All existing methods of analytical chemistry can be divided into methods of sampling, sample decomposition, 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 quantity, 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 component being determined. This may be 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, color, line in the spectrum, etc. The appearance of an analytical signal must be reliably recorded. At a certain amount of a component, the magnitude of the analytical signal is measured: sediment mass, current strength, intensity of spectrum lines, etc. Then the content of the component is calculated using the functional relationship analytical signal - content: y=f(c), which is established by calculation or experiment and can be presented in the form of a formula, table or graph.
In analytical chemistry, a distinction is made between chemical, physical and physicochemical methods of analysis.
In chemical methods of analysis, the element or ion being determined is converted into some compound that has one or another characteristic properties, 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 obtain analyzes in a timely manner, while it is still possible to regulate the technological process. Therefore, along with chemical ones, physical and physicochemical methods of analysis are becoming increasingly widespread.
Physical methods analysis are based on the measurement of some
a system parameter that is a function of composition, for example, emission absorption spectra, electrical or thermal conductivity, potential of the electrode immersed in a solution, dielectric constant, refractive index, nuclear magnetic resonance, etc.
Physical methods of analysis make it possible to solve questions that cannot be resolved by methods of chemical analysis.
For the analysis of substances, physicochemical methods of analysis are widely used, based on chemical reactions, the occurrence of which is accompanied by a change physical properties the analyzed system, for example, its color, color intensity, transparency, thermal and electrical conductivity values, etc.
Physico-chemical methods of analysis They are distinguished by high sensitivity and speed of execution, make it possible to automate chemical analytical determinations and are indispensable when analyzing small quantities of substances.
It should be noted that it is not always possible to draw a strict line between physical and physicochemical methods of analysis. Sometimes they are combined under the general name “instrumental” methods, because To perform certain measurements, instruments are required that allow one to accurately measure the values of certain parameters that characterize certain properties of a substance.
PHYSICAL METHODS OF ANALYSIS
are based on measuring the effect caused by the interaction. with the substance of radiation - a flow of quanta or particles. Radiation plays approximately the same role as the reagent plays in chemical methods of analysis. Measured physical the effect is a signal. As a result, several or more measurements of signal magnitude and their statistics. processing the analyte is obtained. signal. It is related to the concentration or mass of the components being determined.
Based on the nature of the radiation used, F. m.a. can be divided into three groups: 1) methods using primary radiation absorbed by the sample; 2) using primary radiation scattered by the sample; 3) using secondary radiation emitted by the sample. Eg, 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 a misc. masses and charges.
From a practical point of view. applications, other classifications of f.m.a. are more often used: 1) spectroscopic. analysis methods - atomic emission, atomic absorption, atomic fluorescence spectrometry, etc. (see, for example, Atomic absorption analysis, Atomic fluorescence analysis, Infrared, Ultraviolet spectroscopy), including X-ray fluorescence method and X-ray spectral microanalysis, mass spectrometry, electronic paramagnetic resonance
And nuclear magnetic resonance, electron spectrometry; 2) nuclear-no-physics. and radiochem. methods - (see Activation analysis), nuclear gamma resonance, or Mössbauer spectroscopy, isotope dilution method", 3) other methods, e.g. X-ray diffractometry (see Diffraction methods),
and etc.
Advantages of physical methods: simplicity of sample preparation (in most cases) and qualitative analysis of samples, greater versatility compared to chemical methods. and physical-chemical methods (including the ability to analyze multicomponent mixtures), wide dynamic. range (i.e. the ability to determine major, 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 use extremely small amounts of samples, and sometimes carry out . Many F. m.a. allow you to perform both gross and local and layer-by-layer analysis of spaces. resolution down to the monatomic level. F.m.a. convenient for automation. Use of physics achievements in analytes. chemistry leads to the creation of new methods of analysis. So, in the end. 80s Inductively coupled plasma mass spectrometry and nuclear microprobe (a method based on recording X-ray radiation excited by bombarding the sample under study with a beam of accelerated ions, usually protons) appeared. The areas of application of f.m.a. are expanding. natural objects and technical materials. A new impetus for their development will be given by the transition from the development of theoretical. foundations of individual methods for creating general theory
F.m.a. The purpose of such studies is to identify physical. factors that provide all connections in the analysis process. Finding the exact relationship between analytes. signal containing the component being determined 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 F. m.a. among themselves, the correct choice of method for solving specific analytes. tasks, optimization of analysis conditions. Danzer K., Tan E., Molch 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, v. 45, no. 2, p. 237-48; Zolotev Yu. A., Analytical chemistry: problems and achievements, M., 1992. G. I. Ramendik.
Chemical encyclopedia. - M.: Soviet Encyclopedia. Ed. I. L. Knunyants. 1988 .
See what “PHYSICAL METHODS OF ANALYSIS” is in other dictionaries:
- (a. physical methods of analysis; n. physikalische Analyseverfahren; f. procedes physiques de l analysis; i. metodos fisicos de analisis) a set of methods of qualities. and quantities. analysis of substances based on the measurement of physical... ... Geological encyclopedia
physical methods of analysis- fizikiniai analizės metodai statusas T sritis chemija apibrėžtis Metodai, pagrįsti medžiagų fizikinių savybių matavimu. atitikmenys: engl. physical analytical methods; physical methods of analysis rus. physical methods of analysis... Chemijos terminų aiškinamasis žodynas
- (RMA), quality methods. and quantities. chem. analysis using radionuclides. The latter may be contained in the initial substance analyzed (for example, natural radionuclides of elements such as K, Th, U, etc.), maybe. introduced at a certain stage... ... Chemical encyclopedia
- (a. chemical methods of analysis; n. chemische Analyseverfahren; f. procedes chimiques de l analyse; i. metodos quimicos de analisis) a set of quality methods. and quantities. analysis of substances, basic on the use of chemicals reactions. … … Geological encyclopedia
Contents 1 Methods of electroanalytical chemistry 2 Introduction 3 Theoretical part ... Wikipedia
I. Method and worldview. II. Problems of historiography of pre-Marxist literary criticism. III. Short review the main trends of pre-Marxist literary criticism. 1. Philological study of word monuments. 2. Aesthetic dogmatism (Boileau, Gottsched... Literary encyclopedia
Mathematical methods used in precast concrete technology- – conditionally divided into three groups: group A – probabilistic statistical methods, including the use of general probability theory, descriptive statistics, sampling method and testing statistical hypotheses, variance and... ... Encyclopedia of terms, definitions and explanations of building materials
- (in analytical chemistry) the most important analytical operations necessary because most analytical methods are not selective enough (selective), i.e. the detection and quantification of one element (substance) is hampered by many... ... Wikipedia
TRIZ solution theory inventive problems, founded by Heinrich Saulovich Altshuller and his colleagues in 1946, and first published in 1956, is a technology of creativity based on the idea that “inventive creativity ... ... Wikipedia
Methods of chemical analysis physical- a set of physical methods of qualitative and quantitative analysis chemical compounds and elements. Based on measuring the physical properties of the substances under study (atomic, molecular, electrical, magnetic, optical, etc.). IN… … Dictionary in soil science
Books
- Physical methods of research and their practical application in chemical analysis. Textbook, Ya. N. G. Yaryshev, Yu. N. Medvedev, M. I. Tokarev, A. V. Burikhina, N. N. Kamkin. Tutorial intended for use in the study of disciplines: `Physical research methods`, `Standardization and certification of food products`, `Chemistry environment`, `Hygiene…
ANALYTICAL CHEMISTRY AND PHYSICAL-CHEMICAL METHODS OF ANALYSIS Publishing House TSTU Ministry of Education and Science Russian Federation State educational institution higher vocational education"Tambov State Technical University" M.I. LEBEDEV ANALYTICAL CHEMISTRY AND PHYSICAL-CHEMICAL METHODS OF ANALYSIS Lectures for the course Tambov Publishing House TSTU 2005 UDC 543 (075) BBK G4ya73-4 L33 Reviewers: Doctor of Chemical Sciences, Professor A.B. Kilimnik Candidate of Chemical Sciences, Associate Professor of the Department of Inorganic and physical chemistry TSU named after G.R. Derzhavina A.I. Ryaguzov Lebedeva, M.I. L33 Analytical chemistry and physical and chemical methods of analysis: textbook. allowance / M.I. Lebedeva. Tambov: Tamb publishing house. state tech. Univ., 2005. 216 p. The main issues of the course “Analytical chemistry and physico-chemical methods of analysis” are considered. After presenting the theoretical material, each chapter contains content blocks for testing knowledge using and the knowledge assessment rating is given. The third section of each chapter contains solutions to the most complex problems and their assessment in points. Intended for students of non-chemical specialties (200401, 200402, 240202, 240802, 240902) and compiled in accordance with standards and curricula. UDC 543 (075) BBK G4YA73-4 ISBN 5-8265-0372-6 © M. Lebedeva, 2005 © Tambov State Technical University (TSTU), 2005 Lebedeva Maria Ivanovna Analytical Chemistry and Physical and Chemical Methods of Analysis of the Lecture to course Editor V.N. Mitrofanova Computer prototyping D.A. Lopukhova Signed for publication on May 21, 2005 Format 60 × 84 / 16. Offset paper. Offset printing Times New Roman typeface. Volume: 12.55 conventional units. oven l.; 12.50 academic publication l. Circulation 200 copies. P. 571M Publishing and Printing Center of Tambov State technical university , 392000, Tambov, Sovetskaya, 106, room 14 PREFACE Without analysis there is no synthesis F. Engels Analytical chemistry is the science of methods for identifying chemical compounds, of the principles and methods of determining the chemical composition of substances and their structure. Analytical chemistry has acquired particular relevance nowadays, since the main factor of unfavorable anthropogenic impact, engineer, teacher, entrepreneur. A limited number of textbooks and teaching aids for the course “Analytical Chemistry and Physical-Chemical Methods of Analysis” for chemical students and their complete absence for the specialties “Standardization and Certification”, “Food Biotechnology”, “Environmental Protection Engineering”, as well as my many years of experience teaching this discipline at TSTU led to the need to compile and publish the proposed course of lectures. in the design of the work. 1 May be missing in some chapters 2 May be missing in some chapters “Analytical chemistry is sensitive to the demands of production and derives from this strength and impulses for further growth.” N.S. Kurnakov 1 ANALYTICAL CHEMISTRY AS A SCIENCE. BASIC CONCEPTS In solving major human problems (the problem of raw materials, food, nuclear energy, astronautics, semiconductor and laser technology), the leading place belongs to analytical chemistry. basis environmental monitoring is a set of various chemical sciences, each of which requires the results of chemical analysis, since chemical pollution is the main factor in the adverse anthropogenic impact on nature. The goal of analytical chemistry is to determine the concentration of pollutants in various natural objects. They are natural and waste waters of various compositions, bottom sediments analysis of substances and their application to solve national economic problems. Careful and constant monitoring of production and environmental facilities is based on the achievements of analytical chemistry. V. Ostwald wrote: “Analytical chemistry, or the art of recognizing substances or their constituent parts, occupies a special place among the applications of scientific chemistry, since the questions that it makes it possible to answer always arise when trying to reproduce chemical processes for scientific or technical purposes. Thanks to this significance, analytical chemistry has long been met with constant concern for itself...” 1.1 Short story development of analytical chemistry The history of the development of analytical chemistry is inseparable from the history of the development of chemistry and the chemical industry. Certain techniques and methods of chemical analysis have been known since ancient times (recognition of substances by color, smell, taste, hardness). In the 9th – 10th centuries. in Rus' they used the so-called “assay analysis” (determining the purity of gold, silver and ores). Thus, the records of Peter I about his “assay analysis” of ores have been preserved. Wherein qualitative analysis : “microcrystalscopic analysis.” The first classical works on chemical analysis belonged to academician V.M. Severgin, who published the “Guide to testing mineral waters.” In 1844, professor at Kazan University K.K. Klaus, analyzing “raw platinum”, discovered a new element – ruthenium. Technical analysis is divided into general - analysis of substances found in all enterprises (H2O, fuel, lubricants) and special - analysis of substances found only in a given enterprise (raw materials, intermediate products, production waste, final product). (determination of qualitative composition) always preceded quantitative analysis (determination of the quantitative ratio of components). performing analytical reactions indicating the conditions for their implementation. Its task is to master experimental skills and the essence of analytical reactions. Analytical chemistry methods are based on various principles. 1.3 CLASSIFICATION OF ANALYSIS METHODS 1 By objects of analysis: inorganic and organic.< 10 −6 г). 1.4 АНАЛИТИЧЕСКИЕ РЕАКЦИИ 1.4.1 Способы выполнения аналитических реакций В основе аналитических методов – получение и измерение аналитического сигнала, т.е. любое проявление химических и физических свойств вещества в результате протекания химической реакции. Аналитические реакции можно проводить «сухим» и «мокрым» путем. Примеры реакций, проводимых «сухим» путем: реакции окрашивания пламени (Na + – желтый; Sr 2+ – красный; Ba 2+ – зеленый; K + – фиолетовый; Tl 3+ – зеленый, In + – синий и др.); при сплавлении Na 2 B 4 O 7 и Co 2+ , Na 2 B 4 O 7 и Ni 2+ , Na 2 B 4 O 7 и Cr 3+ образуются «перлы» буры различной окраски. Чаще всего аналитические реакции проводят в растворах. Анализируемый объект (индивидуальное вещество или смесь веществ) может находиться в любом 2 By purpose: qualitative and quantitative. (solid, liquid, gaseous). The object to be analyzed is called a sample or sample. The same element in a sample can be in different chemical forms. For example: S 0 , S 2− , SO 2 − , SO 3 - etc. Depending on the purpose and objectives of the analysis, after transferring the sample into solution, elemental analysis (determining the total sulfur content) or phase analysis (determining the sulfur content in each phase or in its individual chemical forms) is carried out. 2 4 Reactions of formation of crystals of a strictly defined shape (microcrystalloscopic reactions). The need for separation and concentration may be due to the following factors: – the sample contains components that interfere with the determination;
Quantitative analysis makes it possible to establish quantitative relationships between the constituent parts of a given compound or mixture of substances. In contrast to qualitative analysis, quantitative analysis makes it possible to determine the content of individual components of the analyte or the total content of the analyte in the object under study. Methods of qualitative and quantitative analysis that make it possible to determine the content of individual elements in the analyzed substance are called elemental analysis; functional groups – functional analysis; individual chemical compounds characterized by a certain molecular weight - molecular analysis. A set of various chemical, physical and physicochemical methods for separating and determining individual structural (phase) components of heterogeneous systems that differ in properties and physical structure and limited from each other by interfaces is called phase analysis. 3 By method of implementation: chemical, physical and physico-chemical (instrumental) methods.
4 By sample weight: macro– (>> 0.10 g), semi-micro– (0.10 – 0.01 g), micro– (0.01 – 10 −6 g), ultramicroanalysis ( state of aggregation; development of analysis methods; analytical chemistry of individual objects. Depending on the purpose of the analysis, a distinction is made between qualitative analysis and quantitative analysis. The task of the first is to detect and identify the components of the analyzed sample, the second is to determine their concentrations or masses. Depending on which components need to be detected or determined, there are isotopic analysis, elemental analysis, structural group analysis (including functional analysis), molecular analysis, and phase analysis. Based on the nature of the analyzed object, the analysis of inorganic and organic substances is distinguished.
In theoretical In the fundamentals of analytical chemistry, metrology of chemical analysis, including statistical processing of results, occupies a significant place. The theory of analytical chemistry also includes the study of the selection and preparation of analytical samples. about drawing up an analysis scheme and choosing methods, principles and ways to automate analysis, the use of computers, as well as the fundamentals of national economies. use of chemical results. analysis. The peculiarity of analytical chemistry is the study of not general, but individual, specific properties and characteristics of objects, which ensures the selectivity of many. analytical methods. Thanks to close connections with the achievements of physics, mathematics, biology and so on. fields of technology (this especially concerns methods of analysis), analytical chemistry has been turned into a discipline at the intersection of sciences.
In analytical chemistry, there are methods of separation, determination (detection) and hybrid ones, combining methods of the first two groups. Determination methods are divided into chemical methods of analysis (gravimetric analysis, titrimetry), physical and chemical methods of analysis (for example, electrochemical, photometric, kinetic), physical methods of analysis (spectral, nuclear physical and others) and biological methods of analysis. Sometimes determination methods are divided into chemical, based on chemical reactions, physical, based on physical phenomena, and biological, using the response of organisms to changes in the environment.
Analytical chemistry defines the general approach to the selection of analytical pathways and methods. Methods for comparing methods, conditions for their interchangeability and combination, principles and ways to automate analysis are being developed. For practical purposes using the analysis, it is necessary to develop ideas about its result as an indicator of product quality, the doctrine of express control of technology. processes, creating cost-effective methods. Great importance for analysts working in various industries National economy, has unification and standardization of methods. A theory is being developed to optimize the amount of information required to solve an analytical problem.
Analysis methods. Depending on the mass or volume of the analyzed sample, separation and determination methods are sometimes divided into macro-, micro- and ultra-micro methods.
The separation of mixtures is usually resorted to in cases where the methods direct definition or detection does not allow a correct result to be obtained due to interfering influence of other components of the sample. Particularly important is the so-called relative concentration - the separation of small quantities of analyte components from significantly larger quantities of the main components of the sample. The separation of mixtures can be based on differences in the thermodynamic, or equilibrium, characteristics of the components (ion exchange constants, stability constants of complexes) or kinetic parameters. The separation methods used are mainly chromatography, extraction, precipitation, distillation, as well as electrochemical methods such as electrodeposition.
Physico-chemical methods of analysis, are based on the dependence of the physical properties of a substance on its nature, and the analytical signal is a value of a physical property, functionally related to the concentration or mass of the component being determined. Physicochemical methods of analysis may include chemical transformations of the compound being analyzed, sample dissolution, concentration of the analyzed component, masking of interfering substances, and others. Unlike “classical” chemical methods of analysis, where the analytical signal is the mass of a substance or its volume, physicochemical methods of analysis use radiation intensity, current strength, electrical conductivity, potential difference, etc. as an analytical signal.
Important practical significance have methods based on the study of emission and absorption electromagnetic radiation V various areas spectrum 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 of the electrical properties of a substance.
Chemical methods of analysis. Methods for determining the composition of substances based on their use chemical properties, are called chemical methods of analysis.
Chemical methods of analysis are widely used in practice. However, they have a number of disadvantages. Thus, to determine the composition of a given substance, it is sometimes necessary to first separate the component being determined from foreign impurities and isolate it in its pure form. Isolating substances in their pure form is often a very difficult and sometimes impossible task. In addition, to determine small amounts of impurities (less than ) contained in the analyzed substance, it is sometimes necessary to take large samples.
Physical methods of analysis. The presence of one or another chemical element can be detected in a sample without resorting to chemical reactions, based directly on the study of the physical properties of the substance under study, for example, the coloring of a colorless burner flame in characteristic colors by volatile compounds of certain chemical elements.
Methods of analysis that can be used to determine the composition of the test substance without resorting to the use of chemical reactions, are called physical methods of analysis. Physical methods of analysis include methods based on the study of optical, electrical, magnetic, thermal and other physical properties of the substances being analyzed.
The most widely used physical methods of analysis include the following.
Spectral qualitative analysis. Spectral analysis is based on the observation of emission spectra (emission or emission spectra) of the elements that make up the substance being analyzed (see below).
Luminescent (fluorescent) qualitative analysis. Luminescent analysis is based on the observation of luminescence (emission of light) of analytes caused by the action of ultraviolet rays. The method is used to analyze natural organic compounds, minerals, medications, a number of elements, etc.
To excite the glow, the substance under study or its solution is irradiated with ultraviolet rays. In this case, the atoms of the substance, having absorbed a certain amount of energy, go into an excited state. This state is characterized by a greater supply of energy than the normal state of matter. When a substance passes from excited to normal state Luminescence occurs due to excess energy.
Luminescence that decays very quickly after cessation of irradiation is called fluorescence.
By observing the nature of the luminescent glow and measuring the intensity or brightness of the luminescence of a compound or its solutions, one can judge the composition of the substance under study.
In some cases, determinations are made based on the study of fluorescence resulting from the interaction of the substance being determined with certain reagents. Luminescent indicators are also known, used to determine the reaction of the environment by changes in the fluorescence of the solution. Luminescent indicators are used in the study of colored media.
X-ray diffraction analysis. By using x-rays it is possible to establish the sizes of atoms (or ions) and their relative positions in the molecules of the sample under study, i.e., it turns out to be possible to determine the structure of the crystal lattice, the composition of the substance and sometimes the presence of impurities in it. The method does not require chemical treatment of the substance or large quantities.
Mass spectrometric analysis. The method is based on the determination of individual ionized particles rejected electromagnetic field to a greater or lesser extent depending on the ratio of their mass to charge (for more details, see book 2).
Physical methods of analysis, having a number of advantages over chemical ones, in some cases make it possible to solve problems that cannot be resolved by methods of chemical analysis; Using physical methods, it is possible to separate elements that are difficult to separate by chemical methods, as well as to continuously and automatically record readings.
Very often, physical methods of analysis are used along with chemical ones, which makes it possible to use the advantages of both methods. The combination of methods is especially important when determining minute amounts (traces) of impurities in analyzed objects.
