Análise rápida da acidez de bebidas em microplacas de papel empregando entalpimetria no infravermelho

Abstract

The paper devices are receiving high emphasis in chemical analysis due to the attractive features as low cost, facility of use and fabrication, low consumption of reagents and easy disposal, high surface area, portability and biodegradability. In this way, as an alternative for acidity evaluation in beverages, this work proposes an unprecedented combination of paper microplates and thermal infrared enthalpimetry (TIE), allowing a rapid and effective analytical method for determination of acidity in beverages according to the principles of green chemistry. Therefore, it was performed the determination of total acidity in soft drink samples and total, fixed and volatile in red, white and sparkling wine with comparison of results with conventional titration method. The proposed system was performed by the use of a microplates paper fabricated by the wax printing method, an infrared camera for temperature monitoring and a multichannel pipette for reagent addition. Firstly, it was observed that the conditions of pipette as well as the temperature measurement in data processing could directly influence the deviation of the results. Compared to conventional titration method the TIE in paper platform presented desirable results, with good agreement (from 96 to 104%) for all evaluated samples. Moreover, it was observed that it provided a higher sample throughput that reached 480 samples h-1 for fixed acidity. A significant reduction in the sample and reagent consumption was observed, with energy consumption up to 60 times lower in relation to conventional method. Thus, the proposed system in this work presented a good performance, and it could be considered a rapid, reliable and inexpensive to acidity analysis in routine following the principles of green chemistry.