Desenvolvimento de sistemas analíticos portáteis espectrofotométrico e fluorimétrico baseados em imagem digital.

Abstract

In the present work, portable systems for analytical determinations based on digital image analysis were developed and applied. The first chapter presents general information about the use of color information, from digital images, to build the analytical signal. The second chapter presents the development of a portable spectrophotometric system that employs a 3D device to attach a webcam as a detection system; the system is fully powered by a computer's USB ports and makes use of an LED as a radiation source, powered by an adjustable voltage source. The preliminary performance of the system was evaluated in iron (II) and hypochlorite determinations, using color data from the RGB space and the effective absorbance mathematical processing. The system showed good analytical performance placing the LED on top of the cuvette and radiation source with maximum intensity. The third chapter presents the application of the spectrophotometric system developed in the determination of the external marker, titanium dioxide, in bovine feces. The method presented detection and quantification limits of 0.57 and 0.85 mg 100g-1, respectively; linear working range from 0.85 to 10 mg 100g-1 and accuracy, expressed in terms of RSD, of 1.86%. The accuracy of the method was verified by comparing the results found by the proposed method with the reference spectrophotometric method and there was no significant difference. The fourth chapter presents a portable fluorimetric system, which makes use of a monochromatic LED in the excitation stage, to determine quinine in commercial samples of tonic water. The system presented satisfactory performance, with a linear working range from 0.99 to 10 mg L-1, correlation coefficient equal to 0.998 and average precision (RSD) of 1.14%. The samples had quinine contents from 47.8 to 66.7 mg L-1, within the standards established by current legislation. The developed systems showed good performance, proving to be promising, alternatives to the reference methods, for analytical determinations based on digital image analysis