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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Chromatography. History and essence of scientific discovery
Directory / The most important scientific discoveries Many discoveries of the past century are due to the Russian scientist Mikhail Tsvet and his method of chromatographic analysis. A large number of outstanding researchers owe him their successes, and many Nobel Prizes! "...Without the work of Michael Tsveta, we, all the "pigmenters", would have nothing to do ..." - this is the opinion of one famous English scientist. Mikhail Semenovich Tsvet (1872–1919) - the son of an Italian woman and a Russian intellectual. He was born in Italy in the city of Asti, not far from Turin. In 1891, Mikhail graduated from the Geneva Gymnasium and entered the Faculty of Physics and Mathematics at the University of Geneva. In October 1896, after presenting his dissertation "Study of cell physiology. Materials for the knowledge of the movement of protoplasm, plasma membranes and chloroplasts", Tsvet received a diploma of a doctor of natural sciences. In December of the same year, he arrives in St. Petersburg. Mikhail did not know that a degree from the University of Geneva is not recognized in Russia. Therefore, he had to work for the famous botanist Andrey Sergeevich Famintsin, who also studied chlorophyll, one might say, on a bird's right. In St. Petersburg, Tsvet met other outstanding botanists and plant physiologists: I.P. Borodin, M.S. Voronin, A.N. Beketov. It was a brilliant society of original, thoughtful thinkers and skilled experimenters. Tsvet continued his research on chloroplasts, while at the same time preparing for new master's examinations and for the defense of his dissertation. He passed the exams in 1899, and he defended his master's thesis at Kazan University on September 23, 1901. Since November 1901, Tsvet has been working as an assistant at the Department of Plant Anatomy and Physiology at the University of Warsaw. At the XI Congress of Naturalists and Physicians, Mikhail Semenovich made a report "Methods and tasks of the physiological study of chlorophyll", in which he first reported on the method of adsorption chromatography. Mikhail Semenovich solved the problem of separating green leaf pigments for a long time, and they are very similar in properties. In addition, the leaves contain other, very bright, pigments - carotenoids. It is thanks to carotenoids that yellow, orange, purple leaves appear in autumn. However, until the chlorophylls were destroyed, it was almost impossible to separate them from the carotenoids. As Yu.G. Chirkov, “apparently, the discovery of Color was a reaction to the methods of their separation that were then crude and deadly for pigments. Here is one of the methods. First, an alcoholic extract of chlorophyll was extracted, then it was boiled for three hours with the addition of strong alkali (caustic potassium) to the solution. As a result, chlorophyll decomposes into its constituent parts - green and yellow pigments. But after all, in the process of making this potion (almost alchemical manipulations), natural chlorophyll could be destroyed. And then the researcher would have to deal with pieces of pigments, and even with the products of their chemical transformation. S.E. writes about how the great discovery happened. Shnol: "He took a glass tube, filled it with chalk powder and poured a little alcoholic extract of the leaves on the top layer. The extract was brown-green in color, and the top layer of the chalk column became the same color. And then M.S. began to pour drops from above into pure alcohol drop by drop another portion of the solvent eluted the pigments from the chalk grains, which moved down the tube, where the fresh chalk grains adsorbed the pigments and, in turn, gave them to new portions of the solvent. entrained by the mobile solvent, different pigments moved along the chalk column at different speeds and formed uniform colored bands of pure substances in the chalk column.It was beautiful.A bright green band, a band slightly yellower than green - these are two types of chlorophylls - and a bright yellow-orange band of carotenoids. MS called this picture a chromatogram." In 1903, Mikhail Semenovich Tsvet read a report "On a new category of adsorption phenomena and their application to biochemical analysis." Here, for the first time, he sets out in detail the principle of his method of adsorption analysis. “The color showed,” writes Chirkov, “that when plant pigments dissolved in a liquid are passed through a layer of a colorless porous sorbent, individual pigments are arranged in the form of colored zones - each pigment has its own color or at least a shade. Sorbent powder (it can be chalk, powdered sugar ...) adsorbs (superficially absorbs: Latin adsorbere means "swallow") different pigments with unequal strength: some can "slip" further with the current of the solution, others will be delayed closer. Color called the chromatogram, and the method - chromatography. Thus, a seemingly insurmountable problem was solved. The method turned out to be ingeniously simple. It is nothing like the cumbersome, reagent-intensive complex procedures used before. Perhaps this simplicity was the reason that most of his contemporaries either did not accept this amazing discovery, or, even sadder, sharply rebelled against its author. But time put everything in its place. Color invented chromatography for chlorophyll research. He first isolated a substance that he called chlorophyll alpha and chlorophyll beta. It turned out to be suitable for studying not only pigments, but also colorless, uncolored mixtures - proteins, carbohydrates. By the sixties of the twentieth century, several thousand studies had already been devoted to chromatography. Chromatography has become a universal method. "... The principle of chromatographic separation of substances, discovered by M. Tsvet, underlies many different methods of chromatographic analysis. Without its use, most of the achievements in science and technology of the XNUMXth century would not have been possible ... At the heart of all this is one general idea. She is simple. This is essentially the idea of a geometric progression. Let there be two substances very similar in all their properties. Neither precipitation, nor extraction, nor adsorption can separate them to a noticeable degree. Let one substance be adsorbed on the surface, for example, calcium carbonate (i.e., less than 1 percent). In other words, its content on the adsorbent will be 0,99 of the content of another. Let us treat the adsorbent with some solvent so that desorption (detachment) and elution (washing out) of both substances occur and both of them pass from the adsorbent to the solvent, and transfer this resulting solution to a fresh portion of the adsorbent. Then the proportion of the first substance on the surface of the adsorbent will again be equal to 0,99 of the content of the second, i.e., a part equal to 0,99 x 0,99 = 0,98 of the initial amount is adsorbed. Once again, we will carry out the elution and adsorption again - now the proportion of the first substance will be 0,98 x 0,99 \u0,97d 1 of the content of the second. In order for the content of the first substance on the next portion of the adsorbent to be only 200 percent of the content of the second, it will be necessary to repeat the adsorption-elution cycle about XNUMX times... The idea of multiple re-adsorption to separate substances can be modified into multiple redistribution of a mixture of substances in a system of immiscible solvents. This is the basis of partition chromatography. The same idea underlies modern electrophoresis methods, when a mixture of substances moves at different speeds over various adsorbents in an electric field. The same principle is used in the separation of isotopes by diffusion through many porous partitions." The principle of chromatographic distribution of substances, discovered by Color, is used in various fields of human activity. In particular, it is used for the isolation and purification of antibiotics in medicine and for the separation of isotopes in the production of nuclear fuel. Author: Samin D.K.
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