Chemical research methods in plants. Chemical analysis of medicinal plants. Obtaining a water solution of soils

26.11.2019

properties of all plant organisms and internal structures inherent in individual species are determined by the multifaceted, constantly changing influence environment. 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 internal properties, for example, 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-zeets 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 production 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

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 - Charles 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 cycle citric acid;

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. Mitchell 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 the theoretical foundations for 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 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.

Since botany studies quite a lot of different aspects of the organization and functioning of plant organisms, in each specific case, its own set of research methods is used. Botany uses both general methods (observation, comparison, analysis, experiment, generalization) and many

special methods (biochemical and cytochemical methods, light methods (conventional, phase-contrast, interference, polarization, fluorescence, ultraviolet) and electron (transmission, scanning) microscopy, cell culture methods, microscopic surgery, molecular biology methods, genetic methods, electrophysiological methods, freezing and chipping methods, biochronological methods, biometric methods, mathematical modeling, statistical methods).
Special methods take into account the peculiarities of one or another level of organization of the plant world. So, to study the lower levels of organization, various biochemical methods, methods of qualitative and quantitative chemical analysis are used. Various cytological methods are used to study cells, especially electron microscopy methods. To study tissues and the internal structure of organs, methods of light microscopy, microscopic surgery, and selective staining are used. To study the flora at the population-species and biocenotic levels, various genetic, geobotanical and ecological research methods are used. In the taxonomy of plants, an important place is occupied by such methods as comparative morphological, paleontological, historical, and cytogenetic.

The assimilation of material from different sections of botany is the theoretical basis for the training of future specialists in agricultural chemists and soil scientists. Due to the inextricable relationship between the plant organism and the environment of its existence, the morphological features and internal structure of the plant are largely determined by the characteristics of the soil. At the same time, the direction and intensity of the course of physiological and biochemical processes also depend on the chemical composition of the soil and its other properties, which ultimately determines the increase in plant biomass and the productivity of crop production as an industry as a whole. So botanical knowledge make it possible to substantiate the need and doses of applying various substances to the soil, to influence the yield of cultivated plants. In fact, any impact on the soil in order to increase the yield of cultivated and wild plants is based on data obtained in various sections of botany. The methods of biological control of plant growth and development are based almost entirely on botanical morphology and embryology.

In turn, the plant world is an important factor in soil formation and determines many properties of the soil. Each type of vegetation is characterized by certain types of soils, and these patterns are successfully used for mapping soils. Plant species and their individual systematic groups can be reliable phytoindicators of food (ground) conditions. Indicator geobotany gives soil scientists and agrochemists one of the important methods for assessing the quality of soils, their physicochemical and chemical properties,
Botany is the theoretical basis of agricultural chemistry, as well as applied areas such as crop production and forestry. About 2,000 plant species have now been introduced into cultivation, but only an insignificant part of them is widely grown. Many wild-growing species of flora can become very promising crops in the future. Botany substantiates the possibility and expediency of agricultural development of natural areas, carrying out land reclamation measures to increase the productivity of natural plant groups, in particular meadows and forests, promotes the development and rational use of plant resources on land, fresh water bodies and the World Ocean.
For specialists in the field of agrochemistry and soil science, botany is the basic basis, which allows a deeper understanding of the essence of soil-forming processes, to see the dependence of certain soil properties on the characteristics of the vegetation cover, and to understand the needs of cultivated plants for specific nutrients.

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.

But where to order such an important study? In state laboratories, the full range of analyzes can take weeks or even months, and they are not in a hurry to collect source files. How to be? It is worth contacting the ANO "Center for Chemical Expertise". This is an organization that has brought together professionals who can confirm their qualifications by having a license.

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:

Study of raw materials in production and chemical analysis 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.

Study medicines is a complex and painstaking process, to which hundreds of requirements and norms are mandatory. 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 various types, chromatography and electrometry.

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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

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FEDERAL AGENCY FOR EDUCATION

VORONEZH STATE UNIVERSITY

INFORMATION AND ANALYTICAL SUPPORT OF ENVIRONMENTAL ACTIVITIES IN AGRICULTURE

Educational and methodical manual for universities

Compiled by: L.I. Brekhova L.D. Stakhurlova D.I. Shcheglov A.I. Gromovik

VORONEZH - 2009

Approved by the Scientific and Methodological Council of the Faculty of Biology and Soil - Protocol No. 10 dated June 4, 2009

Reviewer Doctor of Biological Sciences, Professor L.A. Yablonsky

The teaching aid was prepared at the Department of Soil Science and Land Management of the Faculty of Biology and Soil of Voronezh State University.

For the specialty: 020701 - Soil science

The lack or excess of any chemical element causes a disruption in the normal course of biochemical and physiological processes in plants, which ultimately changes the yield and quality of crop products. Therefore, the determination of the chemical composition of plants and product quality indicators makes it possible to identify unfavorable environmental conditions for the growth of both cultivated and natural vegetation. In this regard, the chemical analysis of plant material is an integral part of environmental protection activities.

A practical manual on information and analytical support of environmental protection activities in agriculture was compiled in accordance with the program of laboratory classes in "Biogeocenology", "Plant Analysis" and "Environmental Protection in Agriculture" for students of the 4th and 5th years of the soil department of the Faculty of Biology and Soil VSU.

METHOD FOR COLLECTING PLANT SAMPLES AND PREPARING THEM FOR ANALYSIS

Taking plant samples is a very crucial moment in the effectiveness of diagnosing plant nutrition and assessing the availability of soil resources to them.

The entire area of the studied crop is visually divided into several sections depending on its size and the condition of the plants. If areas with obviously worse plants are identified in the sowing, then these areas are marked on the field map, it is found out whether the poor condition of the plants is the result of an entoly or phytodisease, local deterioration of soil properties or other growth conditions. If all these factors do not explain the reasons for the poor condition of the plants, then it can be assumed that their nutrition is disturbed. This is verified by plant diagnostic methods. Take pro-

from sites with the worst and best plants and the soil under them, and by their analyzes, they find out the reasons for the deterioration of plants and their level of nutrition.

If the sowing is not uniform in terms of the condition of the plants, then when sampling, it should be ensured that the samples correspond to the average condition of the plants in a given section of the field. Plants with roots are taken from each selected array along two diagonals. They are used: a) to take into account the weight gain and the course of organ formation - the future structure of the crop, and b) for chemical diagnostics.

In the early phases (with two or three leaves), the sample should contain at least 100 plants per 1 ha. Later for cereals, flax, buckwheat, peas and others - at least 25 - 30 plants per 1 ha. In large plants (adult corn, cabbage, etc.), the lower healthy leaves are taken from at least 50 plants. To take into account the accumulation by phases and the removal by the crop, the entire aerial part of the plant is taken into analysis.

At tree species - fruit, berry, grape, ornamental and forest - due to the peculiarities of their age-related changes, the frequency of fruiting, etc. sampling is somewhat more complicated than that of field crops. The following age groups are distinguished: seedlings, wildlings, grafted two-year-olds, seedlings, young and fruiting (beginning to bear fruit, in full and fading fruiting) trees. In seedlings, in the first month of their growth, the entire plant is included in the sample, followed by its division into organs: leaves, stems and roots. In the second and following months, fully formed leaves are selected, usually the first two after the youngest, counting from the top. The first two formed leaves are also taken from two-year-old wild birds, counting from the top of the growth shoot. In grafted two-year-olds and seedlings, as well as in adults, they take the middle leaves of growth shoots.

At berries - gooseberries, currants and others - are selected from the shoots of the current growth of 3 - 4 leaves from 20 bushes so that in the sample

there were at least 60 - 80 leaves. Adult leaves are taken from strawberries in the same amount.

The general requirement is the unification of sampling, processing and storage techniques: taking strictly the same parts from all plants according to their layering, age, location on the plant, absence of disease, etc. It also matters whether the leaves were in direct sunlight or in the shade, and in all cases, leaves of the same placement in relation to sunlight should be selected, preferably in the light.

When analyzing the root system, the average laboratory sample is carefully washed in water before weighing. tap water rinsed in distilled water and dried with filter paper.

A laboratory sample of grain or seeds is taken from many places (bag, box, machine) with a probe, then it is distributed in an even layer on paper in the form of a rectangle, divided into four parts and material is taken from two opposite parts to the desired amount for analysis.

One of important points in the preparation of plant material for analysis is the correct fixation of it, if the analyzes are not supposed to be carried out in fresh material.

For the chemical assessment of plant material according to the total content of nutrients (N, P, K, Ca, Mg, Fe, etc.), plant samples are dried to an air-dry state in an oven at

temperature 50 - 60 ° or in air.

In the analyzes, the results of which will draw conclusions about the state of living plants, fresh material should be used, since wilting causes a significant change in the composition of the substance or a decrease in its amount, and even the disappearance of substances contained in

living plants. For example, cellulose is not affected by degradation, while starch, proteins, organic acids and especially vitamins are decomposed after several hours of wilting. This forces the experimenter to carry out analyzes on fresh material in a very short time, which is not always possible. Therefore, fixation of plant material is often used, the purpose of which is to stabilize unstable plant substances. Enzyme inactivation is of decisive importance. Various methods of plant fixation are used depending on the objectives of the experiment.

Ferry fixing. This type of fixation of plant material is used when there is no need to determine water-soluble compounds (cell sap, carbohydrates, potassium, etc.). During processing of the raw plant material, autolysis can occur so strongly that the composition of the final product sometimes differs significantly from that of the starting material.

In practice, steam fixation is carried out as follows: inside the water bath is suspended metal grid, from above the bath is covered with dense non-combustible material and the water is heated to a rapid release of steam. After that, fresh plant material is placed on the mesh inside the bath. Fixation time 15 - 20 min. Then dry the plants

vatsya in a thermostat at a temperature of 60 °.

Temperature fixing. Plant material is placed in kraft paper bags, and crushed juicy fruits and vegetables are loosely placed in enameled or aluminum cuvettes. The material is kept for 10 - 20 minutes at a temperature of 90 - 95 °. This inactivates most of the enzymes. After that, the leaf-stem mass that has lost turgor and the fruits are dried in an oven at a temperature of 60 ° with or without ventilation.

When using this method of plant fixation, it must be remembered that prolonged drying of plant material at dark

temperatures of 80° and above lead to losses and changes in substances due to chemical transformations (thermal decomposition of certain substances, caramelization of carbohydrates, etc.), as well as due to the volatility of ammonium salts and some organic compounds. In addition, the temperature of the raw plant material cannot reach the ambient (drying cabinet) temperature until the water has evaporated and all the heat input has ceased to be converted into latent heat of vaporization.

Rapid and gentle drying of the plant sample is also considered an acceptable and acceptable method of fixation in some cases. With the skillful conduct of this process, deviations in the composition of the dry matter can be small. This results in protein denaturation and enzyme inactivation. As a rule, drying is carried out in drying cabinets (thermostats) or special drying chambers. The material dries much faster and more reliably if heated air circulates through the cabinet (chamber). The most suitable temperature for drying

stitching from 50 to 60°.

Dried material is better preserved in the dark and in the cold. Since many substances contained in plants are capable of self-oxidizing even in a dry state, it is recommended to store the dried material in tightly closed vessels (bottles with ground stoppers, desiccators, etc.), filled to the top with material so that there is not much air left in the vessels.

Freezing material. Plant material is very well preserved at temperatures from -20 to -30 °, provided that freezing occurs quickly enough (no more than 1 hour). The advantage of storing plant material in a frozen state is due to both the effect of cooling and the dehydration of the material due to the transition of water to a solid state. It should be borne in mind that when freezing

enzymes are inactivated only temporarily, and after thawing, enzymatic transformations can occur in the plant material.

Treatment of plants with organic solvents. As a quality

Boiling alcohol, acetone, ether, etc. can be used as fixing agents. Fixation of plant material by this method is carried out by lowering it into an appropriate solvent. However, with this method, not only the fixation of plant material occurs, but also the extraction of a number of substances. Therefore, such fixation can be used only when it is known in advance that the substances to be determined are not extracted by this solvent.

The plant samples dried after fixation are crushed with scissors and then in a mill. The crushed material is sifted through a sieve with a hole diameter of 1 mm. At the same time, nothing is thrown out of the sample, since by removing part of the material that did not pass through the sieve from the first sifting, we thereby change the quality of the average sample. Large particles are passed through the mill and sieve again. Residues on the sieve should be ground in a mortar.

An analytical sample is taken from the laboratory average sample prepared in this way. To do this, the plant material, distributed in a thin even layer on a sheet of glossy paper, is divided diagonally into four parts. Then two opposite triangles are removed, and the remaining mass is again distributed in a thin layer over the entire sheet of paper. Diagonals are drawn again and again two opposite triangles are removed. This is done until the amount of substance that is necessary for the analytical sample remains on the sheet. The selected analytical sample is transferred to glass jar with lapped stopper. In this state, it can be stored indefinitely. long time. The weight of an analytical sample depends on the amount and methodology of research and ranges from 50 to several hundred grams of plant material.

All analyzes of plant material should be carried out with two samples taken in parallel. Only similar results can confirm the correctness of the work done.

Plants should be handled in a dry and clean laboratory free of ammonia vapours, volatile acids and other compounds that could affect the quality of the sample.

The results of the analyzes can be calculated for both air-dry and absolutely dry samples of the substance. In the air-dry state, the amount of water in the material is in equilibrium with the water vapor in the air. This water is called hygroscopic, and the amount of it depends both on the plant and on the state of the air: the more humid the air, the more hygroscopic water in the plant material. To convert data to dry matter it is necessary to determine the amount of hygroscopic moisture in the sample.

DETERMINATION OF DRY MATTER AND HYGROSCOPIC MOISTURE IN AIR-DRY MATERIAL

In chemical analysis, the quantitative content of a particular constituent is calculated on a dry matter basis. Therefore, before analysis, the amount of moisture in the material is determined and thereby the amount of absolutely dry matter in it is determined.

Analysis progress. An analytical sample of the substance is spread in a thin layer on a sheet of glossy paper. Then, with a spatula, small pinches of the substance distributed on the sheet are taken from different places into a glass bottle, previously dried to a constant weight. The sample should be approximately 5 g. The weighing bottle together with the sample is weighed on an analytical balance and placed in a thermostat, the temperature inside of which is maintained at 100-1050. For the first time in a thermostat, an open bottle with a sample is kept for 4-6 hours. After this time, the bottle from the thermostat is transferred to a desiccator for cooling, after 20-30

minutes, the bottle is weighed. After that, the bottle is opened and again placed in a thermostat (at the same temperature) for 2 hours. Drying, cooling and weighing are repeated until the weighed bottle reaches a constant weight (the difference between the last two weighings must be less than 0.0003 g).

The percentage of water is calculated using the formula:

where: x is the percentage of water; c – weight of plant material before drying, g; c1 - weight of plant material after drying.

Equipment and utensils:

1) thermostat;

2) glass bottles.

Results Recording Form

Weight of box with		Weight of box with
		hinged on
up to	up to		Hinge
		after dry-
drying-	drying-		after vysu-
			sewing, g

DETERMINATION OF "RAW" ASH BY THE METHOD OF DRY ASHING

Ash is the residue obtained after burning and calcining organic matter. During combustion, carbon, hydrogen, nitrogen and partially oxygen escape and only non-volatile oxides remain.

The content and composition of the ash elements of plants depends on the species, growth and development of plants, and especially on the soil-climatic and agrotechnical conditions of their cultivation. The concentration of ash elements differs significantly in different fabrics and plant organs. Thus, the ash content in the leaves and herbaceous organs of plants is much higher than in the seeds. There is more ash in the leaves than in the stems,