Any method of analysis uses a certain analytical signal, which, under given conditions, is given by specific elementary objects (atoms, molecules, ions) that make up the substances under study.

An analytical signal provides both qualitative and quantitative information. For example, if precipitation reactions are used for analysis, qualitative information is obtained from the appearance or absence of a precipitate. Quantitative information is obtained from the weight of the sediment. When a substance emits light under certain conditions, qualitative information is obtained by the appearance of a signal (light emission) at a wavelength corresponding to the characteristic color, and quantitative information is obtained from the intensity of light radiation.

According to the origin of the analytical signal, methods of analytical chemistry can be classified into chemical, physical, and physicochemical methods.

IN chemical methods carry out a chemical reaction and measure either the mass of the product obtained - gravimetric (weight) methods, or the volume of the reagent used for interaction with the substance - titrimetric, gas volumetric (volumetric) methods.

Gas volumemetry (gas volumetric analysis) is based on the selective absorption of the constituent parts of a gas mixture in vessels filled with one or another absorber, followed by measurement of the decrease in gas volume using a burette. So, carbon dioxide is absorbed by a solution of potassium hydroxide, oxygen - by a solution of pyrogallol, carbon monoxide - by an ammonia solution of copper chloride. Gas volumemetry refers to express methods of analysis. It is widely used for the determination of carbonates in g.p. and minerals.

Chemical methods of analysis are widely used for the analysis of ores, rocks, minerals and other materials in the determination of components in them with a content of tenths to several tens of percent. Chemical analysis methods are characterized by high accuracy (analysis error is usually tenths of a percent). However, these methods are gradually being replaced by more rapid physicochemical and physical methods of analysis.

Physical Methods analyzes are based on the measurement of some physical property substances, which is a function of the composition. For example, refractometry is based on measuring the relative refractive indices of light. In an activation assay, the activity of isotopes, etc. is measured. Often, a chemical reaction is preliminarily carried out during the assay, and the concentration of the resulting product is determined by physical properties, for example, by the intensity of absorption of light radiation by the colored reaction product. Such methods of analysis are called physicochemical.

Physical methods of analysis are characterized by high productivity, low limits of detection of elements, objectivity of analysis results, high level automation. Physical methods of analysis are used in the analysis of rocks and minerals. For example, the atomic emission method determines tungsten in granites and slates, antimony, tin and lead in rocks and phosphates; atomic absorption method - magnesium and silicon in silicates; X-ray fluorescent - vanadium in ilmenite, magnesite, alumina; mass spectrometric - manganese in the lunar regolith; neutron activation - iron, zinc, antimony, silver, cobalt, selenium and scandium in oil; method of isotopic dilution - cobalt in silicate rocks.

Physical and physico-chemical methods are sometimes called instrumental, since these methods require the use of tools (equipment) specially adapted for carrying out the main stages of analysis and recording its results.

Physical and chemical methods analysis may include chemical transformations of the analyte, dissolution of the sample, concentration of the analyzed component, masking of interfering substances, and others. Unlike "classical" chemical methods of analysis, where the mass of a substance or its volume serves as an analytical signal, physicochemical methods of analysis use radiation intensity, current strength, electrical conductivity, and potential difference as an analytical signal.

Methods based on the study of the emission and absorption of electromagnetic radiation in various regions of the spectrum are of great practical importance. These include spectroscopy (for example, luminescent analysis, spectral analysis, nephelometry and turbidimetry, and others). Important physicochemical methods of analysis include electrochemical methods that use the measurement electrical properties substances (coulometry, potentiometry, etc.) as well as chromatography (eg gas chromatography, liquid chromatography, ion exchange chromatography, thin layer chromatography). Methods based on measuring the rates of chemical reactions (kinetic methods of analysis), thermal effects of reactions (thermometric titration), as well as on the separation of ions in a magnetic field (mass spectrometry) are successfully developed.

1. INTRODUCTION

2. CLASSIFICATION OF METHODS

3. ANALYTICAL SIGNAL

4.3. CHEMICAL METHODS

4.8. THERMAL METHODS

5. CONCLUSION

6. LIST OF USED LITERATURE

INTRODUCTION

Chemical analysis serves as a means of monitoring production and product quality in a number of industries National economy. Mineral exploration is based to varying degrees on the results of the analysis. Analysis is the main means of controlling contamination environment. Finding out the chemical composition of soils, fertilizers, feed and agricultural products is important for the normal functioning of the agro-industrial complex. Chemical analysis is indispensable in medical diagnostics and biotechnology. The development of many sciences depends on the level of chemical analysis, the equipment of the laboratory with methods, instruments and reagents.

The scientific basis of chemical analysis is analytical chemistry, a science that has been a part, and sometimes the main part, of chemistry for centuries.

Analytical chemistry- This is the science of determining the chemical composition of substances and partly their chemical structure. Methods of analytical chemistry allow answering questions about what a substance consists of, what components are included in its composition. These methods often make it possible to find out in what form a given component is present in a substance, for example, to determine the oxidation state of an element. Sometimes it is possible to estimate the spatial arrangement of components.

When developing methods, you often have to borrow ideas from related fields of science and adapt them to your goals. The task of analytical chemistry includes the development of the theoretical foundations of the methods, the establishment of the limits of their applicability, the assessment of metrological and other characteristics, the creation of methods for the analysis of various objects.

Methods and means of analysis are constantly changing: new approaches are involved, new principles and phenomena are used, often from distant areas of knowledge.

The analysis method is understood as a fairly universal and theoretically justified method for determining the composition, regardless of the component being determined and the object being analyzed. When they talk about the method of analysis, they mean the underlying principle, the quantitative expression of the relationship between the composition and any measured property; selected implementation techniques, including interference detection and elimination; devices for practical implementation and methods for processing measurement results. Analysis methodology is a detailed description of the analysis of a given object using the selected method.

There are three functions of analytical chemistry as a field of knowledge:

1. solution of general issues of analysis,

2. development of analytical methods,

3. solution of specific problems of analysis.

It can also be distinguished qualitative And quantitative analyses. The first decides the question of which components the analyzed object includes, the second gives information about the quantitative content of all or individual components.

2. CLASSIFICATION OF METHODS

All existing methods of analytical chemistry can be divided into methods of sampling, decomposition of samples, separation of components, detection (identification) and determination. There are hybrid methods that combine separation and definition. Detection and definition methods have much in common.

The methods of determination are of the greatest importance. They can be classified according to the nature of the measured property or the way the corresponding signal is registered. Methods of determination are divided into chemical , physical And biological. Chemical methods are based on chemical (including electrochemical) reactions. This includes methods called physicochemical. Physical methods are based on physical phenomena and processes, biological methods are based on the phenomenon of life.

The main requirements for analytical chemistry methods are: correctness and good reproducibility of results, low detection limit of the required components, selectivity, rapidity, ease of analysis, and the possibility of its automation.

When choosing an analysis method, it is necessary to clearly know the purpose of the analysis, the tasks that need to be solved, and evaluate the advantages and disadvantages of the available analysis methods.

3. ANALYTICAL SIGNAL

After the selection and preparation of the sample, the stage of chemical analysis begins, at which the component is detected or its amount is determined. For this purpose, they measure analytical signal. In most methods, the analytical signal is the average of measurements of a physical quantity at the final stage of analysis, functionally related to the content of the analyte.

If it is necessary to detect any component, it is usually fixed appearance analytical signal - the appearance of a precipitate, color, lines in the spectrum, etc. The appearance of an analytical signal must be reliably recorded. When determining the amount of a component, it is measured magnitude analytical signal - sediment mass, current strength, spectrum line intensity, etc.

4. METHODS OF ANALYTICAL CHEMISTRY

4.1. METHODS OF MASKING, SEPARATION AND CONCENTRATION

Masking.

Masking is inhibition or complete suppression chemical reaction in the presence of substances capable of changing its direction or speed. In this case, no new phase is formed. There are two types of masking - thermodynamic (equilibrium) and kinetic (non-equilibrium). In thermodynamic masking, conditions are created under which the conditional reaction constant is reduced to such an extent that the reaction proceeds insignificantly. The concentration of the masked component becomes insufficient to reliably fix the analytical signal. Kinetic masking is based on increasing the difference between the reaction rates of the masked and the analyte with the same reagent.

Separation and concentration.

The need for separation and concentration may be due to the following factors: the sample contains components that interfere with the determination; the concentration of the analyte is below the detection limit of the method; the components to be determined are unevenly distributed in the sample; there are no standard samples for calibrating instruments; the sample is highly toxic, radioactive and expensive.

Separation- this is an operation (process), as a result of which the components that make up the initial mixture are separated from one another.

concentration- this is an operation (process), as a result of which the ratio of the concentration or amount of microcomponents to the concentration or amount of the macrocomponent increases.

Precipitation and co-precipitation.

Precipitation is generally used to separate inorganic substances. Precipitation of microcomponents by organic reagents, and especially their co-precipitation, provide a high concentration factor. These methods are used in combination with methods of determination that are designed to obtain an analytical signal from solid samples.

Separation by precipitation is based on the different solubility of the compounds, mainly in aqueous solutions.

Co-precipitation is the distribution of a microcomponent between a solution and a precipitate.

Extraction.

Extraction is a physicochemical process of distributing a substance between two phases, most often between two immiscible liquids. It is also a process of mass transfer with chemical reactions.

Extraction methods are suitable for concentration, extraction of microcomponents or macrocomponents, individual and group isolation of components in the analysis of various industrial and natural objects. The method is simple and fast to perform, provides high efficiency of separation and concentration, and is compatible with various methods of determination. Extraction allows you to study the state of substances in solution under various conditions, to determine the physico-chemical characteristics.

Sorption.

Sorption is well used for separation and concentration of substances. Sorption methods usually provide good separation selectivity and high values ​​of concentration factors.

Sorption- the process of absorption of gases, vapors and dissolved substances by solid or liquid absorbers on a solid carrier (sorbents).

Electrolytic separation and cementation.

The most common method of electoral separation, in which the separated or concentrated substance is isolated on solid electrodes in the elemental state or in the form of some kind of compound. Electrolytic isolation (electrolysis) based on precipitation electric shock at controlled potential. The most common variant of cathodic deposition of metals. The electrode material can be carbon, platinum, silver, copper, tungsten, etc.

electrophoresis is based on differences in the speeds of movement of particles of different charges, shapes and sizes in an electric field. The speed of movement depends on the charge, field strength and particle radius. There are two types of electrophoresis: frontal (simple) and zone (on a carrier). In the first case, a small volume of a solution containing the components to be separated is placed in a tube with an electrolyte solution. In the second case, the movement occurs in a stabilizing medium that keeps the particles in place after the electric field is turned off.

Method grouting consists in the reduction of components (usually small amounts) on metals with sufficiently negative potentials or almagamas of electronegative metals. During cementation, two processes occur simultaneously: cathodic (separation of the component) and anodic (dissolution of the cementing metal).

Evaporation methods.

Methods distillation based on the different volatility of substances. The substance passes from a liquid state to a gaseous state, and then condenses, forming again a liquid or sometimes a solid phase.

Simple distillation (evaporation)– single-stage separation and concentration process. Evaporation removes substances that are in the form of ready-made volatile compounds. These can be macrocomponents and microcomponents, the distillation of the latter is used less frequently.

Sublimation (sublimation)- transfer of substance from solid state into gaseous and subsequent precipitation in solid form (bypassing the liquid phase). Separation by sublimation is usually resorted to if the components to be separated are difficult to melt or are difficult to dissolve.

Controlled crystallization.

When a solution, melt or gas is cooled, solid phase nuclei are formed - crystallization, which can be uncontrolled (bulk) and controlled. With uncontrolled crystallization, crystals arise spontaneously throughout the volume. With controlled crystallization, the process is set by external conditions (temperature, direction of phase movement, etc.).

There are two types of controlled crystallization: directional crystallization(V given direction) And zone melting(movement of a liquid zone in a solid body in a certain direction).

With directional crystallization, one interface appears between a solid and a liquid - the crystallization front. There are two boundaries in zone melting: the crystallization front and the melting front.

4.2. CHROMATOGRAPHIC METHODS

Chromatography is the most commonly used analytical method. The latest chromatographic methods can determine gaseous, liquid and solid substances with molecular weights from units to 10 6 . These can be hydrogen isotopes, metal ions, synthetic polymers, proteins, etc. With the help of chromatography, extensive information on the structure and properties of organic compounds many classes.

Chromatography- This is a physico-chemical method of separation of substances, based on the distribution of components between two phases - stationary and mobile. The stationary phase (stationary) is usually a solid (often referred to as a sorbent) or a liquid film deposited on a solid. The mobile phase is a liquid or gas flowing through the stationary phase.

The method allows separating a multicomponent mixture, identifying the components and determining its quantitative composition.

Chromatographic methods are classified according to the following criteria:

a) according to the state of aggregation of the mixture, in which it is separated into components - gas, liquid and gas-liquid chromatography;

b) according to the separation mechanism - adsorption, distribution, ion-exchange, sedimentary, redox, adsorption-complexation chromatography;

c) according to the form of the chromatographic process - column, capillary, planar (paper, thin-layer and membrane).

4.3. CHEMICAL METHODS

Chemical methods of detection and determination are based on chemical reactions of three types: acid-base, redox, and complex formation. Sometimes they are accompanied by a change in the aggregate state of the components. The most important among chemical methods are gravimetric and titrimetric. These analytical methods are called classical. The criteria for the suitability of a chemical reaction as the basis of an analytical method in most cases are completeness and high speed.

gravimetric methods.

Gravimetric analysis consists in isolating a substance in its pure form and weighing it. Most often, such isolation is carried out by precipitation. A less commonly determined component is isolated as a volatile compound (distillation methods). In some cases, gravimetry is the best way to solve an analytical problem. This is an absolute (reference) method.

The disadvantage of gravimetric methods is the duration of the determination, especially in serial analyzes. a large number samples, as well as non-selectivity - precipitating reagents, with a few exceptions, are rarely specific. Therefore, preliminary separations are often necessary.

Mass is the analytical signal in gravimetry.

titrimetric methods.

The titrimetric method of quantitative chemical analysis is a method based on measuring the amount of reagent B spent on the reaction with the component A being determined. In practice, it is most convenient to add the reagent in the form of a solution of exactly known concentration. In this version, titration is the process of continuously adding a controlled amount of a reagent solution of exactly known concentration (titran) to a solution of the component to be determined.

In titrimetry, three titration methods are used: forward, reverse, and substituent titration.

direct titration- this is the titration of a solution of the analyte A directly with a solution of titran B. It is used if the reaction between A and B proceeds quickly.

Back titration consists in adding to the analyte A an excess of a precisely known amount of standard solution B and, after completion of the reaction between them, titration of the remaining amount of B with a solution of titran B'. This method is used in cases where the reaction between A and B is not fast enough, or there is no suitable indicator to fix the reaction equivalence point.

Substituent titration consists in titration with titrant B not of a determined amount of substance A, but of an equivalent amount of substituent A ', resulting from a preliminary reaction between a determined substance A and some reagent. This method of titration is usually used in cases where it is impossible to carry out direct titration.

Kinetic methods.

Kinetic methods are based on the dependence of the rate of a chemical reaction on the concentration of the reactants, and in the case of catalytic reactions, on the concentration of the catalyst. The analytical signal in kinetic methods is the rate of the process or a quantity proportional to it.

The reaction underlying the kinetic method is called indicator. A substance whose change in concentration is used to judge the rate of an indicator process is indicator.

biochemical methods.

Among modern methods chemical analysis an important place is occupied by biochemical methods. Biochemical methods include methods based on the use of processes involving biological components (enzymes, antibodies, etc.). In this case, the analytical signal is most often either the initial rate of the process or the final concentration of one of the reaction products, determined by any instrumental method.

Enzymatic Methods based on the use of reactions catalyzed by enzymes - biological catalysts, characterized by high activity and selectivity of action.

Immunochemical methods analyzes are based on the specific binding of the determined compound - antigen by the corresponding antibodies. The immunochemical reaction in solution between antibodies and antigens is a complex process that occurs in several stages.

4.4. ELECTROCHEMICAL METHODS

Electrochemical methods of analysis and research are based on the study and use of processes occurring on the electrode surface or in the near-electrode space. Any electrical parameter (potential, current strength, resistance, etc.) that is functionally related to the concentration of the analyzed solution and can be correctly measured can serve as an analytical signal.

There are direct and indirect electrochemical methods. In direct methods, the dependence of the current strength (potential, etc.) on the concentration of the analyte is used. In indirect methods, the current strength (potential, etc.) is measured in order to find the end point of the titration of the analyte with a suitable titrant, i.e. use the dependence of the measured parameter on the volume of the titrant.

For any kind of electrochemical measurements, an electrochemical circuit or an electrochemical cell is required, the component of which is the analyzed solution.

There are various ways to classify electrochemical methods, from very simple to very complex, involving consideration of the details of the electrode processes.

4.5. SPECTROSCOPIC METHODS

Spectroscopic methods of analysis include physical methods based on the interaction of electromagnetic radiation with matter. This interaction leads to various energy transitions, which are registered experimentally in the form of radiation absorption, reflection and scattering of electromagnetic radiation.

4.6. MASS SPECTROMETRIC METHODS

The mass spectrometric method of analysis is based on the ionization of atoms and molecules of the emitted substance and the subsequent separation of the resulting ions in space or time.

The most important application of mass spectrometry has been to identify and establish the structure of organic compounds. Molecular analysis of complex mixtures of organic compounds should be carried out after their chromatographic separation.

4.7. METHODS OF ANALYSIS BASED ON RADIOACTIVITY

Methods of analysis based on radioactivity arose in the era of the development of nuclear physics, radiochemistry, and atomic technology, and are now successfully used in various analyzes, including in industry and the geological service. These methods are very numerous and varied. Four main groups can be distinguished: radioactive analysis; isotope dilution methods and other radiotracer methods; methods based on the absorption and scattering of radiation; purely radiometric methods. The most widespread radioactive method. This method appeared after the discovery of artificial radioactivity and is based on the formation of radioactive isotopes of the element being determined by irradiating the sample with nuclear or g-particles and recording the artificial radioactivity obtained during activation.

4.8. THERMAL METHODS

Thermal methods of analysis are based on the interaction of matter with thermal energy. Thermal effects, which are the cause or effect of chemical reactions, are most widely used in analytical chemistry. To a lesser extent, methods based on the release or absorption of heat as a result of physical processes are used. These are processes associated with the transition of a substance from one modification to another, with a change in the state of aggregation and other changes in intermolecular interaction, for example, occurring during dissolution or dilution. The table shows the most common methods of thermal analysis.

Thermal methods are successfully used for the analysis of metallurgical materials, minerals, silicates, as well as polymers, for the phase analysis of soils, and for determining the moisture content in samples.

4.9. BIOLOGICAL METHODS OF ANALYSIS

Biological methods of analysis are based on the fact that for vital activity - growth, reproduction and, in general, the normal functioning of living beings, an environment of a strictly defined chemical composition is necessary. When this composition changes, for example, when a component is excluded from the medium or an additional (determined) compound is introduced, the body, after some time, sometimes almost immediately, gives an appropriate response signal. Establishing a connection between the nature or intensity of the body's response signal and the amount of a component introduced into the environment or excluded from the environment serves to detect and determine it.

Analytical indicators in biological methods are various living organisms, their organs and tissues, physiological functions, etc. Microorganisms, invertebrates, vertebrates, as well as plants can act as indicator organisms.

5. CONCLUSION

The significance of analytical chemistry is determined by the need of society for analytical results, in establishing the qualitative and quantitative composition of substances, the level of development of society, the social need for the results of analysis, as well as the level of development of analytical chemistry itself.

A quote from N.A. Menshutkin’s textbook on analytical chemistry, 1897: “Having presented the entire course of classes in analytical chemistry in the form of problems, the solution of which is left to the student, we must point out that for such a solution of problems, analytical chemistry will give a strictly defined path. This certainty (systematic solving problems of analytical chemistry) is of great pedagogical importance. At the same time, the student learns to apply the properties of compounds to solving problems, derive reaction conditions, and combine them. This whole series of mental processes can be expressed as follows: analytical chemistry teaches chemical thinking. The achievement of the latter seems to be the most important for practical studies in analytical chemistry.

LIST OF USED LITERATURE

1. K.M. Olshanova, S.K. Piskareva, K.M. Barashkov "Analytical Chemistry", Moscow, "Chemistry", 1980

2. "Analytical chemistry. Chemical methods of analysis”, Moscow, “Chemistry”, 1993

3. “Fundamentals of Analytical Chemistry. Book 1", Moscow, " graduate School", 1999

4. “Fundamentals of Analytical Chemistry. Book 2, Moscow, Higher School, 1999

All existing methods of analytical chemistry can be divided into methods of sampling, decomposition of samples, separation of components, detection (identification) and determination.

Almost all methods are based on the relationship between the composition of a substance and its properties. To detect a component or its amount, measure analytical signal.

Analytical signal is the average of the measurements of the physical quantity at the final stage of the analysis. The analytical signal is functionally related to the content of the determined component. This may be the current strength, EMF of the system, optical density, radiation intensity, etc.

If it is necessary to detect any component, the appearance of an analytical signal is usually recorded - the appearance of a precipitate, a color, a line in the spectrum, etc. The appearance of an analytical signal must be reliably recorded. At a certain amount of the component, the magnitude of the analytical signal is measured: the mass of the deposit, the current strength, the intensity of the lines of the spectrum, etc. Then the content of the component is calculated using the functional dependence analytical signal - content: y=f(c), which is established by calculation or experience and can be presented in the form of a formula, table or graph.

In analytical chemistry, there are chemical, physical and physico-chemical methods of analysis.

In chemical methods of analysis, the element or ion being determined is converted into a compound that has one or another characteristic property, on the basis of which it can be established that this particular compound was formed.

Chemical Methods analysis have a specific scope. Also, the speed of performing analyzes using chemical methods does not always satisfy the needs of production, where it is very important to get analyzes in a timely manner, while it is still possible to regulate the technological process. Therefore, along with chemical methods, physical and physico-chemical methods of analysis are becoming more widespread.

Physical Methods analyzes are based on the measurement of some

a system parameter that is a function of composition, such as emission absorption spectra, electrical or thermal conductivity, potential of an electrode immersed in a solution, permittivity, refractive index, nuclear magnetic resonance, etc.

Physical analysis methods make it possible to solve problems that cannot be resolved by chemical analysis methods.

For the analysis of substances, physicochemical methods of analysis are widely used, based on chemical reactions, the course of which is accompanied by a change in the physical properties of the analyzed system, for example, its color, color intensity, transparency, thermal and electrical conductivity, etc.

Physical and chemical methods of analysis are characterized by high sensitivity and rapid execution, make it possible to automate chemical-analytical determinations and are indispensable in the analysis of small amounts of substances.

It should be noted that it is not always possible to draw a strict boundary between physical and physicochemical methods of analysis. Sometimes they are combined under common name"instrumental" methods, because to perform certain measurements, instruments are required that allow one to measure with great accuracy the values ​​of certain parameters that characterize certain properties of a substance.

These methods of analysis are used in the presence of a relationship between the measured physical properties in-in and their qualitative and quantitative composition. Since various instruments (instruments) are used to measure physical properties, these methods are called instrumental. Classification of physical and physico-chemical methods of analysis. Based on taking into account the measured physical and physico-chemical sv-v-va or the system under study. Optical methods are based on the measurement of optical St-in-in. Chromatographic on use ability various in-in to selective sorption. Electrochemical methods are based on the measurement of electrochemical properties in the system. Radiometric based on the measurement of radioactive sv-in in-in. Thermal on the measurement of the thermal effects of the relevant processes. Mass spectrometry in the study of ionized fragments ("fragments") in-in. Ultrasonic, magnetochemical, pycnometric, etc. Advantages of instrumental methods of analysis: low detection limit 1 -10 -9 µg; low limiting concentration, up to 10 -12 g / ml of the determined in-va; high sensitivity, formally determined by the value of the tangent of the slope of the corresponding calibration curve, which graphically reflects the dependence of the measured physical parameter, which is usually plotted along the ordinate axis, on the quantity or concentration of the determined substance (abscissa axis). The greater the tangent of the slope of the curve to the x-axis, the more sensitive the method, which means the following: to obtain the same “response” - a change in physical property - a smaller change in the concentration or amount of the measured substance is required. The advantages include the high selectivity (selectivity) of the methods, i.e., the constituent components of mixtures can be determined without separating and isolating these components; short duration of analysis, the possibility of their automation and computerization. Disadvantages: hardware complexity and high cost; greater error (5 -20%) than in classical chemical analysis (0.1 -0.5%); worse reproducibility. Optical methods of analysis are based on the measurement of optical properties in the islands (emission, absorption, scattering, reflection, refraction, polarization of light), which manifest themselves during the interaction of electromagnetic radiation with the island.

Classification according to the objects under study: atomic and molecular spectral analysis. By the nature of the interaction of electromagnetic radiation with in-ohm. In this case, the following methods are distinguished. Atomic absorption analysis, which is based on the measurement of the absorption of monochromatic radiation by atoms of the substance being determined in the gas phase after the atomization of the substance. Emission spectral analysis - measurement of the intensity of light emitted in th (most often atoms or ions) during its energy excitation, for example, in an electric discharge plasma. Flame photometry - the use of a gas flame as a source of energy excitation of radiation. Nephelometry - measurement of light scattering by light particles of a dispersed system (environment). Turbidimetric analysis - measurement of the attenuation of the intensity of radiation during its passage through a dispersed medium. Refractometric analysis measurement of light refraction indices in-in. Polarimetric analysis is the measurement of the magnitude of optical rotation - the angle of rotation of the plane of polarization of light by optically active objects. The following methods are classified according to the region of the electromagnetic spectrum used: spectroscopy (spectrophotometry) in the UVI region of the spectrum, i.e., in the nearest ultraviolet region of the spectrum - in the wavelength range of 200 - 400 nm and in the visible region - in the wavelength range of 400 - 700 nm. Infrared spectroscopy, which studies a section of the electromagnetic spectrum in the range of 0.76 - 1000 μm (1 μm = 10 -6 m), less often X-ray and microwave spectroscopy. By the nature of energy transitions in various spectra - electronic (change in the energy of the electronic states of atoms, ions, radicals, molecules, crystals in the UVI region); vibrational (when changing the energy of vibrational states of 2- and polyatomic ions, radicals, molecules, as well as liquid and solid phases in the IR region); rotational also in the IR and microwave region. That. The interaction between molecules and electromagnetic radiation lies in the fact that by absorbing electromagnetic radiation, the molecules pass into an excited state. In this case, an important role is played by energy, i.e., the wavelength of the absorbed radiation.

So, in x-rays, the wavelength of which is 0.05 - 5 nm, the process of excitation of internal electrons in atoms and molecules occurs; in ultraviolet rays (5 - 400 nm) the process of excitation of external electrons in atoms and molecules occurs; visible light (400 - 700 nm) excitation of external electrons in conjugated p-electronic systems; infrared radiation (700 nm - 500 microns) is the process of excitation of vibrations of molecules; microwaves (500 microns - 30 cm) the process of excitation of the rotation of molecules; radio waves (more than 30 cm) the process of excitation of spin transitions in atomic nuclei (nuclear magnetic resonance). The absorption of radiations makes it possible to measure and record them in spectrometry. In this case, the incident radiation is divided into reference and measured at the same intensity. The measured radiation passes through the sample; when absorption occurs, the intensity changes. When absorbing the energy of electromagnetic radiation, particles in the islands (atoms, molecules, ions) increase their energy, i.e., they pass into a higher energy state. Electronic, vibrational, rotational energy states of the particles in the islands can only change discretely, by a strictly defined amount. For each particle there is an individual set of energy states - energy levels (terms), for example, electronic energy levels. Electronic energy levels of molecules and polyatomic ions have a fine structure - vibrational sublevels; therefore, vibrational transitions also take place simultaneously with purely electronic transitions.

Each electronic (electronic-vibrational) transition from a lower energy level to a higher lying electronic level corresponds to a band in the electronic absorption spectrum. Since the difference between the electronic levels for each particle (atom, ion, molecule) is strictly defined, the position of the band in the electronic absorption spectrum corresponding to one or another electronic transition is also strictly defined, i.e. the wavelength (frequency, wave number) absorption band maximum. Differences in intensity are measured by a detector and recorded on a recorder in the form of a signal (peak), page 318, chemistry, schoolchild and student reference book, spectrometer scheme. Ultraviolet spectroscopy and absorption spectroscopy in the visible region. Absorption of electromagnetic radiation from the ultraviolet and visible parts of the spectrum; excites transitions of electrons in molecules from occupied to unoccupied energy levels. The greater the difference in energy between energy levels, the greater the energy, i.e. shorter wavelength, must have radiation. The part of the molecule that largely determines the absorption of light is called the chromophore (literally, color carriers) - these are atomic groups that affect the absorption of light by the molecule, especially conjugated and aromatic p-electron systems.

Structural elements of chromophores are mainly involved in the absorption of a quantum of light energy, which leads to the appearance of bands in a relatively narrow region of the absorption spectrum of compounds. The region from 200 to 700 nm is of practical importance for determining the structure of organic molecules. Quantitative measurement: along with the position of the absorption maximum, the value of extinction (attenuation) of radiation, i.e., the intensity of its absorption, is important for analysis. In accordance with the law of Lambert - Beer E \u003d lgI 0 / I \u003d ecd, E - extinction, I 0 - intensity of incident light, I - intensity of transmitted light, e - molar extinction coefficient, cm 2 / mol, c - concentration, mol / l, d - thickness of the sample layer, cm. Extinction depends on the concentration of the absorbing substance. Absorption analysis methods: colorimetry, photoelectrocolorimetry, spectrometry. Colorimetry is the simplest and oldest method of analysis, based on a visual comparison of the color of liquids (determination of soil pH on an Alyamovsky device) - the simplest method of comparison with a series of reference p-s. 3 methods of colorimetry are widely used: standard series method (scale method), color equalization method and dilution method. Glass colorimetric test tubes, glass burettes, colorimeters, photometers are used. The scale method is the determination of pH on an Alyamovsky instrument, i.e. a series of test tubes with different concentrations in the islands and different in terms of changing the intensity of the color of the solution or reference solutions. Photocolorimetry - the method is based on measuring the intensity of a non-monochromatic light flux that has passed through the analyzed solution using photocells.

The luminous flux from the radiation source (incandescent lamp) passes through a light filter that transmits radiation only in a certain wavelength range, through a cuvette with the analyzed p-ohm and enters a photocell that converts light energy into photocurrent recorded by an appropriate device. The greater the light absorption of the analyzed solution (i.e., the higher its optical density), the lower the energy of the light flux falling on the photocell. FECs are supplied with n-mi filters that have a maximum light transmission at different wavelengths. In the presence of 2 photocells, 2 light fluxes are measured, one through the analyzed solution, the other through comparison solution. The concentration of the studied substance is found according to the calibration curve.

Electrochemical methods of analysis are based on electrode reactions and on the transfer of electricity through solutions. In quantitative analysis, the dependence of the values ​​of the measured parameters of electrochemical processes (difference in electrical potentials, current, amount of electricity) on the content of the determined substance in the solution involved in this electrochemical process is used. Electrochemical processes are those processes that are accompanied by the simultaneous occurrence of chemical reactions and a change in the electrical properties of the system, which in such cases can be called an electrochemical system. Basic Principles of Potentiometry

As the name of the method implies, the potential is measured in it. To clarify what kind of potential and why it arises, consider a system consisting of a metal plate and a solution containing ions of the same metal (electrolyte) in contact with it (Fig. 1). Such a system is called an electrode. Any system tends to a state that corresponds to the minimum of its internal energy. Therefore, at the first moment after the metal is immersed in the solution, processes begin to occur at the phase boundary, leading to a decrease in the internal energy of the system. Let us assume that the ionized state of the metal atom is energetically more “favorable” than the neutral state (the opposite is also possible). Then, at the first moment of time, the metal atoms will pass from the surface layer of the plate into the solution, leaving their valence electrons in it. In this case, the surface of the plate acquires a negative charge, and this charge increases with the increase in the number of metal atoms that have passed into the solution in the form of ions. The electrostatic forces of attraction of unlike charges (negatively charged electrons in the plate and positive metal ions in solution) do not allow these charges to move away from the phase boundary, and also cause the reverse process of metal ions to pass from solution to the metal phase and restore them there. When the rates of the forward and reverse processes become the same, equilibrium occurs. The equilibrium state of the system is characterized by the separation of charges at the phase boundary, i.e., a “jump” of the potential appears. It should be noted that the described mechanism of the occurrence of the electrode potential is not the only one; in real systems, many other processes also occur, leading to the formation of a “jump” of potentials at the interface. In addition, a potential “jump” can occur at the phase boundary not only when the electrolyte comes into contact with a metal, but also when the electrolyte comes into contact with other materials, such as semiconductors, ion exchange resins, glasses, etc.

In this case, ions whose concentration affects the potential of the electrode are called potential-determining. The electrode potential depends on the nature of the material in contact with the electrolyte, the concentration of potential-determining ions in the solution, and the temperature. This potential is measured relative to another electrode whose potential is constant. Thus, having established this relationship, it is possible to use it in analytical practice to determine the concentration of ions in a solution. In this case, the electrode, the potential of which is measured, is called the measuring one, and the electrode, relative to which the measurements are made, is called the auxiliary or reference electrode. The constancy of the potential of the reference electrodes is achieved by the constancy of the concentration of potential-determining ions in its electrolyte (electrolyte No. 1). The composition of electrolyte #2 may vary. To prevent mixing of two different electrolytes, they are separated by an ion-permeable membrane. The potential of the measuring electrode is taken equal to the measured emf of the reduced electrochemical system. Using solutions of a known composition as electrolyte No. 2, it is possible to establish the dependence of the potential of the measuring electrode on the concentration of potential-determining ions. This dependence can later be used in the analysis of a solution of unknown concentration.

To standardize the potential scale, a standard hydrogen electrode was adopted as a reference electrode, the potential of which was assumed to be zero at any temperature. However, in conventional measurements, the hydrogen electrode is rarely used because of its bulkiness. In everyday practice, other simpler reference electrodes are used, the potential of which relative to the hydrogen electrode is determined. Therefore, if necessary, the result of the potential measurement carried out with respect to such electrodes can be recalculated with respect to the hydrogen electrode. The most widely used are silver chloride and calomel reference electrodes. The potential difference between the measuring electrode and the reference electrode is a measure of the concentration of the ions to be determined.

The electrode function can be described using linear equation Nernst:

E \u003d E 0 + 2.3 RT / nF * lg a,

where E is the potential difference between the measuring electrode and the reference electrode, mV; E 0 - constant, depending mainly on the properties of the reference electrode (standard electrode potential), mV; R - gas constant, J * mol -1 * K -1. ; n is the charge of the ion, taking into account its sign; F - Faraday number, C/mol; T - absolute temperature, 0 K; the term 2.3 RT/nF included in the Nernst equation at 25 0 C is 59.16 mV for singly charged ions. The method without imposing an external (extraneous) potential is classified as a method based on taking into account the nature of the source of electrical energy in the system. In this method, the source of el.en. the electrochemical system itself serves, which is galvanic cell(galvanic circuit) - potentiometric methods. EMF and electrode potentials in such a system depend on the soda of the determined substance in the solution. The electrochemical cell includes 2 electrodes - indicator and reference electrode. The value of the EMF generated in the cell is equal to the potential difference of these 2 electrodes.

The potential of the reference electrode under the conditions of the potentiometric determination remains constant, then the EMF depends only on the potential of the indicator electrode, that is, on the activities (concentrations) of certain ions in the solution. This is the basis for the potentiometric determination of the concentration of a given substance in the anal-th solution. Both direct potentiometry and potentiometric titration are used. When determining the pH of the solutions as indicator electrodes, the potential of which depends on the concentration of hydrogen ions is used: glass, hydrogen, quinhydrone (redox electrode in the form of a platinum wire immersed in HC1 solution, saturated with quinhydrone - an equimolecular compound quinone with hydroquinone) and some others. Membrane or ion-selective electrodes have a real potential, depending on the activity of those ions in the solution, which are sorbed by the electrode membrane (solid or liquid), the method is called ionometry.

Spectrophotometers are devices that make it possible to measure the light absorption of samples in beams of light narrow in spectral composition (monochromatic light). Spectrophotometers make it possible to decompose White light into a continuous spectrum, select a narrow wavelength range from this spectrum (1 - 20 nm width of the selected spectrum band), pass an isolated light beam through the analyzed solution and measure the intensity of this beam with high accuracy. The absorption of light by the colored solution in the solution is measured by comparing it with the absorption zero solution. The spectrophotometer combines two devices: a monochromator for obtaining a monochromatic light flux and a photoelectric photometer for measuring light intensity. The monochromator consists of a light source, a dispersing device (decomposing white light into a spectrum) and a device for regulating the magnitude of the wavelength interval of the light beam incident on the solution.

Of the various physicochemical and physical methods of analysis, 2 groups of methods are of greatest importance: 1 - methods based on the study of the spectral characteristics of the island; 2 - methods based on the study of physico-chemical parameters. Spectral methods are based on the phenomena that occur when a substance interacts with various types energy (electromagnetic radiation, thermal energy, electrical energy, etc.). The main types of interaction in-va with radiant energy include absorption and emission (emission) of radiation. The nature of the phenomena due to absorption or emission is in principle the same. When radiation interacts with matter, its particles (atoms of the molecule) pass into an excited state. After some time (10 -8 s), the particles return to the ground state, emitting excess energy in the form of electromagnetic radiation. These processes are associated with electronic transitions in an atom or molecule.

Electromagnetic radiation can be characterized by wavelength or frequency n, which are interconnected by the ratio n=s/l, where c is the speed of light in vacuum (2.29810 8 m/s). The totality of all wavelengths (frequencies) of electromagnetic radiation makes up the electromagnetic spectrum from r-rays (short-wave region, photons have high energy) to the visible region of the spectrum (400 - 700 nm) and radio waves (long wavelength region, low energy photons).

In practice, one deals with radiation characterized by a certain interval of wavelengths (frequencies), i.e., with a certain section of the spectrum (or, as they say, with a radiation band). Often, for analytical purposes, monochromatic light is also used (a light flux in which electromagnetic waves have one wavelength). Selective absorption by atoms and molecules of radiation with certain wavelengths leads to the fact that each in-in is characterized by individual spectral characteristics.

For analytical purposes, both the absorption of radiation by atoms and molecules (respectively, atomic absorption spectroscopy) and the emission of radiation by atoms and molecules (emission spectroscopy and luminescence) are used.

Spectrophotometry is based on the selective absorption of electromagnetic radiation in-vom. By measuring the absorption in-tion of radiation of various wavelengths, one can obtain an absorption spectrum, i.e., the dependence of absorption on the wavelength of the incident light. The absorption spectrum is a qualitative characteristic of the island. A quantitative characteristic is the amount of absorbed energy or the optical density of the solution, which depends on the concentration of the absorbing substance according to the Bouguer-Lambert-Beer law: D \u003d eIs, where D is the optical density, i is the layer thickness; с - concentration, mol/l; e is the molar absorption coefficient (e = D at I=1 cm and c=1 mol/l). The value of e serves as a sensitivity characteristic: the larger the value of e, the smaller the amount of v-va can be determined. Many substances (especially organic ones) intensively absorb radiation in the UV and visible regions, which makes it possible to directly determine them. Most ions, on the contrary, weakly absorb radiation in the visible region of the spectrum (е? 10…1000), so they are usually transferred to other, more intensely absorbing compounds, and then measurements are taken. To measure absorption (optical density), two types of spectral instruments are used: photoelectrocolorimeters (with coarse monochromatization) and spectrophotometers (with finer monochromatization). The most common is the photometric method of analysis, quantitative determinations in which are based on the Bouguer-Lambert-Beer law. The main methods of photometric measurements are: the method of molar light absorption coefficient, the calibration curve method, the standard method (comparison method), the additive method. In the method of molar light absorption coefficient, the optical density D of the investigated solution is measured and, using the known value of the molar light absorption coefficient e, the concentration of the absorbing substance in the solution is calculated: c \u003d D / (e I). In the calibration curve method, a series of standard solutions are prepared with a known concentration value from the component to be determined and their optical density value D is determined.

According to the data obtained, a calibration graph is built - the dependence of the optical density of the solution on the concentration of the in-va: D = f (c). According to the Bucher-Lambert-Beer law, the graph is a straight line. Then the optical density D of the test solution is measured and the concentration of the analyte is determined from the calibration curve. The method of comparison (standards) is based on a comparison of the optical density of the standard and test solutions:

D st \u003d e * I * s st and D x \u003d e * I * s x,

whence D x / D st \u003d e * I * s x / e * I * s st and c x \u003d s st * D x / D st. In the addition method, the values ​​of the optical density of the test solution are compared with the same solution with the addition (with a) of a known amount of the component to be determined. Based on the results of the determinations, the concentration of the substance in the test solution is calculated: D x \u003d e * I * c x and D x + a \u003d e * I * (c x + c a), whence D x / D x + a \u003d e * I * c x / e * I * (c x + c a) and c x \u003d c a * D x / D x + a - D x. .

Atomic absorption spectroscopy is based on the selective absorption of radiation by atoms. To transfer the substance to the atomic state, the sample solution is injected into the flame or heated in a special cuvette. As a result, the solvent volatilizes or burns out, and the solid matter is atomized. Most of the atoms remain in an unexcited state, and only a small part is excited with subsequent emission of radiation. The set of lines corresponding to the wavelengths of the absorbed radiation, i.e., the spectrum, is a qualitative characteristic, and the intensity of these lines is, respectively, a quantitative characteristic of the island.

Atomic emission spectroscopy is based on measuring the intensity of light emitted by excited atoms. Excitation sources can be a flame, a spark discharge, an electric arc, etc. To obtain emission spectra, a sample in the form of a powder or solution is introduced into the excitation source, where the substance passes into a gaseous state or partially decays into atoms and simple (by composition) molecules. A qualitative characteristic of a substance is its spectrum (i.e., a set of lines in the emission spectrum), and a quantitative characteristic is the intensity of these lines.

Luminescence is based on the emission of radiation by excited molecules (atoms, ions) during their transition to the ground state. In this case, sources of excitation can be ultraviolet and visible radiation, cathode rays, the energy of a chemical reaction, etc. The energy of radiation (luminescence) is always less than the absorbed energy, since part of the absorbed energy is converted into heat even before the emission begins. Therefore, luminescent emission always has a shorter wavelength than the wavelength of the light absorbed during excitation. Luminescence can be used both to detect substances (by wavelength) and to quantify them (by radiation intensity). Electrochemical methods of analysis are based on the interaction of matter with an electric current. The processes proceeding in this case are localized either on the electrodes or in the near-electrode space. Most methods are of the first of these types. Potentiometry. An electrode process is a heterogeneous reaction in which a charged particle (ion, electron) is transferred through the phase boundary. As a result of such a transfer, a potential difference arises on the surface of the electrode, due to the formation of a double electric layer. Like any process, the electrode reaction eventually comes to equilibrium, and an equilibrium potential is established on the electrode.

Measuring the values ​​of equilibrium electrode potentials is the task of the potentiometric method of analysis. Measurements are carried out in an electrochemical cell consisting of 2 half-cells. One of them contains an indicator electrode (the potential of which depends on the concentration of the ions to be determined in the solution in accordance with the Nernst equation), and the other a reference electrode (the potential of which is constant and does not depend on the composition of the solution). The method can be implemented as direct potentiometry or as potentiometric titration. In the first case, the potential of the indicator electrode in the analyzed solution is measured relative to the reference electrode, and the concentration of the ion to be determined is calculated using the Nernst equation. In the variant of potentiometric titration, the ion to be determined is titrated with a suitable reagent, while simultaneously monitoring the change in the potential of the indicator electrode. Based on the data obtained, a titration curve is built (dependence of the indicator electrode potential on the volume of added titrant). On the curve near the equivalence point, there is a sharp change in the potential value (potential jump) of the indicator electrode, which makes it possible to calculate the content of the ion being determined in the solution. Electrode processes are very diverse. In general, they can be classified into 2 large groups: processes that occur with the transfer of electrons (i.e., the actual electrochemical processes), and processes associated with the transfer of ions (in this case, the electrode is inherent ionic conductivity). In the latter case, we are talking about the so-called ion-selective membrane electrodes, which are widely used at present. The potential of such an electrode in a solution containing ions to be determined depends on their concentration according to the Nernst equation. The glass electrode used in pH-metry also belongs to the same type of electrodes. The possibility of creating a large number of membrane electrodes with high selectivity to certain ions has singled out this area of ​​potentiometric analysis into an independent branch - ionometry.

Polarography. During the passage of current in an electrochemical cell, a deviation of the values ​​of the electrode potentials from their equilibrium values ​​is observed. For a number of reasons, the so-called electrode polarization occurs. The phenomenon of polarization that occurs during electrolysis on an electrode with a small surface underlies this method of analysis. In this method, an increasing potential difference is applied to the electrodes dipped into the test solution. With a small potential difference, there is practically no current through the solution (the so-called residual current). With an increase in the potential difference to a value sufficient for the decomposition of the electrolyte, the current increases sharply. This potential difference is called the decomposition potential. By measuring the dependence of the strength of the current passing through the solution on the magnitude of the applied voltage, one can construct the so-called. current-voltage curve, which allows you to determine the qualitative and quantitative composition of the solution with sufficient accuracy. At the same time, a qualitative characteristic of a substance is the magnitude of the potential difference sufficient for its electrochemical decomposition (half-wave potential E S), and a quantitative characteristic is the magnitude of the increase in current strength due to its electrochemical decomposition in solution (wavelength H, or the difference in the values ​​of the limiting diffusion current and residual current). To quantify the concentration of a substance in a solution, the following methods are used: the calibration curve method, the standard method, the additive method. The conductometric method of analysis is based on the dependence of the electrical conductivity of the solution on the concentration of the electrolyte. It is used, as a rule, in the variant of conductometric titration, the equivalence point at which is determined by the inflection of the titration curve (the dependence of electrical conductivity on the amount of added titrant). Amperometric titration is a kind of potentiometric titration, only the indicator electrode is a polarographic device, i.e. applied microelectrode with superimposed voltage.

PHYSICAL METHODS OF ANALYSIS, based on measuring the effect caused by the interaction. with in-tion of radiation - a stream of quanta or particles. Radiation plays roughly the same role that a reagent plays in chemical methods of analysis. measured physical. the effect is a signal. As a result, several or many measurements of the magnitude of the signal and their statistic-stich. processing receive analyte. signal. It is related to the concentration or mass of the components being determined.

Based on the nature of the radiation used, physical methods of analysis can be divided into three groups: 1) methods that use the primary radiation absorbed by the sample; 2) using primary radiation scattered by the sample; 3) using secondary radiation emitted by the sample. For example, mass spectrometry belongs to the third group - the primary radiation here is the flow of electrons, light quanta, primary ions or other particles, and the secondary radiation is decomposed ions. masses and charges.

From a practical point of view applications more often use other classification of physical methods of analysis: 1) spectroscopic. analysis methods - atomic emission, atomic absorption, atomic fluorescence spectrometry, etc. (see, for example, Atomic absorption analysis, Atomic fluorescence analysis, Infrared spectroscopy, Ultraviolet spectroscopy), X-ray spectroscopy, including X-ray fluorescence method and X-ray spectral microanalysis, mass spectrometry, electron paramagnetic resonance and nuclear magnetic resonance, electron spectrometry; 2) nuclear-no-phys. and radiochem. methods - radioactive analysis (see. Activation analysis), nuclear gamma-resonance, or Mössbauer spectroscopy, isotope dilution method ", 3) other methods, for example. X-ray diffractometry (see. Diffraction methods), etc.

The advantages of physical methods: ease of sample preparation (in most cases) and qualitative analysis of samples, greater versatility compared to chemical. and fiz.-chem. methods (including the possibility of analyzing multicomponent mixtures), a wide dynamic. range (i.e., the ability to determine the main, impurity and trace components), often low detection limits both in concentration (up to 10 -8% without the use of concentration) and in mass (10 -10 -10 -20 g), which allows you to spend extremely small amounts of samples, and sometimes carry out non-destructive analysis. Many physical methods of analysis make it possible to perform both gross and local and layer-by-layer analysis from spaces. resolution down to the monatomic level. Physical methods of analysis are convenient for automation.

Using the achievements of physics in the analyt. chemistry leads to the creation of new methods of analysis. Yes, in con. 80s appeared inductively coupled plasma mass spectrometry, nuclear microprobe (method based on registration x-ray radiation, excited by bombarding the sample under study with a beam of accelerated ions, usually protons). The areas of application of physical methods for the analysis of natural objects and technologies are expanding. materials. A new impetus to their development will give the transition from the development of theoretical. foundations of individual methods to create general theory physical methods of analysis. The purpose of such studies is to identify physical. factors that provide all connections in the analysis process. Finding the exact relationship of analyte. signal with the content of the determined component opens the way to the creation of "absolute" methods of analysis that do not require comparison samples. The creation of a general theory will facilitate the comparison of physical methods of analysis with each other, the correct choice of method for solving specific analytes. tasks, optimization of analysis conditions.

Lit .: Danzer K., Tan E., Molkh D., Analytics. Systematic review, trans. from German, M., 1981; Ewing G., Instrumental Methods of Chemical Analysis, trans. from English, M., 1989; Ramendik G.I., Shishov V.V., "Journal of Analytical Chemistry", 1990, vol. 45, no. 2, p. 237-48; Zolotov Yu.A., Analytical chemistry: problems and achievements, M., 1992. G.I. Ramendik.