Estudo do coeficiente de distribuição do Cr em águas naturaisDistribution coefficient study of Cr in natural waters

A distribuição de um metal pesado entre a fase dissolvida e o material particulado em suspensão (MPS) é um dos mais importantes mecanismos no controle do transporte desse poluente em ambientes aquáticos. Quanto maior o valor de Kd (coeficiente de distribuição) maior a tendência do metal estar complexado ao material particulado. O objetivo deste trabalho foi realizar um estudo do mecanismo de distribuição de Cr nas formas dissolvidas (D) e no material particulado em suspensão (MPS) em águas naturais. As amostras de águas naturais foram coletadas em diferentes pontos ao longo de um córrego pertencente à região de Guarapuava-PR. O procedimento analítico utilizado para a determinação do Cr no MPS foi realizado através da filtração das amostras em membrana 0,45μm, digestão da membrana contendo o MPS seguido de mineralização ácida. Para a determinação do Cr na forma dissolvida utilizou-se a água obtida através da filtração, seguida de acidificação e redução do volume por evaporação. Todas as medidas foram realizadas em um espectrômetro de absorção atômica em chama. O altos valores de Kd obtidos comprovaram uma maior afinidade do Cr pelo MPS devido a provável formação de complexos estáveis entre o Cr e ligantes naturais.Abstract Heavy metal distribution between the dissolved phase and suspended particulate matter (SPM) is one of the most important mechanisms for the pollutant transport control in aquatic environments. How much bigger the Kd value, the bigger is the metal trend to be complexed to the particulate material. The objective of this work was to carry through a study of Cr distribution mechanism in the dissolved forms (D) and the suspended particulate matter (SPM) in natural waters. The natural water samples had been collected in different points throughout of a stream pertaining to the Guarapuava-PR region. The used analytical procedure for the Cr determination in the SPM was carried through the samples filtration in 0,45μm membrane, digestion of the membrane containing the SPM, followed of acid mineralization. For the Cr determination in dissolved form it was used water gotten through the filtration, followed of acidification and volume reduction by evaporation. All the measures had been carried through in one atomic absorption spectrophotometer by flame. The high gotten values of Kd had proven a bigger Cr affinity for the MPS due to the probable formation of steady complexes between the Cr and natural ligands

Comparative in vitro toxicity of a graphene oxide-silver nanocomposite and the pristine counterparts toward macrophages

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Graphene oxide (GO) is a highly oxidized graphene form with oxygen functional groups on its surface. GO is an excellent platform to support and stabilize silver nanoparticles (AgNP), which gives rise to the graphene oxide-silver nanoparticle (GOAg) nanocomposite. Understanding how this nanocomposite interacts with cells is a toxicological challenge of great importance for future biomedical applications, and macrophage cells can provide information concerning the biocompatibility of these nanomaterials. The cytotoxicity of the GOAg nanocomposite, pristine GO, and pristine AgNP was compared toward two representative murine macrophages: a tumoral lineage (J774) and peritoneal macrophages collected from Balb/c mouse. The production of reactive oxygen species (ROS) by J774 macrophages was also monitored. We investigated the internalization of nanomaterials by transmission electron microscopy (TEM). The quantification of internalized silver was carried out by inductively coupled plasma mass spectrometry (ICP-MS). Nanomaterial stability in the cell media was investigated overtime by visual observation, inductively coupled plasma optical emission spectrometry (ICP OES), and dynamic light scattering (DLS). Results: The GOAg nanocomposite was more toxic than pristine GO and pristine AgNP for both macrophages, and it significantly induced more ROS production compared to pristine AgNP. TEM analysis showed that GOAg was internalized by tumoral J774 macrophages. However, macrophages internalized approximately 60 % less GOAg than did pristine AgNP. The images also showed the degradation of nanocomposite inside cells. Conclusions: Although the GOAg nanocomposite was less internalized by the macrophage cells, it was more toxic than the pristine counterparts and induced remarkable oxidative stress. Our findings strongly reveal a synergistic toxicity effect of the GOAg nanocomposite. The toxicity and fate of nanocomposites in cells are some of the major concerns in the development of novel biocompatible materials and must be carefully evaluated.Graphene oxide (GO) is a highly oxidized graphene form with oxygen functional groups on its surface. GO is an excellent platform to support and stabilize silver nanoparticles (AgNP), which gives rise to the graphene oxide-silver nanoparticle (GOAg) nanoco14CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)140560/2014-9The authors thank the National Council for Technological and Scientific Development (CNPq) for the PhD student scholarship (140560/2014-9) and the financial support. The authors also acknowledge Dr. Daniel Ruiz Abanádes for suggestions, Renata Magueta fo

Evaluation and correction of interferences on the determination of As and Se by inductively coupled plasma techniques

The aim of the thesis was to evaluate different strategies for correcting spectral and non-spectral interferences on As and Se determination by inductively coupled plasma optical emission spectrometry (ICP OES) and mass spectrometry (ICP-MS) techniques. The determination of 75As+ and 80Se+ isotopes by ICP-MS is strongly affected by the presence of 40Ar35Cl+ and 40Ar2 +, respectively. These interferences can be solved using strategies of sample preparation, cool plasma and more recently collisions and reactions cells. It was studied here a new device for correcting those spectral interferences by the introduction of H2 and He gases through the sampler and skimmer cones present in the collision reaction interface (CRI). The introduction of H2 gas through the skimmer cone was more efficient for destroying polyatomic ions. Lower limits of detection (LOD), 0.019 and 0.097 ng mL-1 for 75As+ and 80 Se+ isotopes, respectively, were obtained by adding 80 mL min-1 H2 through the skimmer cone. The accuracy was demonstrated using two certified reference materials oyster tissue and mussel tissue. Matrix effects may also be corrected using suitable calibration strategies, such as internal standard or the standard additions method. For determination of As and Se by ICP OES it was evaluated a new nebulizer named FB®MN to correct matrix effects and to reduce interferences applying on-line calibration strategies. The aerosol generated by FB®MN was characterized and compared with the aerosol generated by a conventional pneumatic nebulizer (Micromist®). Solutions containing 0.05 and 0.10 mol L-1 Na, K, Ca, Mg, or a mixture of them were used as synthetic matrices. Germanium, In and Y were tested as internal standards. Best recoveries were achieved when 1 mg L-1 of In was used as internal standard. The values of D3,2 and D50 parameters demonstrated that the aerosol produced by using FB®MN has smaller drops than the aerosol produced by using Micromist®. In this study the FB®MN was also used for generation of As and Se XV hydrides directly into the aerosol formed inside the nebulization chamber before detection by ICP OES. The FB®MN allowed the hydrides generation directly into the spray chamber without using any additional device either for solution and gases control or for gas phase separation. Synthetic solutions containing As and Se plus Ca, Mg and K were used for evaluating hydride generation. Germanium, In and Y were tested as internal standards. Accuracy was assessed using addition-recovery experiments in synthetic solutions. Best recoveries for all media were achieved when Ge was used as internal standard. Limits of detection (LOD, 3σ blank) of 2.7 and 5.8 μg L-1 were obtained for As (228.812 nm) and Se (196.016 nm), respectively, when keeping the nebulization gas flow rate at 0.6 L min-1 and the liquid flow rate at 0.67 mL min-1.Universidade Federal de Sao CarlosEste projeto de pesquisa visou avaliar diferentes estratégias para correção de interferências espectrais e não espectrais na determinação de As e Se por espectrometria de emissão óptica com plasma acoplado indutivamente (ICP OES) e espectrometria de massa com plasma acoplado indutivamente (ICP-MS). As medidas dos isótopos 75As+ e 80Se+ em ICP -MS são fortemente afetadas pela presença dos interferentes poliatômicos 40Ar35Cl+ e 40Ar2 +, respectivamente. Esses processos podem ser resolvidos usando estratégias de preparo de amostra, plasma frio e, mais modernamente, interfaces com sistemas de colisões e reações. Foi estudada como ferramenta para remoção de interferências espectrais a introdução de diferentes gases (H2 e He) nos cones de amostragem e skimmer presentes na interface de colisão e reação (CRI). A introdução do gás H2 através do cone skimmer foi mais eficiente na remoção dos interferentes poliatômicos. Os melhores limites de detecção (LOD) 0,019 e 0,097 ng mL-1 para os isótopos 75As+ e 80Se+, respectivamente, foram obtidos introduzindo 80 mL min-1 de H2 no cone skimmer. A exatidão foi comprovada empregando dois materiais de referência certificado, Tecido de ostra e Tecido de molusco. Os efeitos de matriz podem ser atenuados usando estratégias de calibração adequadas, tais como a utilização de um padrão interno ou calibração com adições de padrão. Para determinação de As e Se por ICP OES foi avaliado o multinebulizador Flow Blurring (FB®MN) para corrigir efeitos de matriz e reduzir interferências empregando a estratégia de calibração em linha. O aerossol gerado pelo FB®MN foi caracterizado e comparado com o aerossol gerado por um nebulizador pneumático convencional (Micromist®). Soluções contendo 0,050 e 0,10 mol L-1 de Na, K, Ca, Mg e uma mistura de todos esses elementos foram usadas neste estudo. Na calibração externa e on-line foram testados os elementos Ge, In e Y como padrão interno. Melhores valores de recuperação para As e Se foram obtidos utilizando-se solução 1 mg L-1 de In como padrão interno. Os valores dos parâmetros D3,2 e D50 demonstraram que o aerossol produzido pelo FB®MN se caracteriza por gotas com menores diâmetros comparativamente ao aerossol gerado pelo MicroMist®. Neste estudo também foi avaliado a formação de espécies voláteis na câmara de nebulização para determinação de As e Se por ICP OES utilizando o FB®MN ao invés de qualquer dispositivo para controle de soluções e gases ou separação da fase gasosa. Soluções contendo As e Se em meio de Ca, Mg e K foram usadas para avaliar a geração de hidretos. Germânio, índio e ítrio foram testados como padrão interno. A exatidão foi avaliada usando testes de adição e recuperação em soluções sintéticas. Melhores recuperações para todos os meios foram alcançadas quando o Ge foi utilizado como padrão interno. Os limites de detecção (LOD s 3σ branco) alcançados utilizando o sistema FB®MN e geração de hidretos foram de 2,7 e 5,8 g L-1 para As (228,812 nm) e Se (196,016 nm), respectivamente, quando a vazão de nebulização foi de 0,6 L min-1 e vazão de líquido de 0,67 mL min-1

Use of in vitro digestion method and theoretical calculations to evaluate the bioaccessibility of Al, Cd, Fe and Zn in lettuce and cole by inductively coupled plasma mass spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Theoretical calculations of the binding energies of metal-polyphenols and metal-cellulose, as well as the hydration energies of metal-polyphenols were used to support the results obtained for the bioaccessibility of aluminium, cadmium, iron and zinc from four types of lettuce and one type of cole that were evaluated using an in vitro gastrointestinal digestion model and inductively coupled plasma-mass spectrometry. The bioaccessibility of Al found in the vegetables were less than 11% of the total Al content, whereas Cd exhibited average bioaccessibility of approximately 14% for the fresh samples and 41% considering the dried vegetables studied. However, the results indicated average bioaccessibility of 35% and 26% for Zn and average bioaccessibility of 19% and 21% for Fe in fresh and dried samples, respectively. The low bioaccessibility of Al is due to its strong binding with all of the vegetable components, whereas the low bioaccessibility of Fe and Zn are due to their interactions with phytates. Cd was observed to be the most bioaccessible element in the dried samples because of its weak interaction with other compenents in the vegetables. (C) 2014 Elsevier B.V. All rights reserved.Theoretical calculations of the binding energies of metal-polyphenols and metal-cellulose, as well as the hydration energies of metal-polyphenols were used to support the results obtained for the bioaccessibility of aluminium, cadmium, iron and zinc from119152158FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)2013/26855-2; 2012/15020-4; 2008/57808-1573894/2008-6The authors gratefully acknowledge the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP Process 2013/26855-2 and Process 2012/15020-4), the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and National Institute of Advance