Determinação colorimétrica de glicose em soluções de reidratação utilizando imagens digitais

Abstract

Carbohydrates are very important biomolecules for life. As well as being the main source of energy production in non-photosynthetic cells, they also have structural and energy storage functions. Oral rehydration solutions are used to prevent dehydration by replenishing water and electrolytes lost after vomiting or acute diarrhea. These solutions contain glucose as the main ingredient. In this work, a colorimetric method for determining glucose was developed using a portable device that has an endoscopic camera for capturing digital images. The images were processed using the PhotoMetrix application. The colorimetric analysis consisted of the loss of the blue color of the Benedict's reagent, which contains copper (II) ions, when reacting with reducing sugars. To define the optimum experimental conditions for the focal length of the endoscopy camera (2 to 20 mm) and the light intensity applied by a light-emitting diode (30 to 180 lx), a Doehlert-type design of experiments was used, with a quadratic model for two variables. Multivariate calibration using the partial least squares (PLS) method and univariate calibration using individual channels and the resulting RGB vector were explored. Sample preparation consisted of solubilization, clarification and dilution. The method's optimization conditions were a focal length of 9.68 mm and 30 lx of light intensity. The regression method that showed the lowest value for the root mean square error of prediction (RMSEP) and the best correlation coefficient was using the RGB vector in the univariate calibration mode, with 0.20 g L-1 and 0.996, respectively. The determination of glucose in two samples, a ready-to-drink solution and a powder for preparation, resulted in concentrations of 17.0 ± 0.6 and 23.3 ± 1.8 g L-1 respectively. The accuracy of the method was verified by comparing the results obtained by the proposed method with the Lane-Eynon titration reference method. No significant differences were observed between the results obtained by the proposed and the reference method. The limit of quantification was 0.17 g L-1. The method developed has advantages such as low reagent consumption compared to the reference method, as well as low cost, ease of operation and fast data processing.