Abstract
In this work, the possibility of using reactions of electrogenerated titrants with phenolic compounds was studied and a method for their coulometric determination in medicaments by galvanostatic coulometry was developed. The research objects were: rutin, salicylic acid and drugs containing phenolic compounds such as «Ascorutin», «Salicylic Paste» and «Salicylic Ointment» of Russian manufacture. Electrogenerated halogens (Cl2, Br2 and I2) and hexacyanoferrate(III)-ions were used as titrants. It was found that for the quantitative determination of phenolic acids, the optimal reagent is electrogenerated bromine, for rutin - electrogenerated bromine and iodine, and for ascorbic acid - any of the studied electrogenerated titrants (Cl2, Br2, I2 and [Fe(CN)6]3-). The correct definition was checked by the «entered-found» method, the error does not exceed 2%. As experimental studies have shown, our method of coulometric titration with electrogenated bromine and iodine is characterized by good reproducibility of results, expression, accuracy and can be used to determine phenolic compounds in drugs, for example, «Ascorutin» tablets. It should be noted that by our procedure it is possible to determine the spectrum of phenol-containing compounds (rutin, ascorbic and salicylic acids) in drugs without their preliminary separation. Therefore, the coulometric method using electrogenerated titrants can be recommended for the determination of salicylic, ascorbic acids and rutin in dosage forms. The proposed method is accurate and eliminates the experiment error in comparison with the Pharmacopoeic method.
Highlights
The phenolic group is found in the structure of many medicinal substances and largely determines their pharmacological, physicochemical and chemical properties
We found that the electrogenated hexacyanoferrate(III)-ion and electrogenated iodine enter into redox reactions, but since the redox potential (0.356 V) is low, their oxidative force is not enough to oxidize salicylic acid
Salicylic acid is oxidized by chlorine, but this reaction proceeds nonstoichiometrically
Summary
The phenolic group is found in the structure of many medicinal substances and largely determines their pharmacological, physicochemical and chemical properties. Quality control of such medicinal substances requires the determination of indicators characterizing phenolic function. This makes it necessary to study the reactivity and methods of chemical analysis of drugs from the class of phenols. In order to establish the conformity of the quality of medicines to the regulated requirements, it is necessary to use various analytical methods. It is necessary to evaluate the suitability of analytical methods for their intended use. The State Pharmacopoeia [1] does not always offer the most reliable method for determining the active ingredient in the dosage form
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