Aflatoxin is a potent biological toxin produced by fungi Aspergillus flavus and A. parasiticus. Current quantification methods for aflatoxins are mostly established on immunoaffinity columns which are both costly and labor intensive. Inspired by smectites’ high aflatoxin adsorption capacity and affinity, a novel aflatoxin quantification sensor based on smectite-polyacrylamide (PAM) nanocomposite was fabricated. First, a smectite-PAM nanocomposite film was synthesized on flat silicon substrates which assembled smectite particles from the clay suspension. A layer-by-layer assembly process was developed to achieve uniform morphology and thickness of the nanocomposite films. During the aflatoxin quantification process, positive correlations between the fluorescence intensity from the aflatoxin B1 (AFB1) adsorbed smectite-PAM nanocomposite films and the AFB1 concentration in the test solutions were obtained. The smectite-PAM nanocomposite film has shown similar AFB1 adsorption capabilities as the smectite. Second, the smectite-PAM nanocomposite film was optimized in order to achieve the aflatoxin quantification at ppb level (below 20ppb) in corn extraction solutions. The smectite was modified by Ba2+, which had demonstrated to be able to improve its aflatoxin adsorption capacity. PAM aqueous solutions with the mass concentration ranging from 0.8% to 0.001% were tested. The results showed that the nanocomposite synthesized from 0.005% concentration of PAM solution generated the best properties. After the optimization, the smectite-PAM nanocomposite films achieved the detection of aflatoxin B1, B2, G1 and G2 (AFB2, AFG1 and AFG2) in 10 ppb corn extraction solution. Aflatoxin quantifications in AFB1 and AFB2 mixture solution, AFB1 and AFB2 mixture solution and AFB1 and AFG1 mixture solution were conducted, and the recoveries of last test ranged from 90.52% to 110.11% at low aflatoxin concentration (below 20 ppb). Third, in order to shorten the quantification duration and simplify the detection process, a novel aflatoxin detection array based on smectite-PAM nanocomposite and an improved fluorometric quantification method were developed. Through a microfluidic chip, the reaction time was reduced to 10~20min. Two concentration levels (20~80ppb/5~15ppb) of aflatoxin B1 spiked corn extraction solutions were tested. In the fluorometric quantification step, a common lab-use 365 nm ultraviolet lamp replaced the spectrofluorometer which simplified and accelerated the process.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-05T18:41:37Z No. of bitstreams: 1 Dissertação_Humbervania Reis Gonçalves da Silva_2012.pdf: 1948968 bytes, checksum: 1e2bef735b027e934bccadc6da99dff4 (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-06T11:31:39Z (GMT) No. of bitstreams: 1 Dissertação_Humbervania Reis Gonçalves da Silva_2012.pdf: 1948968 bytes, checksum: 1e2bef735b027e934bccadc6da99dff4 (MD5) / Made available in DSpace on 2016-09-06T11:31:39Z (GMT). No. of bitstreams: 1 Dissertação_Humbervania Reis Gonçalves da Silva_2012.pdf: 1948968 bytes, checksum: 1e2bef735b027e934bccadc6da99dff4 (MD5) / CAPES / A monitoração da qualidade dos combustíveis é importante, não apenas em decorrência do desempenho dos veículos, mas também devido ao impacto ambiental das emissões de poluentes. Combustíveis adulterados resultam em aquecimento e aceleração do motor, além de aumentarem o consumo de combustível, a emissão de material particulado e de gases de exaustão. No Brasil, na década de 90 houve várias experiências de produção e uso de biodiesel a partir de diversas matérias-primas de origem vegetal ou animal, assim como de óleo residual. No entanto, apenas com a Portaria Nº 310 de 27/12/2001, a ANP estabeleceu as especificações para comercialização de óleo diesel e sua mistura com 2% de biodiesel e definiu obrigações dos agentes econômicos sobre o controle de qualidade do biocombustível. O trabalho visa simplificar os testes utilizados para caracterizar as misturas de biodiesel e diesel, de B00 (0%v/v de biodiesel no diesel) até B100 (100%v/v de biodiesel puro). Foi utilizada a técnica de espectrofluorimetria total 3D em combinação com Análise do Componente Principal (PCA) para identificar adulteração de bicombustível, pela mudança dos valores de concentrações de biodiesel em diesel. Os espectros de emissão fluorescente das amostras foram realizadas em um espectrofluorímetro, onde a emissão foi detectada de 230 a 800 nm em intervalos de 0,5 nm enquanto as moléculas presentes na amostra sofriam excitação em comprimentos de onda fixos na faixa de 200 a 775 nm. Outros espectros de emissão fluorescente das amostras foram obtidos excitando-se as amostras com LED de 365 nm e capturando-se a emissão na faixa de 385 a 1000 nm com incremento de 1 nm. Foram preparadas 76 amostras, todas foram analisadas através da Espectroscopia de Fluorescência Total associada à PCA e foi possível identificar adulterações de diesel em decorrência do excesso de biodiesel, ultrapassando os valores permitidos por lei. / Monitoring of fuel quality is important, not only because of the performance of vehicles, but due to the environmental impact of emissions of pollutants. Adulterated fuels result in heating and acceleration of the motor, besides increasing the fuel consumption, emissions and particulate matter exhaust gas . In Brazil, in the 90s there were several experiences of production and use of biodiesel from various raw materials of vegetable or animal origin, as well as residual oil. However, only with Ordinance No. 310, 27/12/2001, ANP established specifications for commercialization of diesel and its mixture with 2% biodiesel and defined obligations of economic agents about the quality control of the biofuel. The work aims to simplify the tests used to characterize mixtures of biodiesel and diesel, B00 (0% v / v biodiesel in C) to B100 (100% v / v of pure biodiesel). We used the technique of spectrofluorimetry full 3D in combination with PCA to identify adulteration of biofuel, by changing the values of concentrations of biodiesel in diesel. The fluorescence emission spectra of the samples were performed in a spectrofluorometer where the emission was detected at 230-800 nm in steps of 0.5 nm while the sample suffered excitation in wavelengths fixed at 200-775 nm. Other fluorescent emission spectra of the samples were obtained by exciting the sample with LED of 365 nm and capturing the emission in the range 385 to 1000 nm with an increment of 1 nm. Have been prepared 76 samples, all were analyzed by Fluorescence Spectroscopy Total associated with PCA and were able to identify adulteration of diesel fuel due to the excess biodiesel, exceeding the values allowed by law.