Sensor de cores RGB para determinações colorimétricas: avaliação e análise quantitativa de soluções coloridas

Abstract

In this work a RGB sensor has been evaluated for quantitative analysis of colored solutions. The response ability of the sensor to different colored solutions was carefully evaluated for a better understanding of which spectral bands are filtered and processed by each sensor channel. The effective RGB sensor capacity, which is the sensor´s capability to illuminate and detect electromagnetic radiation reflected by samples, was observed in the range of 415-564; 440-600 and 510-750 nm for blue, green and red channels, respectively. These results can contribute to the understanding of the interaction between the light emitted by the built-in LED and the signals obtained by the RGB channels for different quantitative determinations. Aiming to investigate the interaction between the RGB sensor and colored substances and thereafter achieve quantitative optical analysis, different colored dyes were chosen for the RGB sensor capability evaluating, covering a range of colors. The analytical performance of RGB sensor yielded a linear range of 5.0 − 50.0 µmol L-1 for indigo blue dyes solutions and 5.0 – 25.0 µmol L-1 for the other dyes. The work ability of this sensor was demonstrated by colorimetric method for determinations of iron in soil and childish supplement samples by thiocyanate reaction. The use of RGB sensor for colorimetric determination presented an analytical performance similar to those obtained with a commercial spectrophotometer, and it is not necessary to use computers for image processing to acquire RGB values. The proposed device has a low cost, around US$35,00, considering the use of Arduino controller board, the value of RGB sensor and the cuvette holder 3D printing, this value is lower than that of entry-level smartphones currently available on the market. In addition, this sensor also contributes to meeting the requirements of generating an Internet of Analytical Things (IoAT) for quantitative analysis of color solutions.