Novas técnicas de introdução de amostras para espectrometria atômica: nebulização eletrônica e geração fotoquímica de vapores
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Data
2019-03-28
Autores
Gianeti, Thiago Marcelo Ribeiro
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A demanda por novos sistemas de nebulização e/ou introdução de amostras mais flexíveis e, preferencialmente, de baixo fluxo com aproveitamento total da solução em espectrometria atômica surge em decorrência da necessidade de desenvolvimento de novas interfaces para a hifenação com técnicas cromatográficas, a qual está sendo empregada em estudos de especiação química em que se tem pouca disponibilidade de amostras e necessidade de incremento da sensibilidade. Além disso, existe a possibilidade de criação de novas configurações de instrumentos portáteis, redução de custos e menor geração de descartes e efluentes. Neste contexto, foram estudados dois novos sistemas de introdução de amostras: nebulização eletrônica por malha oscilante e a geração fotoquímica de vapores. Nebulizadores de malha oscilante são dispositivos eletrônicos de geração de aerossol desenvolvidos para administração de fármacos específicos para doentes de fibrose cística dos pulmões. Trata-se de um dispositivo portátil, silencioso, sem a necessidade de gás para a geração do aerossol, produzindo um aerossol formado por gotículas de distribuição uniforme (monomodal) com tamanho de partículas de 3 µm. Não há relatos na literatura que, empregando estes sistemas em espectrometria atômica, haveria um grande potencial de abertura de um novo campo de estudos. Verificou-se que nebulizadores eletrônicos permitem que sejam promovidas determinações multielementares empregando apenas 100µL de solução da amostra com grande incremento de sensibilidade, podendo variar entre 10 até 200 vezes, dependendo do elemento e do comprimento de onda. Os melhores resultados foram obtidos para o elemento cadmio. Já a geração fotoquímica de vapores (PVG) é uma técnica para geração de compostos organometálicos voláteis dos elementos conhecidos como formadores de hidretos (As, Se, Sb, Bi, Pb, Sn, Te), mercúrio e alguns elementos de transição (por exemplo Co, Fe, Ni), os quais compõe um subconjunto de novas técnicas analíticas. Tais técnicas já são amplamente utilizadas no acoplamento à espectrometria atômica e espectrometria de massas, com o objetivo de melhorar a sensibilidade, eficiência de transporte e introdução do analito. A geração fotoquímica de espécies voláteis por radiação ultravioleta (UV-PVG) é, atualmente, a técnica mais promissora devido à sua simplicidade instrumental e possibilidade de utilização de fotocatalisador para a pré-redução de analitos formadores de hidretos, mercúrio e elementos de transição. Um fator crucial para o desenvolvimento da técnica de UV-PVG é construção do reator fotoquímico, uma vez que reatores de diferentes construções descritas na literatura produziram resultados contraditórios. Foi também objetivo deste trabalho projetar e construir novos tipos de reatores UV de fluxo altamente eficientes e aplicá-los para a determinação sensível de arsênio, um elemento ambientalmente e toxicologicamente importante. As figuras de mérito obtidas para o elemento As (III) foram LOD 2,9 µg L-1, LOQ 9,7 µg L-1 em um intervalo linear entre 25-1.000 µg L-1 com volume de injeção de 100 µL.
The need for new systems for nebulization and / or introduction of more flexible and preferably low flow samples with full use of the solution in atomic spectrometry arises through the need to develop new interfaces for the hyphenation with chromatographic techniques, which is being used in studies of chemical speciation in which there is little availability of samples and need for increased sensitivity. In addition, there is the possibility of creating new configurations of portable instruments, reducing costs and less generation of discards and effluents. In this context, two new systems of sample introduction were studied: electronic nebulization by vibrating mesh membrane and the photochemical generation of vapors. Vibrating mesh membrane nebulizers are electronic aerosol generation devices developed for administration of specific drugs to cystic fibrosis patients of the lungs. It is a portable, quiet device without the need for gas to generate the aerosol, producing an aerosol formed by uniformly distributed (monomodal) droplets with a particle size of 3 μm. There are no reports in the literature that, employing these systems in atomic spectrometry, there would be great potential for opening up a new field of study. It was verified that electronic nebulizers allow multielement determinations to be promoted employing only 100μL of sample solution with great increase of sensitivity, being able to vary between 10 until 200 times, depending on the element and wavelength. The best results were obtained for cadmium element. Photochemical vapor generation (PVG) is a technique for the generation of volatile organometallic compounds known as hydride formers (As, Se, Sb, Bi, Pb, Sn, Te), mercury and some transition elements Co, Fe, Ni), which compose a subset of new analytical techniques. Such techniques are already widely used in the coupling to atomic spectrometry and mass spectrometry, with the aim of improving the sensitivity, transport efficiency and introduction of the analyte. The photochemical generation of volatile species by ultraviolet radiation (UV-PVG) is currently the most promising method due to its instrumental simplicity and the possibility of using a photocatalyst for the pre-reduction of hydride forming analytes, mercury and transition elements. A crucial factor for the development of the UV-PVG technique is the construction of the photochemical reactor, since reactors of different constructions described in the literature have produced contradictory results. It was also the objective of this work to design and construct new types of highly efficient UV flow reactors and apply them for the sensitive determination of arsenic, an environmentally and toxicologically important element. The merit figures obtained for the element As (III) were LOD 2.9 μg L-1, LOQ 9.7 μg L-1 in a linear range between 25-1000 μg L-1 with an injection volume of 100 μL.
The need for new systems for nebulization and / or introduction of more flexible and preferably low flow samples with full use of the solution in atomic spectrometry arises through the need to develop new interfaces for the hyphenation with chromatographic techniques, which is being used in studies of chemical speciation in which there is little availability of samples and need for increased sensitivity. In addition, there is the possibility of creating new configurations of portable instruments, reducing costs and less generation of discards and effluents. In this context, two new systems of sample introduction were studied: electronic nebulization by vibrating mesh membrane and the photochemical generation of vapors. Vibrating mesh membrane nebulizers are electronic aerosol generation devices developed for administration of specific drugs to cystic fibrosis patients of the lungs. It is a portable, quiet device without the need for gas to generate the aerosol, producing an aerosol formed by uniformly distributed (monomodal) droplets with a particle size of 3 μm. There are no reports in the literature that, employing these systems in atomic spectrometry, there would be great potential for opening up a new field of study. It was verified that electronic nebulizers allow multielement determinations to be promoted employing only 100μL of sample solution with great increase of sensitivity, being able to vary between 10 until 200 times, depending on the element and wavelength. The best results were obtained for cadmium element. Photochemical vapor generation (PVG) is a technique for the generation of volatile organometallic compounds known as hydride formers (As, Se, Sb, Bi, Pb, Sn, Te), mercury and some transition elements Co, Fe, Ni), which compose a subset of new analytical techniques. Such techniques are already widely used in the coupling to atomic spectrometry and mass spectrometry, with the aim of improving the sensitivity, transport efficiency and introduction of the analyte. The photochemical generation of volatile species by ultraviolet radiation (UV-PVG) is currently the most promising method due to its instrumental simplicity and the possibility of using a photocatalyst for the pre-reduction of hydride forming analytes, mercury and transition elements. A crucial factor for the development of the UV-PVG technique is the construction of the photochemical reactor, since reactors of different constructions described in the literature have produced contradictory results. It was also the objective of this work to design and construct new types of highly efficient UV flow reactors and apply them for the sensitive determination of arsenic, an environmentally and toxicologically important element. The merit figures obtained for the element As (III) were LOD 2.9 μg L-1, LOQ 9.7 μg L-1 in a linear range between 25-1000 μg L-1 with an injection volume of 100 μL.
Descrição
Palavras-chave
Espectrometria atômica, Nebulizador de malha oscilante, PGV, Atomic spectrometry, Vibrating mesh membrane nebulizer, PVG