Desenvolvimento da técnica DGT com membrana ligante de quitosana natural e membrana difusiva de agarose
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2022-12-22
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Universidade Estadual Paulista (Unesp)
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Frente à evolução da industrialização, aliada com o crescimento intenso da agricultura e dos principais centros urbano-industriais, os corpos hídricos vêm sofrendo com a entrada de grandes quantidades de contaminantes e compostos químicos, como os metais potencialmente tóxicos. O monitoramento dos corpos hídricos é de grande importância, uma vez que são utilizados para abastecimento público e diversas outras atividades como irrigação e pesca, e a técnica de difusão em filmes finos por gradientes de concentração (DGT) tem se mostrado eficiente no auxílio ao monitoramento destes metais em meios aquosos. Técnica baseada na 1ª Lei de Difusão de Fick, convencionalmente utiliza a membrana ligante feita com resina Chelex-100 e a membrana difusiva de acrilamida-agarose. Entretanto, esta resina é artificial e seus resultados são limitados. Uma alternativa para esta questão seria utilizar materiais de origem natural para fabricação do gel ligante, como a quitosana, que se trata de um polímero natural, biodegradável e atóxico. Sendo assim, nesse trabalho o dispositivo DGT foi confeccionado com materiais alternativos, sendo eles: filme de quitosana natural como agente ligante e gel de agarose como gel difusivo para a determinação dos coeficientes de difusão e adsorção dos analitos Cd (II), Cu (II) e Zn (II) em ambientes aquáticos. Os dispositivos montados com os materiais alternativos foram validados a partir de curvas de imersão nos diferentes analitos analisados, onde foram obtidas retas que comprovam o cumprimento da Lei de Fick, ou seja, comprovam que podem ser utilizados para a técnica DGT. No teste de câmara de difusão, o gel de agarose apresentou coeficiente de difusão para os íons Cd (II), Cu (II) e Zn (II), respectivamente, de 5,09 x 10-6 cm2 s -1 ; 2,83 x 10-6 cm2 s -1 e 1,70 x 10-6 cm2 s -1 . Os mesmos coeficientes foram determinados utilizando diretamente os dispositivos DGT e os valores de coeficiente de difusão foram de 2,45 x 10-6 cm2 s -1 ; 3,56 x 10-6 cm2 s -1 e 1,27 x 10-6 cm2 s -1 , para Cd (II), Cu (II) e Zn (II), respectivamente. Os resultados dos coeficientes de difusão obtidos em ambos os testes foram mais semelhantes para Cu (II) e Zn (II) quando comparados a diferença entre ambos os coeficientes obtidos para o Cd (II), sendo assim concluiu-se que o dispositivo DGT com os materiais alternativos foi efetivo, mas deve ser feita uma otimização do processo para obter resultados mais eficientes.
Faced with the evolution of industrialization, combined with the intense growth of agriculture and the main urban-industrial centers, water bodies have been suffering from large amounts of contaminants and chemical compounds such as potentially toxic metals. The monitoring of water bodies is of great importance, since they are used for public supply and several other activities such as irrigation and fishing, and the thin film diffusion technique by concentration gradients (DGT) has been shown to be efficient in helping to monitor these metals in aqueous media. Technique based on Fick's 1st Law of Diffusion, conventionally uses the binding membrane made with Chelex-100 resin and the diffusive membrane of acrylamide-agarose. However, this resin is artificial and its results are limited. An alternative to this issue would be to use materials of natural origin to manufacture the binding gel, such as chitosan, which is a natural, biodegradable and non toxic polymer. Therefore, in this work, the DGT device was made with alternative materials, namely: natural chitosan film as a binding agent and agarose gel as a diffusive gel for the determination of diffusion and adsorption coefficients of Cd (II), Cu (II) and Zn (II) analytes in aquatic environments. The devices assembled with alternative materials were validated based on immersion curves in the different analyzed analytes, where straight lines were obtained that prove compliance with Fick's Law, that is, they prove that they can be used for the DGT technique. In the diffusion camara assay, the agarose gel presented a diffusion coefficient for Cd (II), Cu (II) and Zn (II) ions, respectively, of 5,09 x 10-6 cm2 s -1 ; 2,83 x 10-6 cm2 s -1 and 1,70 x 10-6 cm2 s -1 . The same diffusion coefficient were directly determined by DGT devices and the values of diffusion coefficient were 2,45 x 10-6 cm2 s -1 ; 3,56 x 10-6 cm2 s -1 and 1,27 x 10-6 cm2 s -1 , for Cd (II), Cu (II) and Zn (II), respectively. The results of the diffusion coefficients obtained in both tests were more similar for Cu (II) and Zn (II) when comparing the difference between both coefficients obtained for Cd (II), so the conclusion is that the DGT device with alternative materials was effective, but an optimization of the process should be done to obtain results that are more efficient.
Faced with the evolution of industrialization, combined with the intense growth of agriculture and the main urban-industrial centers, water bodies have been suffering from large amounts of contaminants and chemical compounds such as potentially toxic metals. The monitoring of water bodies is of great importance, since they are used for public supply and several other activities such as irrigation and fishing, and the thin film diffusion technique by concentration gradients (DGT) has been shown to be efficient in helping to monitor these metals in aqueous media. Technique based on Fick's 1st Law of Diffusion, conventionally uses the binding membrane made with Chelex-100 resin and the diffusive membrane of acrylamide-agarose. However, this resin is artificial and its results are limited. An alternative to this issue would be to use materials of natural origin to manufacture the binding gel, such as chitosan, which is a natural, biodegradable and non toxic polymer. Therefore, in this work, the DGT device was made with alternative materials, namely: natural chitosan film as a binding agent and agarose gel as a diffusive gel for the determination of diffusion and adsorption coefficients of Cd (II), Cu (II) and Zn (II) analytes in aquatic environments. The devices assembled with alternative materials were validated based on immersion curves in the different analyzed analytes, where straight lines were obtained that prove compliance with Fick's Law, that is, they prove that they can be used for the DGT technique. In the diffusion camara assay, the agarose gel presented a diffusion coefficient for Cd (II), Cu (II) and Zn (II) ions, respectively, of 5,09 x 10-6 cm2 s -1 ; 2,83 x 10-6 cm2 s -1 and 1,70 x 10-6 cm2 s -1 . The same diffusion coefficient were directly determined by DGT devices and the values of diffusion coefficient were 2,45 x 10-6 cm2 s -1 ; 3,56 x 10-6 cm2 s -1 and 1,27 x 10-6 cm2 s -1 , for Cd (II), Cu (II) and Zn (II), respectively. The results of the diffusion coefficients obtained in both tests were more similar for Cu (II) and Zn (II) when comparing the difference between both coefficients obtained for Cd (II), so the conclusion is that the DGT device with alternative materials was effective, but an optimization of the process should be done to obtain results that are more efficient.
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Monitoramento Ambiental, Metais Toxicologia, Contaminação, Quitosana