Avaliação de sensores ópticos para determinações de fluoreto em amostras de águas

Abstract

Digital imaging devices have the objective of reproducing this image formed by the human eye, which approaches the RGB system, an additive system in which the mixture of its colors results in white. This system is used in television and video devices and used to obtain digital images in analytical chemistry. Some information for chemical studies can be extracted from digital images and color solutions, with mathematical calculations for the determination of concentrations of species of interest in different samples. Portable photometric instruments consist of a radiation source, a monochromator, a cuvette with the solution and a detector. New studies include the LED as a radiation source and a detector with photodiodes in conjunction with the Arduino microcontroller for acquisition and conversion of analytical signals. In this work, a TCS 34725 color sensor and a TSL 2591 light sensor coupled to the Arduino Uno microcontroller were evaluated in order to be applied in chemical analysis for quantitative determinations. They were chosen because of their low cost, easy handling and quick responses. The color sensor provides the signals in RGB values, its operation is similar to a colorimeter, since the analysis by images and color occurs. It was evaluated if the fluoride concentration in the water is in the range indicated by the legislation, since the fluoride concentration must be in accordance with the stipulated for the prevention of dental caries in the population and its excess can cause fluorosis. The light sensor provides the values in amount of light, lux, this sensor approaches a photometer, which measure the light, where the chromophore must interact with the emitted light. Both sensors were compared to the UV-Vis spectrophotometer, calibration curves were plotted, indicating that the light sensor better approximates the spectrophotometer, after a correlation graph between them. Addition and recovery tests to evaluate the accuracy of the sensors were performed and the one that had the best performance was the TSL 2591 light sensor.