Desenvolvimento e avaliação de um protótipo de colorímetro por imagens digitais.

Abstract

This work aims to develop a prototype system for colorimetric determination of digital images, as well as evaluate its functionality to determine phosphorus and fluorine's concentration in natural waters. It is motivated by the necessity of portable tools, others than the use of the spectrometer, to optimize the analysis of time, transportation costs and storage of samples. Initially developed as a generic tool, the prototype was applied to artificial colourized solutions analysis, and, later it was evaluated to predict phosphorus and fluorine in natural waters. Therefore, it was first developed a computer software for acquisition and processing of digital images, applying the RGB colour model and two of its derivations. The software, developed in MATLAB®2009a (MathWorks) and organized to present an easy graphic interface, allows to capture and process color images of the sample, saving the data in an Excel file. However, before reaching the results of the evaluation, it was necessary to build up a camera to acquire the digital images to stow a web cam, a cuvette support and a light source, strategically combined and accommodated, creating an optical path and avoiding external light noises during the image acquisition. Applying the initial analysis with artificial colors, there were obtained results with values of correlation coefficients greater than 0.99 for the analysis of blue, red and green colors The proposed method was compared to the reference method (spectrophotometer) in order for validation. Due to the usability condition of both the software and the prototype, the proposed method showed results equivalent to the reference method for determining phosphorus. Considering the results, it can be stated that the use of a prototype for colorimetric determination by digital images was relevant, even as a scanning method, identifying problematic samples and forwarding them to be analyzed through reference methods.