The contamination of natural environments by trace metals has several adverse effects on human health, which is mainly due to the high toxicity, persistence and reactivity of these species in the environment. To understand the bioavailability of trace metals, it is necessary to know the speciation in equilibrium and the dynamic behavior of the system. In this context, the present work aims to present a bibliographic review about the potentialities of the Stripping Chronopotentiometry (SCP) and Stripping Chronopotentiometry at Scanned Deposition Potential (SSCP) in the study of dynamic trace metal speciation. These techniques have low detection limits and do not suffer interference due to the adsorption of organic matter on the surface of the working electrode. Coupling these techniques with the Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) enables simultaneous determination of free ions, complexation equilibrium constants and diffusion coefficients of the complexes, thus providing information on the dynamic and heterogeneity of the metal complexes in the presence of macromolecules or particles. In this paper we will present the theory of dynamic speciation of trace metals, a detailed description of how to use the techniques to obtain this information, and examples of application in model systems and natural samples.

This work presents a critical overview of the NICA-Donnan model for trace metal thermodynamic speciation with humic substances obtained from natural organic matter in soils, natural waters and anthropogenic sources. A first part covers the theoretical aspects of the model, how to obtain good experimental data and perform the modelling. A second part deals with the developments in the last decade namely the use of the generic parameters, criticism and alternatives to the electrostatic modeling, the understanding of the NICA equation and an analysis of the published data, ending with the needs and opportunities for model development.

RESUMO Considerando a possibilidade de que os agrotóxicos utilizados nas principais culturas, como soja, algodão e milho, podem gerar resíduos que contaminam o meio ambiente, faz-se necessária uma análise preliminar sobre a possibilidade de contaminação das águas subterrâneas por resíduos de agrotóxicos utilizados nas principais regiões agrícolas do país. Uma dessas áreas agrícolas se localiza na cidade de Campo Novo do Parecis, Mato Grosso, região de estudo deste trabalho. Os principais agrotóxicos aplicados nas diferentes culturas da região foram avaliados quanto às suas propriedades físico-químicas, seus potenciais de contaminação de acordo com critérios da Agência de Proteção Ambiental dos Estados Unidos e pelo índice de vulnerabilidade de águas subterrâneas (GUS). As informações obtidas foram empregadas para avaliar o risco de contaminação das águas subterrâneas. De acordo com os resultados encontrados, a região apresenta risco real de contaminação ambiental por resíduos de agrotóxicos, uma vez que 45,6% dos agrotóxicos comumente empregados na agricultura local são classificados como extremamente tóxicos ou altamente tóxicos. Além disso, vários desses ingredientes aditivos, cerca de 22%, já foram detectados em diferentes compartimentos ambientais de outras regiões do estado de Mato Grosso.

ABSTRACT Considering the possibility that pesticides used in main crops, such as soybeans, cotton and corn, generate toxic residues that contaminate the environment, a preliminary analysis of the possibility of groundwater contamination is necessary in the main agricultural regions in Brazil. One of these agricultural areas is located in Campo Novo do Parecis, Mato Grosso, the study area of this work. The main pesticides used in different cultures of this region were evaluated considering their physicochemical properties, their contamination potentials according to criteria of the Environmental Protection Agency of the United States and the groundwater ubiquity score index (GUS). The information obtained was used to assess the risk of groundwater contamination. According to the results, the region presents a real risk of environmental contamination by pesticide residues, since 45.6% of the pesticides commonly used in local agriculture are classified as extremely toxic or highly toxic. In addition, several of these pesticides, about 22%, have been detected in different environmental compartments from other regions of the state of Mato Grosso, Brazil.

O objetivo deste trabalho foi estudar a adsorção de micronutrientes em humina e verificar a capacidade de liberação desses elementos em água. O primeiro passo foi determinar a capacidade de adsorção da humina para alguns micronutrientes essenciais para as plantas e determinar alguns parâmetros cinéticos. A ordem de adsorção foi Zn < Ni < Co < Mn < Mo < Cu < Fe, sendo que Zn apresentou valores máximos de ca. 2,5 mg g-1 e Fe valores de ca. 0,5 mg g-1, para os sistemas contendo 1 g de humina. O ferro apresentou maiores percentuais de liberação (ca. 100%) e Co apresentou percentuais mais baixos (0,14%). Infere-se a partir dos resultados que o uso de humina enriquecida com micronutrientes pode ser uma alternativa promissora para a fertilização de solos agrícolas, com o benefício adicional de incorporar a matéria orgânica presente na forma de substâncias húmicas no solo e melhorar a produtividade agrícola.

The objective of this work was to investigate the adsorption of micronutrients in humin and to verify the ability to release these elements in water. The first step was to determine the adsorption capacity of humin for several essential plant micronutrients and check the kinetic parameters. The order of adsorption was Zn < Ni < Co < Mn < Mo < Cu < Fe, whereas Zn showed maximum values of ca. 2.5 mg g-1 and Fe values of ca. 0.5 mg g-1 for systems containing 1 g of humin. Iron presented higher percentages of release (ca. 100%) and Co the lowest percentages (0.14%). The findings suggested that the use of humin enriched with micronutrients can be a promising alternative for the fertilization of agricultural soils, with the additional benefit of incorporating organic matter present in the form of humic substances into the soil and improving the agricultural productivity.

In this study, polymeric nanocapsules of PCL containing the herbicide atrazine were prepared. In order to optimize the preparation conditions, a 2³ factorial design was performed using different formulations of nanocapsules, which investigated the influence of three variables at two levels. The factors varied were the quantities of PCL, Span 60 and Myritol. The results were evaluated considering the size, polydispersity, zeta potential and association rate and the measures of these parameters were taken immediately after preparation and after 30 days of preparation. The formulations with minimum level of polymer in the preparation showed better stability results.

Agrochemicals constitute the class of products most commonly found in water resources. Their high level of concentration is due to the fact that less than 0.1% of pesticides applied to crops reach their target. The present work aims to study the sorption of clomazone herbicide (associated or not with nanoparticles). The sorption tests, performed with the 2(4) factorial design, showed that the form of herbicide is the main factor for sorption of clomazone. The application of nanoparticles as delivery system for agrochemicals is a pressing area of study and can contribute for decrease in effects of clomazone in the environment.

Interações entre substâncias húmicas aquáticas (SHA), de rios tropicais, e dois interferentes endócrinos (IE) foram estudados utilizando sistema de ultrafiltração em fluxo tangencial equipado com membrana de celulose de 1 kDa com a finalidade de separar os IE livres da fração ligada as SHA. A quantificação de 17α-etinilestradiol e bisfenol A foi realizada utilizando cromatógrafo a gás acoplado a espectrômetro de massas (GC-MS). O tempo de equilíbrio entre as SHA e IE foi de aproximadamente 30 min, e as capacidades complexantes do 17α-etinilestradiol e bisfenol A foram em torno de 18,53 e 2,07 mg g-1 de carbono orgânico total (COT), respectivamente. A maior interação das SHA ocorreu para 17α-etinilestradiol, em relação ao bisfenol A, devido a presença de hidrogênio na estrutura do 17α-etinilestradiol, que podem interagir com os grupos oxigenados presentes nas SHA. Os resultados indicam que as SHA podem influenciar fortemente no transporte e reatividade dos interferentes endócrinos presentes em sistemas aquáticos

Interactions between two endocrine disruptors (ED) and aquatic humic substances (AHS) from tropical rivers were studied using an ultrafiltration system equipped with a 1 kDa cut-off cellulose membrane to separate free ED from the fraction bound in the AHS. Quantification of 17α-ethynylestradiol and bisphenol A was performed using gas chromatography-mass spectrometry (GC-MS). The times required for establishment of equilibrium between the AHS and the ED were ca. 30 min, and complexation capacities for 17α-ethynylestradiol and bisphenol A were 18.53 and 2.07 mg g-1 TOC, respectively. The greater interaction of AHS with 17α-ethynylestradiol, compared to bisphenol A, was due to the presence of hydrogen in the structure of 17α-ethynylestradiol, which could interact with ionized oxygenated groups of the AHS. The results indicate that AHS can strongly influence the transport and reactivity of endocrine disruptors in aquatic systems.

The knowledge of the structure characteristic of the Organic Matter is important for the understanding of the natural process. In this context aquatic humic substances (principal fraction) were isolated from water sample collected from the two distinct rivers, using procedure recommended for International Humic Substances Society and characterized by elemental analysis, electron paramagnetic resonance and nuclear magnetic resonance (13C NMR). The results were interpreted using principal component analysis (PCA) and the statistical analyses showed different in the structural characteristics of the aquatic humic substances studied.

In this paper, we describe the preparation of alginate nanoparticles as a delivery system for the herbicide clomazone. Two different methods were investigated and characterized by size distribution, zeta potencial, pH and in vitro release. The alginate/AOT nanoparticles had higher rates of association of the herbicide clomazone than alginate/chitosan nanoparticles. Clomazone release profile, showed a significant difference in release behavior of pure herbicide in solution when compared with herbicide loaded in both alginate nanoparticles. This study is important to construct a biodegradable release system using herbicide for later release into more specific targets, avoiding contamination of environmental matrices.

Cellulose acetate polymeric membranes had been prepared by a procedure of two steps, combining the method of phase inversion and the technique of hydrolysis-deposition. The first step was the preparation of the membrane, and together was organomodified with tetraethylortosilicate and 3-aminopropyltrietoxysilane. Parameters that exert influence in the complexation of the metallic ion, as pH, time of complexation, metal concentration, had been studied in laboratory using tests of metal removal. The membranes had presented resistance mechanics and reactivity to cations, being able to be an alternative for the removal, daily pay-concentration or in the study of the lability of metals complexed.

In this paper we describe the preparation poly (L-lactide) (PLA) nanocapsules as a drug delivery system for the local anesthetic benzocaine. The characterization and in vitro release properties of the system were investigated. The characterization results showed a polydispersity index of 0.14, an average diameter of 190.1± 3 nm, zeta potential of -38.5 mV and an entrapment efficiency of 73%. The release profile of Benzocaine loaded in PLA nanocapsules showed a significant different behavior than that of the pure anesthetic in solution. This study is important to characterize a drug release system using benzocaine for application in pain treatment.

Neste trabalho substâncias húmicas (SH) extraídas de solos não alagáveis (Araçá) e alagáveis (Iara) foram caracterizadas com cálculos de estabilidade e energias de ativação associadas com a desidratação e decomposição térmica de SH utilizando TGA and DTA, ressonância paramagnética eletrônica (EPR) e razões atômicas C/H, C/N e C/O. Para SH extraídas de solos alagáveis, existe evidências da influência da umidade sobre o processo de humificação da matéria orgânica. Observações do comportamento térmico, com análise elementar, indicaram a presença de fósseis de carbono orgânico nas partículas de argila, o que só decompõe acima de 800 ºC. Essa característica pode explicar as diferentes estabilidades térmicas e energias de ativação requeridas na pirólise para amostra Iara comparada a amostra Araçá.

In this work humic substances (HS) extracted from non-flooded (Araçá) and flooded (Iara) soils were characterized through the calculation of stability and activation energies associated with the dehydration and thermal decomposition of HS using TGA and DTA, electronic paramagnetic resonance and C/H, C/N and C/O atomic ratios. For HS extracted from flooded soils, there was evidence for the influence of humidity on the organic matter humification process. Observations of thermal behaviour, with elemental analysis, indicated the presence of fossilized organic carbon within clay particles, which only decomposed above 800 ºC. This characteristic could explain the different thermal stability and pyrolysis activation energies for Iara HS compared to Araçá HS.

Bupivacaine (S75-R25, NovaBupi®) is an amide type local anesthetic widely used. The present work consists of the development and validation of analytical methodology for evaluation of NovaBupi® content in the poly-lactide-co-glycolide nanospheres (PLGA-NS) by high performance liquid chromatography. The separation was made using the reversed-phase column LC-18, acetonitrile/phosphate buffer 85:15 v/v as mobile phase and detection at 220 nm. The results obtained show that the analytical methodology is accurate, reproducible, robust and linear over the concentration range 10-220.0 g/mL of NovaBupi®. The method was applied to determine the encapsulation efficiency and evaluate the release profile of NovaBupi®, showing good results.

In this work commercial filters papers were organomodified with tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (3-APTS), aiming at the development of a new analytical procedure for in-situ speciation of labile and inert metal species in aquatic systems. Parameters that exert influence on the metal lability such as pH, chelating time, concentration and characteristics of the organic matter were studied in the laboratory using tests for metal recuperation. The results showed slower kinetics for Cu ion than for Ni, Mn and Cd in the absence of aquatic humic substances (AHS). The relative lability observed for complexed metals in aquatic humic substances using organomodified filter papers was Cu>>Cd>Ni>Mn. The pH values, structural characteristics and concentration of AHS exert strong influence on the lability of the metals. The results obtained showed that the utilization of organomodified filter papers can be an interesting and promising alternative for in situ characterization of metal lability in aquatic systems.

O objetivo deste trabalho foi comparar a complexação de substâncias húmicas (SH) e alfa-aminoacidos (metionina, metionina sulfoxido e cloridrato de cisteína) por elementos traço de interesse biológico (Al, Cu, Pb, Mn, Zn, Cd e Ni). Sistema de ultrafiltração tangencial foi utilizado para diferenciação entre os complexos SH-metal e alfa-aminoácidos-metal. As determinações de metal foram feitas utilizando ICP-OES. Os resultados mostraram que as SH podem ser consideradas agentes complexantes seletivos com alta capacidade de complexação a Al, Cu e Pb, podendo ser clinicamente importante.

The aim of the present work was to carry out experimental comparison between humic substances (HS) and representative alpha-amino acids (methionine, methionine sulfoxide and cysteine hydrochloride) in relation to the complexation of biologically active trace elements (Al, Cu, Pb, Mn, Zn, Cd and Ni). A mobile time-controlled tangential-flow UF technique was applied to differentiate between HS-metal and alpha-aminoacids-metal complexes. Metal determinations were conventionally carried out using a ICP-OES. The results showed that HS may be considered as a selective complexing agents with higher metal bonding capability in relation to Al, Cu and Pb, the fact that may be clinically important.