Diffusion ordered NMR (DOSY) was applied to the determination of the average molecular weights of polymers based on the dependence of the measured self diffusion coefficient D on the correspond ing weights of a number of polymers of the same type. As a rule, a calibration function is plotted by varying DOSY experimental parameters for each particular test sample; however, this approach is inapplicable to the development of a standard procedure for the quantitative assessment of the molecular weights of dextrans. In this article, an optimization method is considered to ensure high resolution in terms of the values of D for dex trans without varying experimental conditions; this method makes it possible to evaluate the average molec ular weights of dextrans with a high accuracy over a wide range of their values.

The possibility of the application of diffusion ordered NMR spectroscopy to the study of the molecular weight distribution of hydroxyethyl starch is investigated. The use of regression equations relating these parameters to the coefficients of the self diffusion of polymer macromolecules as a whole, namely, the average coefficient of self diffusion D s and the coefficient of self diffusion at the peak maximum D p , is pro posed for the quantitative assessment of weight average (M w ) and number averaged (M n ) molecular weights and molecular weight at the peak maximum (M p ). It is shown that the determination of M w , M n , M p based on the data on D s gives the best results. It was found that the values of polydispersity indexes found using diffu sion ordered NMR spectroscopy are independent of the choice of diffusion parameter D s or D p .Keywords: diffusion ordered NMR spectroscopy, parameters of the molecular weight distribution of poly mers, average coefficient of self diffusion, self diffusion coefficient at the peak maximum, hydroxyethyl starch

Оценена специфичность различных вариантов методики подтверждения подлинности фармацевтической субстанции «бусерелина ацетат» методом ЯМР спектроскопии путем сравнительного анализа спектров 1H и 13C бусерелина ацетата и [5-D-тирозин]бусерелина ацетата в различных растворителях. Найдено, что максимальное различие в спектральных данных диастереомеров наблюдается при использовании дейтерированной воды в качестве растворителя. Показано влияние растворителя и внутримолекулярных невалентных взаимодействий на обменные прототропные превращения в L-гистидиновом фрагменте анализируемых олигомеров. От скорости прототропной таутомерии зависит ширина сигналов данной аминокислоты в спектрах 13C. Рекомендовано использовать в фармакопейном анализе вариант методики, основанный на 13C ЯМР спектроскопии (растворитель — D2O).

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