drying of plant samples to absolute dry weight for analysis is unacceptable, since the solubility and physicochemical properties of many organic compounds are disturbed, and irreversible denaturation of proteins occurs. When analyzing the technological properties of any objects, drying is allowed at a temperature not exceeding 30°C. Elevated temperatures change the properties of protein-carbohydrate complexes in plants and distort the results of the determination.

Fixation of plant material

Preservation of organic and ash substances in plant samples in quantities close to their natural state is carried out due to fixation. Temperature fixation and freeze drying are used. In the first case, the stabilization of the composition of plants is carried out due to the inactivation of enzymes, and in the second case, due to sublimation, while plant enzymes remain in an active state, proteins do not denature. Temperature fixation of plant material is carried out in an oven. The plant material is placed in kraft paper bags and loaded into an oven preheated to 105-110°C. After loading, the temperature is maintained at 90-95°C for 10-20 minutes, depending on the properties of the plant material. With such a temperature treatment due to water vapor, plant enzymes are inactivated. At the end of fixation, the plant material should be moist and sluggish, while it should retain its color. Further drying of the sample is carried out with access to air in open bags at a temperature of 50-60°C for 3-4 hours. The indicated temperature and time intervals should not be exceeded. Prolonged heating at high temperature leads to the thermal decomposition of many nitrogen-containing substances and caramelization of plant mass carbohydrates. Plant samples with a high water content - roots, fruits, berries, etc. divided into segments so that the analysis includes the peripheral and central parts of the fetus. A set of segments for sampling is made up of segments of large, medium and small fruits or tubers in the appropriate ratio of them in the crop. Segments of the average sample are crushed and fixed in enameled cuvettes. If the samples are voluminous, then the aerial part of the plants is crushed immediately before fixation and quickly closed in bags. If the samples are supposed to determine only a set of chemical elements, they can not be fixed, but dried at room temperature. Drying of plant material is best done in a thermostat at a temperature of 40-60 0 C, since at room temperature the mass may rot and become contaminated with dust particles from the atmosphere. Samples of grain and seeds are not subjected to temperature fixation, but they are dried at a temperature not exceeding 30°C. Lyophilization of plant material (drying by sublimation) is based on the evaporation of ice bypassing the liquid phase. Drying of the material during lyophilization is carried out as follows: the selected plant material is frozen to a solid state, filling the sample with liquid nitrogen. The sample is then placed in a lyophilizer where it is dried at low temperature and under vacuum. In this case, moisture is absorbed by a special desiccant (reagent), which is used as silica gel, calcium chloride, etc. Freeze drying inhibits enzymatic processes, but the enzymes themselves are preserved.

Grinding of plant samples and their storage.

The grinding of plants is carried out in an air-dry state. The grinding speed increases if the samples are pre-dried in a thermostat. The absence of hygroscopic moisture in them is determined visually: fragile, easily broken stems and leaves in the hands are the most suitable material for grinding.

For grinding bulk samples weighing more than 30 g, laboratory mills are used; for grinding small samples, household coffee grinders are used. At very small quantities, plant samples are ground in a porcelain mortar, followed by passing the material through a sieve. The crushed material is sifted through a sieve. The diameter of the holes depends on the specifics of the analysis: from 1 mm to 0.25 mm. The part of the material that has not passed through the sieve is re-ground in a mill or in a mortar. "Rejection" of plant material is not allowed, as this changes the composition of the average sample. With a large volume of ground samples, it is possible to reduce the volume by moving from an average laboratory sample to an average analytical one, the weight of the latter is 10-50 g, and for grain at least 100 g. The selection is made by quartering. The laboratory sample is evenly distributed on paper or glass in the form of a circle or square. Spatula is divided into small squares (1-3 cm) or segments. Material from non-adjacent squares is taken into the analytical sample.

Determination of various substances in plant material

Determination of water-soluble forms of carbohydrates

The content of carbohydrates and their diversity are determined by the plant species, development phase and abiotic environmental factors and vary widely. There are quantitative methods for the determination of monosaccharides: chemical, polarimetric. Determination of polysaccharides in plants is carried out by the same methods, but, first, the oxygen bond (-O-) of these compounds is destroyed in the process of acid hydrolysis. One of the main methods of determination - the Bertrand method is based on the extraction of soluble carbohydrates from plant material with hot distilled water. In one part of the filtrate, monosaccharides are determined, in the other - after hydrolysis hydrochloric acid- di- and trisaccharides, which decompose at the same time to glucose

Determination of potassium, phosphorus, nitrogen based on the reactions of hydrolysis and oxidation of plant organic substances with strong oxidizing agents (a mixture of sulfuric and chlorine to-t). The main oxidizing agent is perchloric acid (HclO 4). Nitrogen-free organic substances are oxidized to water and carbon dioxide, releasing ash elements in the form of oxides. Nitrogen-containing organic compounds are hydrolyzed and oxidized to water and carbon dioxide, releasing nitrogen in the form of ammonia, which is immediately bound by sulfuric acid. Thus, in solution there are ash elements in the form of oxides and nitrogen in the form of ammonium sulphate and ammonium salt of perchloric acid. The method eliminates the loss of nitrogen, phosphorus and potassium in the form of their oxides, since the plant matter is exposed at a temperature of 332°C. This is the boiling point of sulfuric acid, while perchloric acid has a much lower boiling point - 121 ° C.

Definitionnitrate and nitrite content. Plants accumulate nitrates and nitrites in large quantities. These compounds are toxic to humans and animals, nitrites are especially dangerous, the toxicity of which is 10 times higher than that of nitrates. Nitrites in the human and animal body convert the ferrous iron of hemoglobin to trivalent. The resulting metahemoglobin is unable to carry oxygen. Strict control over the content of nitrates and nitrites in crop products is necessary. A number of methods have been developed to determine the content of nitrates in plants. The most widely used ionometric express method. Nitrates are extracted with a solution of potassium alum, followed by measurement of the concentration of nitrates in the solution using an ion-selective electrode. The sensitivity of the method is 6 mg/dm 3 . The limit of determination of nitrates in a dry sample is 300 ml -1 , in a raw one - 24 -30 ml - 1 . Let us dwell in more detail on the analysis of total nitrogen in plants.

Determination of total nitrogen by Kbeldalu

A higher nitrogen content is observed in generative organs, especially in grain, and its concentration is lower in leaves, stems, roots, root crops, and very little in straw. Total nitrogen in a plant is represented by two forms: protein nitrogen and nitrogen of non-protein compounds. The latter include nitrogen, which is part of amides, free amino acids, nitrates and ammonia.

The protein content in plants is determined by the amount of protein nitrogen. The content of protein nitrogen (in percent) is multiplied by a factor of 6.25 when analyzing vegetative organs and root crops and by 5.7 when analyzing grain. The non-protein forms of nitrogen account for 10-30% of the total nitrogen in the vegetative organs, and no more than 10% in the grain. The content of non-protein nitrogen decreases by the end of the growing season, therefore, under production conditions, its share is neglected. In this case, the total nitrogen is determined (as a percentage) and its content is converted to protein. This indicator is called "crude protein", or protein. Method principle. A portion of plant material is incinerated in a Kjeldahl flask with concentrated sulfuric acid in the presence of one of the catalysts (metal selenium, hydrogen peroxide, perchloric acid, etc.) Ashing temperature 332°C. In the process of hydrolysis and oxidation of the organic mass, nitrogen in the flask is stored in solution in the form of ammonium sulfate.

Ammonia is distilled off in a Kjeldahl apparatus by heating and boiling the solution.

In an acidic environment, there is no hydrolytic dissociation of ammonium sulfate, the partial pressure of ammonia is zero. In an alkaline environment, the equilibrium shifts, and ammonia is formed in the solution, which easily evaporates when heated.

2NH 4 OH \u003d 2NH 3 * 2H 2 0.

Ammonia is not lost, but passes through the refrigerator first in the form of a gas, and then, condensing, drops into the receiver with titrated sulfuric acid and binds with it, again forming ammonium sulfate:

2NH 3 + H 2 SO 4 \u003d (NH 4) 2 S0 4.

An excess of acid, not associated with ammonia, is titrated with an alkali of precisely established normality using a combined indicator or methyl rota.

Analysis progress

1. On an analytical balance, take a sample of plant material? 0.3-0.5 ± 0.0001 g using a test tube (according to the difference between the weight of the test tube with the sample and the weight of the test tube with the remains of the material) and, putting on the end of the test tube a rubber tube 12- 15 cm, carefully lower the sample to the bottom of the Kjeldahl flask. Pour into the flask with a small cylinder 10-12 ml of concentrated sulfuric acid (d=1.84). Uniform ashing of plant material begins already at room temperature, so it is better to leave acid-filled samples overnight.

2. Put the flasks on the electric stove and carry out gradual combustion, first on low heat (put asbestos), then on high, periodically shaking gently. When the solution becomes homogeneous, add a catalyst (a few crystals of selenium or a few drops of hydrogen peroxide) and continue burning until the solution is completely discolored.

Catalysts. The use of catalysts contributes to the increase in the boiling point of sulfuric acid and the acceleration of ashing. In various modifications of the Kjeldahl method, metal mercury and selenium, potassium sulfate, copper sulfate, hydrogen peroxide are used. It is not recommended to use perchloric acid alone or mixed with sulfuric acid for combustion as a catalyst. The rate of oxidation of the material is ensured in this case not due to an increase in temperature, but due to the rapid release of oxygen, which is accompanied by nitrogen losses during ashing.

3. Ammonia stripping. After the end of combustion, the Kjeldahl flask is cooled and distilled water is carefully poured into it along the walls, the contents are mixed and the neck of the flask is rinsed. The first portion of water is poured up to the neck and quantitatively transferred to a 1 L round bottom flask. The Kjeldahl flask is washed 5-6 more times with small portions of hot distilled water, draining each time the washing water into the distilling flask. Fill the distilling flask with washing water up to 2/3 of the volume and add 2-3 drops of phenolphthalein. A small amount of water makes it difficult to vaporize during distillation, and a large amount can cause boiling water to transfer to the refrigerator.

4. Pour 25-30 ml of 0.1 n. H 2 SO 4 (with a precisely set titer), add 2-3 drops of methylroth indicator or Groak's reagent (purple color). The tip of the refrigerator tube is immersed in acid. The stripping flask is placed on the heater and connected to the refrigerator, checking the tightness of the connection. To destroy ammonium sulfate and remove ammonia, a 40% alkali solution is used, taken in a volume that is four times the volume of concentrated sulfuric acid taken during sample combustion.

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When determining the needs of plants for fertilizers, along with agrochemical analyzes of the soil, field and vegetation experiments, microbiological and other methods, methods of plant diagnostics have been increasingly used.
Currently, the following methods of plant diagnostics are widely used: 1) chemical analysis of plants, 2) visual diagnostics and 3) injection and spraying. Chemical analysis of plants is the most common method for diagnosing the need for fertilizer application.
Chemical diagnostics is represented by three types: 1) leaf diagnostics, 2) tissue diagnostics, and 3) fast (express) methods of plant analysis.
Important steps in plant diagnostics using chemical analysis are: 1) taking a plant sample for analysis; 2) taking into account the accompanying conditions of plant growth; 3) chemical analysis of plants; 4) processing of analytical data and drawing up a conclusion on the need for plants in fertilizers.
Taking plant samples for analysis. When selecting plants for analysis, care should be taken to ensure that the plants taken correspond to the average condition of plants in a given section of the field. If the sowing is homogeneous, then one sample can be limited; if there are spots of better developed or, conversely, worse developed plants, then a separate sample is taken from each of these spots to determine the cause of the altered state of the plant. The nutrient content of well-developed plants can be used in this case as an indicator of the normal composition of a given plant species.
When conducting analyzes, it is necessary to unify the technique of taking and preparing a sample: taking the same parts of a plant by layering, position on the plant, and physiological age.
The choice of plant part for analysis depends on the method chemical diagnostics. To obtain reliable data, it is necessary to take samples from at least ten plants.
In tree crops, due to the peculiarities of their age-related changes, taking plant samples is somewhat more difficult than in field crops. It is recommended to conduct research in the following age periods: seedlings, seedlings, young and fruiting plants. Leaves, their petioles, buds, shoots or other organs should be taken from the upper third of the shoots from the middle zone of the crown of trees or shrubs of the same age and quality, adhering to the same order, namely: either only from fruit shoots, or only from non-fruit shoots, or from shoots of current growth, or leaves in direct sunlight or diffused light. All these points must be taken into account, since they all affect the chemical composition of the leaves. It is noted that the best correlation between the chemical composition of the leaf and the yield of fruits is obtained if a leaf is taken as a sample, in the axil of which a flower bud develops.
At what phase of plant development should samples be taken for analysis? If we keep in mind obtaining the best correlation with the harvest, then the analysis of plants in the flowering or maturation phase turns out to be the best. Thus, Lundegard, Kolarzhik and other researchers believe that flowering is such a phase for all plants, since by this moment the main growth processes are over and the mass gain will not “dilute” the percentage of substances.
To solve the problem of how to change the nutrition of plants in order to ensure the formation best harvest, it is necessary to analyze plants in earlier periods of development and not once, but several times (three or four), starting with the appearance of one or two leaves.
Sampling time. I term: for spring cereals (wheat, oats, corn) - in the three-leaf phase, i.e., before the start of differentiation of the embryonic ear or panicle; for flax - the beginning of the "Christmas tree"; for potatoes, legumes, cotton and others - the phase of four to five true leaves, i.e. before budding; for sugar beet - the phase of three true leaves.
II term: for spring cereals - in the phase of five leaves, i.e., in the phase of piping; for beets - in the phase of deployment of the sixth leaf; for everyone else - during the formation of the first small green buds, i.e., to the very beginning of budding.
III term: in the flowering phase; for beets - when deploying the eighth-ninth leaf.
IV term: in the phase of milk ripeness of seeds; for beets - a week before harvesting.
In woody plants and berries, samples are taken according to the following phases of crop formation: a) before flowering, i.e. at the beginning of strong growth, b) flowering, i.e. during the period of strong growth and physiological shedding of ovaries, c) fruit formation, d ) ripening and harvesting; and e) the period of autumn leaf fall.
When establishing the timing of plant sampling, it is also necessary to take into account during which period of growth and development critical nutritional levels occur. The term "critical levels" means the lowest concentrations of nutrients in plants during the critical period of their development, i.e., concentrations below which the plant deteriorates and yield decreases. The optimal composition of a plant is understood as such a content of nutrients in it in the critical phases of its development, which ensures a high yield.
The values ​​of critical levels and the optimal composition are given for some cultures below. Samples are taken in all cases at the same hours of the day, preferably in the morning (at 8-9 o'clock), in order to avoid changes in the composition of plants due to the daily diet.
Accounting for related conditions. It is not always correct to judge the sufficiency or insufficiency of plant nutrition with certain elements only according to chemical analysis. Many facts are known when a lack of one or more nutrients, a delay in photosynthesis or a violation of water, thermal and other vital regimes can cause the accumulation of one or another element in a plant, which in no case should characterize the sufficiency of this element in the nutrient medium (soil ). To avoid possible errors and inaccuracies in the conclusions, it is necessary to compare the data of the chemical analysis of plants with a number of other indicators: with the weight, growth and rate of development of plants at the time of sampling and with the final harvest, with visual diagnostic signs, with the features of agricultural technology, with the agrochemical properties of the soil, with weather conditions and a number of other indicators affecting plant nutrition. Therefore, one of the most important conditions for the successful use of plant diagnostics is the most detailed account of all these indicators for their subsequent comparison with each other and with the analysis data.

Doubt the authenticity of the purchased medicinal product? Habitual medicines suddenly stopped helping, having lost their effectiveness? So, it is worth conducting their full analysis - pharmaceutical expertise. It will help to establish the truth and reveal a fake in the shortest possible time.

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What is Pharmaceutical Expertise

A pharmacological study is a set of analyzes designed to establish the composition, compatibility of ingredients, type, effectiveness and direction of the drug. All this is necessary when registering new medicines and re-registering old ones.

Typically, the study consists of several stages:

  • Studies of raw materials in production and chemical analysis of medicinal plants.
  • Microsublimation method or isolation and analysis of active substances from plant materials.
  • Analysis and comparison of quality with current standards set by the Ministry of Health.

The study of drugs is a complex and painstaking process, which is subject to hundreds of requirements and norms that must be followed. Not every organization has the right to hold it.

Licensed specialists who can boast of all the admission rights can be found in the ANO "Center for Chemical Expertise". In addition, the non-profit partnership - the Center for Expertise of Medicines - is famous for its innovative laboratory, in which modern equipment functions properly. This allows you to carry out the most complex analyzes in the shortest possible time and with phenomenal accuracy.

Registration of results by specialists from the NP is carried out strictly in accordance with the requirements of the current legislation. The conclusions are filled in special forms of the state sample. This gives the results of the study legal force. Each conclusion from the ANO "Center of Chemical Expertise" can be attached to the case and used during the trial.

Features of drug analysis

Laboratory studies are the basis for the examination of medicines. It is they that allow you to identify all components, evaluate their quality and safety. There are three types of pharmaceutical research:

  • Physical. Many indicators are subject to study: melting and solidification temperatures, density indicators, refraction. Optical rotation, etc. Based on them, the purity of the product and its compliance with the composition are determined.
  • Chemical. These studies require strict adherence to proportions and procedures. These include: the determination of toxicity, sterility, as well as the microbiological purity of medicines. Modern chemical analysis of drugs requires strict adherence to safety precautions and the presence of protection for the skin and mucous membranes.
  • Physical and chemical. These are quite complex techniques, including: spectrometry of various types, chromatography and electrometry.

All these studies require modern equipment. It can be found in the laboratory complex of ANO "Center for Chemical Expertise". Modern installations, an innovative centrifuge, a lot of reagents, indicators and catalysts - all this helps to increase the speed of reactions and maintain their reliability.

What should be in the laboratory

Not every expert center can provide everything for a pharmacological study. necessary equipment. While ANO "Center for Chemical Expertise" already has:

  • Spectrophotometers of various action spectrum (infrared, UV, atomic absorption, etc.). They measure authenticity, solubility, homogeneity and the presence of metal and non-metal impurities.
  • Chromatographs of various directions (gas-liquid, liquid and thin-layer). They are used to determine authenticity, qualitatively measure the amount of each ingredient, the presence of related impurities and uniformity.
  • Polarimeter is a device necessary for fast chemical analysis of medicines. It will help determine the authenticity and quantitative indicators of each ingredient.
  • Potentiometer. The device is useful for determining the rigidity of the composition, as well as quantitative indicators.
  • Fischer Titrator. This device shows the amount of H2O in the preparation.
  • A centrifuge is a specific technique that allows you to increase the speed of reactions.
  • Derivatograph. This device allows you to determine the residual mass of the agent after the drying process.

This equipment, or at least its partial availability, is an indicator of the high quality of the laboratory complex. It is thanks to him that in ANO "Center for Chemical Expertise" all chemical and physical reactions take place at maximum speed and without loss of accuracy.

ANO "Center of Chemical Expertise": reliability and quality

Urgently need a chemical analysis of medicinal plants? Would you like to establish the authenticity of the purchased medicines? So, it is worth contacting the ANO "Center for Chemical Expertise". This is an organization that brings together hundreds of professionals - the staff of the non-profit partnership has more than 490 specialists.

With them you get a lot of advantages:

  • High research accuracy. This result was achieved by specialists thanks to a modern laboratory and innovative equipment.
  • The speed of results is impressive. Qualified specialists are ready to arrive anywhere in the state at your first request. This speeds up the process. While others are waiting for the state executor, you are already getting the result.
  • Legal force. All conclusions are filled in accordance with current legislation on official papers. You can use them as strong evidence in court.

Still looking for a drug expertise center? Think you've found it! By contacting ANO "Center of Chemical Expertise" you are guaranteed to receive accuracy, quality and reliability!

History of the study of plant physiology. The main sections of plant physiology

Plant physiology as a branch of botany.

The topic of the work must be agreed with the curator of the discipline of choice (elective) A.N. Luferov.

Features of the structure of a plant cell, chemical composition.

1. History of the study of plant physiology. The main sections and tasks of plant physiology

2. Basic methods for studying plant physiology

3. Structure of a plant cell

4. Chemical composition of the plant cell

5. Biological membranes

Plant physiology is a science that studies the life processes that occur in a plant organism.

Information about the processes occurring in a living plant accumulated with the development of botany. The development of plant physiology, as a science, was determined by the use of new, more advanced methods of chemistry, physics, and the needs of agriculture.

Plant physiology originated in the 17th-18th centuries. The beginning of plant physiology as a science was laid by the experiments of J.B. Van Helmont on the water nutrition of plants (1634).

The results of a number of physiological experiments proving the existence of descending and ascending currents of water and nutrients, air nutrition of plants are set out in the classic works of the Italian biologist and physician M. Malpighi "Plant Anatomy" (1675-1679) and the English botanist and physician S. Gales "Statics plants "(1727). In 1771, the English scientist D. Priestley discovered and described the process of photosynthesis - air nutrition of plants. In 1800, J. Senebier published a treatise “Physiologie vegetale” in five volumes, in which all the data known by that time were collected, processed and comprehended, the term “physiology of plants” was proposed, tasks were defined, methods for studying plant physiology, experimentally proved that carbon dioxide is the source of carbon in photosynthesis, laid the foundations of photochemistry.

In the 19th - 20th centuries, a number of discoveries were made in the field of plant physiology:

1806 - T.A. Knight described and experimentally studied the phenomenon of geotropism;

1817 - P.J. Peltier and J. Kavantou isolated a green pigment from leaves and called it chlorophyll;

1826 - G. Dutrochet discovered the phenomenon of osmosis;

1838-1839 - T. Schwann and M. Ya. Schleiden substantiated the cellular theory of the structure of plants and animals;

1840 - J. Liebig developed the theory of mineral nutrition of plants;

1851 - V.Hofmeister discovered the alternation of generations in higher plants;

1859 - C. Darwin laid the foundations of evolutionary plant physiology, flower physiology, heterotrophic nutrition, movement and irritability of plants;


1862 - J. Sachs showed that starch is a product of photosynthesis;

1865 - 1875 - K.A. Timiryazev studied the role of red light in the processes of photosynthesis, developed an idea of ​​the cosmic role of green plants;

1877 - W. Pfeffer discovered the laws of osmosis;

1878-1880 - G. Gelrigel and J. B. Boussengo showed the fixation of atmospheric nitrogen in legumes in symbiosis with nodule bacteria;

1897 M. Nentsky and L. Markhlevsky discovered the structure of chlorophyll;

1903 - G. Klebs developed the doctrine of the influence of environmental factors on the growth and development of plants;

1912 - V.I. Palladin put forward the idea of ​​anaerobic and aerobic stages of respiration;

1920 - W. W. Garner and G. A. Allard discovered the phenomenon of photoperiodism;

1937 - G.A. Krebs described the citric acid cycle;

1937 - M.Kh Chailakhyan put forward the hormonal theory of plant development;

1937 -1939 – G.Kalkar and V.A.Blitser discovered oxidative phosphorylation;

1946 - 1956 - M. Calvin and co-workers deciphered the main pathway of carbon in photosynthesis;

1943-1957 – R. Emerson experimentally proved the existence of two photosystems;

1954 - D.I. Arnon et al. discovered photophosphorylation;

1961-1966 – P. Mitchel developed the chemiosmotic theory of coupling of oxidation and phosphorylation.

As well as other discoveries that determined the development of plant physiology as a science.

The main sections of plant physiology were differentiated in the 19th century - these are:

1. physiology of photosynthesis

2. physiology of the water regime of plants

3. physiology of mineral nutrition

4. physiology of growth and development

5. physiology of resistance

6. physiology of reproduction

7. physiology of respiration.

But any phenomena in a plant cannot be understood within the framework of only one section. Therefore, in the second half of the XX century. in plant physiology, there is a tendency to merge into a single whole biochemistry and molecular biology, biophysics and biological modeling, cytology, anatomy and genetics of plants.

Modern plant physiology is a fundamental science, its main task is to study the patterns of plant life. But it is of great practical importance, so its second task is to develop theoretical foundations obtaining maximum yields of agricultural, industrial and medicinal crops. Plant physiology is the science of the future, its third, as yet unsolved, task is the development of installations for the implementation of photosynthesis processes in artificial conditions.

Modern plant physiology uses the entire arsenal of scientific methods that exists today. These are microscopic, biochemical, immunological, chromatographic, radioisotope, etc.

Let us consider the instrumental research methods widely used in the study of physiological processes in a plant. Instrumental methods of working with biological objects are divided into groups depending on any criterion:

1. Depending on where the sensitive elements of the device are located (on the plant or not): contact and remote;

2. By the nature of the value obtained: qualitative, semi-quantitative and quantitative. Qualitative - the researcher receives information only about the presence or absence of a substance or process. Semi-quantitative - the researcher can compare the capabilities of one object with others in terms of the intensity of a process, in terms of the content of substances (if it is not expressed in numerical form, but, for example, in the form of a scale). Quantitative - the researcher receives numerical indicators characterizing any process or content of substances.

3. Direct and indirect. When using direct methods, the researcher receives information about the process under study. Indirect methods are based on measurements of any accompanying quantities, one way or another related to the studied one.

4. Depending on the conditions of the experiment, the methods are divided into laboratory and field.

When conducting research on plant objects, the following types of measurements can be carried out:

1. Morphometry (measurement of various morphological indicators and their dynamics (for example, leaf surface area, ratio of areas of aboveground and underground organs, etc.)

2. Weight measurements. For example, determining the daily dynamics of the accumulation of vegetative mass

3. Measurement of solution concentration, chemical composition of samples, etc. using conductometric, potentiometric and other methods.

4. Study of gas exchange (when studying the intensity of photosynthesis and gas exchange)

Morphometric indicators can be determined by visual counting, measuring with a ruler, graph paper, etc. To determine some indicators, for example, the total volume of the root system, special installations are used - a vessel with a graduated capillary. The volume of the root system is determined by the volume of water displaced.

When studying any process, various methods are used. For example, to determine the level of transpiration, use:

1. Weight methods (initial sheet weight and its weight after some time);

2. Temperature (use special climate chambers);

3. With the help of porometers, the humidity of the chamber where the test plant is placed is determined.

properties of all plant organisms and the internal structures inherent in individual species are determined by the multifaceted, constantly changing environmental influences. The influence of such factors as climate, soil, as well as the circulation of substances and energy is significant. Traditionally, to identify the properties of medicinal products or foodstuffs, the proportions of substances that can be isolated analytically are determined. But these individual substances cannot cover all the internal properties, for example, of medicinal and aromatic plants. Therefore, such descriptions of the individual properties of plants cannot satisfy all our needs. For an exhaustive description of the properties of herbal medicinal preparations, including biological activity, a comprehensive, comprehensive study is required. There are a number of methods to identify the quality and quantity of biologically active substances in the composition of the plant, as well as the places of their accumulation.

Luminescent microscopic analysis based on the fact that the biologically active substances contained in the plant give a bright colored glow in a fluorescent microscope, and different chemicals are characterized by different colors. So, alkaloids give a yellow color, and glycosides - orange. This method is mainly used to identify areas of accumulation of active substances in plant tissues, and the intensity of the glow indicates a greater or lesser concentration of these substances. Phytochemical analysis is designed to identify a qualitative and quantitative indicator of the content of active substances in the eastenium. Chemical reactions are used to determine the quality. The amount of active substances in a plant is the main indicator of its good quality, therefore, their volumetric analysis is also carried out using chemical methods. For the study of plants containing active substances such as alkaloids, coumarins,

glavones, which require not a simple summary analysis, but also their separation into components, are called chromatographic analysis. Chromatographic method of analysis was first introduced in 1903 by a botanist

color, and since then its various variants have been developed, which have an independent

meaning. This method of separating a mixture of g-zeetv into components is based on the difference in their physical and chemical properties. Using the photographic method, with the help of panoramic chromatography, you can make visible the internal structure of the plant, see the lines, shapes and colors of the plant. Such pictures, obtained from aqueous extracts, are retained on silver-nitrate filter paper and reproduced. The method for interpreting chromatograms is being successfully developed. This methodology is supported by data obtained using other, already known, proven methods.

Based on circulation chromodiagrams, the development of a panoramic chromatography method for determining the quality of a plant by the presence of nutrients concentrated in it continues. The results obtained using this method should be supported by data from the analysis of the acidity level of the plant, the interaction of the enzymes contained in its composition, etc. The main task further development The chromatographic method of plant analysis should be the search for ways to influence plant raw materials during their cultivation, primary processing, storage and at the stage of direct preparation of dosage forms in order to increase the content of valuable active substances in it.

Updated: 2019-07-09 22:27:53

  • It has been established that the adaptation of the body to various environmental influences is ensured by the corresponding fluctuations in the functional activity of organs and tissues, the central nervous