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Предложен твердотельный ИСЭ для определения гидрохлорида доксициклина. Особенностью конструкции является наличие трансдюсера в виде пластифицированной мембраны, содержащей полианалин. Трансдюсер находится между токоотводом и ионоселективной мембраной. Определены основные метрологические характеристики электрода. Установлено, что применение трансдюсера повышает стабильность потенциала электрода при измерениях. Показана возможность практического использования ИСЭ для количественного определения доксициклина гидрохлорида в лекарственных формах.

Окислением сополимеров N-винилпирролидона и 2-метил-5-винилпиридина надуксусной кислотой получены N-оксиды сополимеров с различной степенью N-оксидирования. Методом УФ-спектрофотометрии исследована кинетика N-оксидирования, рассчитаны константы скорости и определена зависимость предельной степени N-оксидирования от температуры процесса. Молекулярные характеристики N-оксидированных сополимеров установлены методом 13С ЯМР. Для практического контроля полноты протекания реакции предложен подход на основе прямой УФ-спектрофотометрии.

A series of N-oxides of N-vinylpyrrolidone and 2-methyl-5-vinylpyridine copolymers with various degrees of oxidation were prepared via oxidation of the copolymers by peracetic acid. The N-oxidation kinetic rate constants were calculated using UV spectrophotometry. The temperature dependence of the limiting N-oxidation was determined. The molecular-weight characteristics of the N-oxidized copolymers were established using 13 C NMR methods. An approach based on direct UV spectrophotometry was proposed for practical monitoring of the reaction completion (degree of conversion).Polymers and copolymers of N-vinylpyrrolidone (I) are broadly applied in pharmacy and medicine [1 -3] as a result of the discovery of their physiological activity [4]. Modern preparations based on them are known, e.g., Gemodez preparation for disinfection, anti-fainting, and blood-replacement and Sovigripp inactivated vaccine for flu prevention.Copolymers of I with vinylpyridine and its derivatives, in particular, 2-methyl-5-vinylpyridine (II), are promising [5,6]. A method for synthesizing copolymers of I and II was developed [6,7]. It was also shown that they had high immunomodulating activity that increased with increasing number of pyridine moieties in the macromolecules [4]. However, the last trend was associated with decreasing water-solubility [8], which was a serious deficiency of copolymers of I and II.The water-solubility of polymers containing pyridine moieties can be improved by N-oxidation [9]. Compounds with N-oxidized pyridine are known to possess biological, anticancer, and bactericidal activity [10]. In particular, polyvinylpyridine-N-oxide was demonstrated to be effective for treating lung diseases [11].The present work is focused on the synthesis of N-oxidized derivatives of copolymers of I and II in order to improve their solubility. The obtained N-oxidized copolymers could possibly exhibit pronounced biological activity comparable with that of the starting copolymers. EXPERIMENTAL PARTCopolymers of I and II that were synthesized at the Department of Biomedical and Pharmaceutical Technologies, Lomonosov MITKhT, and were characterized with viscosity-average molecular weight 29 kDa and I:II mole ratio 20:80 were studied. The copolymers were synthesized and their molecular weights were determined by the published methods [5,7].