Desenvolvimento de método espectrofotométrico de titulação em microescala: análise do teor de ácido cítrico em refrigerantes de limão

Abstract

Soft drinks are beverages produced from water, sugar and vegetable juice or extract, where there is saturation of carbon dioxide. In 2018, a research was published, in which the risk of premature death and the development of some diseases are related to the consumption of drinks with added sugar. In the same year, the consumption of soft drinks increased globally, and the Brazilian production was 12,297,846 thousand liters. There is a wide variety of flavors on the market and each one has a certain specification. Anvisa regulates the content of sweeteners, colorants, preservatives and acidulants in soft drinks. Acidulants are substances that give acidic taste or increase the acidity of food and have several functions, among them viscosity modification, conservation in microbiological control and buffering action by pH control. Several techniques can be used to quantify these compounds, the official method being acid-base volumetry, which, however, is susceptible to analyst errors when establishing the equivalence volume. In this sense, this work aimed to develop an instrumental method of titration in micro scale using a low cost spectrophotometer. For this purpose a sample quantity is inserted in the cuvette together with the indicator and titrant is added until the color change indicated by the instrument is observed. After fixing the volumes of sample (1 mL) and phenolphthalein indicator (10 μL), the analysis of 5 soft drink samples was performed and the results were compared with those obtained by the official method. The values were statistically concordant, demonstrating the effectiveness of the proposed method. Thus, a low cost method was obtained, with minimal consumption of sample and reagents that produces results equivalent to those obtained by acid-base volumetry.