Study of the process of tetracycline absorption by soil and its transformation during acid desorption

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Introduction. Currently, control over the soil entry of antibiotics used in agriculture is becoming an urgent problem of environmental hygiene. Tetracycline can enter the soil with the excrement of domestic animals and affect biological objects, both microbiological and plant. The chemical form of tetracycline in the soil and the options for its transformation, in particular during sample preparation for analysis, are factors that determine the intensity of this effect and the reliability of analytical control. The lack of information about the transformation of the drug under chemical influence determined the relevance of the research. Materials and methods. The studies were performed using the Stayer chromatographic system with a Shodex IC YS-50 150/4.6 cation column and a Kromasil C18 HPLC column with amperometric and conductometric detection. The objects of research were model soil samples with different tetracycline contents. When conducting research, soddy-podzolic soil from the «Nemchinovka» experimental field (Moscow region) and GSO No. chernozem were used. Results. Solutions obtained after acid-methanol desorption of tetracycline from soil samples were studied using HPLC and IC (Ionochromatographic methods). As a result of desorption, complex forms of substances, including both natural organic substances of the soil and tetracycline components, were established to pass into the aqueous phase. These forms of substances are fixed with a Shodex IC YS-50 cation exchange column and are not fixed by HPLC with a Kromasil C18 column. The possibility of isolating a chromatographic signal corresponding to the tetracycline component using ion chromatography has been demonstrated. Limitations. To create a method for measuring tetracycline in soil, it is necessary to test a larger number of soil species that differ in the content of organic matter to identify in detail the interfering effect of the organic matrix during chromatographic analysis. Conclusion. Research has shown tetracycline chemically to bind to soil matter, forming cationic complexes. After treating the soil with a mixture of concentrated hydrochloric acid and methanol, tetracycline is quantitatively extracted from the soil in combination with natural soil organic matter. These forms of substances are detected by a Shodex IC YS-50 cationic column and are not detected by HPLC with a Kromasil C18 column. Selective analysis of the cationic form containing the tetracycline moiety is possible.