Desenvolvimento de um espectrômetro de absorção molecular no visível utilizando smartphone e materiais de baixo custo: construção, validação e aplicação

Abstract

Spectrometry measures the wavelengths of radiation, allowing for analysis to determine how much radiation a chemical species has absorbed or emitted and, consequently, determine the concentration of its sample. Their use is extensive and, despite being efficient, they are relatively expensive and heavy, which poses limitations to their use. Thus, in this work, it was proposed the development of a spectrometry apparatus that would present itself as a simple and efficient analytical method. The construction of this device has been optimized, achieving the best results by adopting a rectangular cuvette holder with a brown interior. The ideal configuration was obtained with a distance of 0.0 cm between the smartphone camera and the sample cuvette and a distance of 30.0 cm between the cuvette holder and the card paper background, with no significant difference when using a distance of 20.0 cm. The ambient light was used as an illumination source, and the card paper background, with a complementary color to that of the sample, could be flat or curved. Validation of the device was carried out considering criteria of linearity, sensitivity, limit of detection and quantification, precision, and accuracy. For the validation step, a sensitivity of 0.0069 L.mg-1, a detection limit (DL) of 1.2 mg.L-1, and a quantification limit (QL) of 3.5 mg.L-1 were obtained for the device, while for the commercial equipment, the values obtained were a sensitivity of 0.0178 L.mg-1, a DL of 0.6 mg.L-1, and a QL of 1.9 mg.L-1.These parameters were compared with values obtained by already established and validated commercial equipment, having values within those established in the literature despite being lower than those obtained using commercial equipment. The proposed equipment was able to perform the measurements accurately when tested for analysis of two application scripts proposed for the device. As a result, it proved to be an excellent alternative to the commercial spectrometer in terms of cost, transportation, ease of use, and availability.