Influência na escolha de indicadores ácido-base na determinação de ácido acetilsalicílico em comprimidos utilizando a volumetria de neutralização

Abstract

The aim of the present study was to observe the influence in the choice of acid-base indicators in the determination of acetylsalicylic acid in tablets using the neutralization volumetry. The tests were performed with five different indicators, phenolphthalein, thymol blue, bromothymol blue, phenol red and thymolphthalein. Tablets containing acetylsalicylic acid (ASA) were purchased from the local Natal market and the samples were weighed, crushed and stored. Initially the samples were characterized by the techniques of Thermogravimetry (TG), Differential Exploration Calorimetry (DSC) and absorption spectroscopy in the infrared region.Subsequent to the AAS titrations with the five indicators, the concentration of the active principle was calculated according to the values obtained by the neutralization volumetry. The results showed that the acid-base indicators selected showed concentrations of 53,11%, 53,11%, 54,16%, 53,58% e 60,07% for phenolphthalein, thymol blue, bromothymol blue, Red phenol and thymolphthalein respectively. It was observed that four of the AAS concentration values are very close to the value established by the Brazilian Pharmacopoeia, thus indicating that the indicators can be used in this determination. Thus, the results of neutralization volumetry with different acid-base indicators were shown to be effective and consistent in the determination of acetylsalicylic acid.