Análise de imagens para fins analíticos: aplicações ambientais e tecnológicas

• Autor(a) principal: Passaretti Filho, Juliano [UNESP]
• Data de Publicação: 2015
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/143007
• topic: Quimica atmosferica; Imagens digitais; Alimentos - Analise; Atmospheric chemistry

This work describes the development of sensitive, selective, and inexpensive methods with potential for use in environmental and technological applications. The techniques are based on reactions in aqueous solution that produce colored species that can be measured optically by means of the acquisition and processing of digital images. The experiments demonstrated the viability of using CMOS and CCD sensors to acquire digital images. In preliminary tests, comparison was made of analytical signals obtained using the digital image method and spectrophotometry, for measurements of nitrite, inorganic phosphate, and residual ozone in water. No statistically significant differences were observed between the two techniques, at a confidence level of 95%. The reliability of the results obtained using the new method then enabled new methods to be developed for environmental applications such as the determination of atmospheric SO2 and NO2. The determination of NO2 in air employed the Griess-Saltzman (GS) reaction, in which a rosecolored product is formed that absorbs at a wavelength of 540 nm. Air sampling was performed using C18 cartridges impregnated with triethanolamine (TEA), at a flow rate of 0.5 L min-1 for 60 min. The analyte was solubilized using an alcoholic solution of methanol/water, and then transferred to a 10.0 mL volumetric flask containing 4.0 mL of the GS reagent. A 4.0 mL aliquot was placed on an acrylic surface and digital images of the solution were acquired using a scanner. Processing of the images then resulted in analytical signals that were proportional to the NO2 concentration. The detection limit was 12 ppb, the relative error was 7.0 %, and the coefficient of variation was 3.2 %. In order to improve the detection limit, the solution volume was optimized (300 μL) and a new procedure for acquisition and treatment of the digital images was implemented, resulting in a reduction...