Luciana Melo Coelho

Determination of arsenic compounds in beverages by high-performance liquid chromatography-inductively coupled plasma mass spectrometry.

Arsenic compounds including arsenous acid (As(III)), arsenic acid (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were separated by high-performance liquid chromatography (HPLC) and detected by inductively coupled plasma mass spectrometry (ICP-MS). A Hamilton PRX-100 anionic-exchange column and a pH 8.5 K(2)HPO(4)/KH(2)PO(4) 5.0x10(-3)molL(-1) mobile phase were used to achieve arsenic speciation. The separation of arsenic species provided peaks of As(III) at 2.75min, DMA at 3.33min, MMA at 5.17min and As(V) at 12.5min. The detection limits, defined as three times the standard deviation of the lowest standard measurements, were found to be 0.2, 0.2, 0.3 and 0.5ngmL(-1) for As(III), DMA, MMA and As(V), respectively. The relative standard deviation values for a solution containing 5.0mugL(-1) of As(III), DMA, MMA and As(V) were 1.2, 2.1, 2.5 and 3.0%, respectively. This analytical procedure was applied to the speciation of arsenic compounds in drinking (soft drink, beer, juice) samples. The validation of the procedure was achieved through the analysis of arsenic compounds in water and sediment certified reference materials.

Determination of Cd, Cu, and Pb after Cloud Point Extraction using Multielemental Sequential Determination by Thermospray Flame Furnace Atomic Absorption Spectrometry (TS‐FF‐AAS)

Abstract In the present paper a procedure for simultaneous preconcentration of Cd, Cu, and Pb using cloud point extraction (CPE) and multielemental sequential determination by thermospray flame furnace atomic absorption spectrometry (TS‐FF‐AAS) is proposed. This preconcentration procedure is based on the metals extraction into micellar media of octylphenoxypolythoxyethanol (Triton X‐114) after their reaction with 1‐(2‐pyridylazo)‐2‐naphtol (PAN). A Box‐Behnken design was used to optimize the variables (pH, buffer concentration and volume of NaCl) involved in the extraction procedure. Enrichment factors were calculated as the ratio between the slopes of calibration equations with and without the preconcentration procedure in the TS‐FF‐AAS, with values of 59, 25, and 21 respectively for Cd, Cu, and Pb. Limits of detection (LOD) (3sb, n=10) were also calculated as 0.025, 0.38, and 0.43 µg L−1 to Cd, Cu, and Pb, respectively. The precision (repeatability) expressed as relative standard deviation (RSD, n=10) for reference standards of 10.0 and 20.0 µg L−1 were 6.1 and 4.5% for Cd, 7.2 and 3.4% for Cu and 5.2 and 8.7% for Pb. The accuracy was confirmed through the analysis of certified reference material (NIST 1643d, Trace elements in water). The developed procedure was also applied to Cd, Cu, and Pb determinations in mineral water samples.

Bioremediation of Waters Contaminated with Heavy Metals Using Moringa oleifera Seeds as Biosorbent

Water is not only a resource, it is a life source. It is well established that water is important for life. Water is useful for several purposes including agricultural, industrial, household, recreational and environmental activities. Despite its extensive use, in most parts of the world water is a scarce resource. Ninety percent of the water on earth is seawater in the oceans, only three percent is fresh water and just over two thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air. Thus, almost all of the fresh water that is available for human use is either contained in soils and rocks below the surface, called groundwater, or in rivers and lakes.

Bioremediation of Polluted Waters Using Microorganisms

Water pollution is an issue of great concern worldwide, and it can be broadly divided into three main categories, that is, contamination by organic compounds, inorganic compounds (e.g., heavy metals), and microorganisms. In recent years, the number of research studies concerning the use of efficient processes to clean up and minimize the pollution of water bodies has been increasing. In this context, the use of bioreme‐ diation processes for the removal of toxic metals from aqueous solutions is gaining considerable attention. Bioremediation can be defined as the ability of certain biomolecules or types of biomass to bind and concentrate selected ions or other molecules present in aqueous solutions. Bioremediation using microorganisms shows great potential for future development due to its environmental compatibility and possible cost-effectiveness. A wide range of microorganisms, including bacteria, fungi, yeasts, and algae, can act as biologically active methylators, which are able to at least modify toxic species. Many microbial detoxification processes involve the efflux or exclusion of metal ions from the cell, which in some cases can result in high local concentrations of metals at the cell surface, where they can react with biogenic ligands and precipitate. Although microorganisms cannot destroy metals, they can alter their chemical properties via a surprising array of mechanisms. The main purpose of this chapter is to provide an update on the recent literature concerning the strategies available for the remediation of metal-contaminated water bodies using microorganisms and to critically discuss their main advantages and weaknesses. The focus is on the heavy metals associated with environmental contamination, for

Non-chromatographic methods focused on speciation of arsenic and selenium in food and environmental samples

Abstract Speciation is a promising and essential tool in the evaluation of the contamination of metals in food and environmental samples. In this context, information about the species of these elements is important considering that toxic effects are directly related to their chemical forms. The enormous progress in combining separation and detection techniques has enabled the effective chemical speciation. However, a possible source of error in studies of speciation occurs during sample preparation. Appropriate treatment of samples is necessary in order to ensure that interconversion between the species does not occur during the experimental procedure prior to the final analysis. In this review, methods of sample preparation for the determination of arsenic and selenium in food and environmental samples are discussed. We decided to focus on these elements since they account for around 50% of all speciation studies. Procedures including conventional extraction, microwave-assisted extraction and sonolysis are discussed as simple ways to ensure species selectivity. The main purpose of this review is to provide an update on the recent literature concerning the strategies for arsenic and selenium speciation and to critically discuss their advantages and weaknesses compared with the commonly accepted approach of combining non-chromatographic and spectroscopic techniques. The problems focused on involve sampling, sample preparation and storage, as well as changes in ‘species information’ that occur during the use of various separation technologies. These difficulties are described along with recent developments aimed at overcoming these potential issues.

On-line bi-directional electrostacking for As speciation/preconcentration using electrothermal atomic absorption spectrometry

A method using bi-directional electrostacking (BDES) in a flow system is presented for As preconcentration and speciation analysis. Some parameters such as electrostacking time and applied voltage, support buffers and their concentrations were investigated. Boric acid plus sodium hydroxide at 0.1mol/l concentration was selected as support buffer to improve the pre-concentration factor (PF) for As(V). An analytical range from 2.0 to 50.0mugl(-1), and 0.35mugl(-1) as limit of detection, when applied 750V for 20min, were achieved. Under these conditions, a pre-concentration factor of 4.8 was obtained. The proposed method was applied to determine As(V) in mineral water and natural water samples (river, fountain and gold mine) from Ouro Preto city. Recoveries from 93.5 to 106.4% were achieved at 10mugl(-1) added As level (R.S.D.s between 3 and 7%). Potassium permanganate (10mgl(-1)) was used for oxidising As species in order to determine total As, being established the concentration of As(III) from the difference between total As and As(V).

Analytical Strategies for the Determination of Arsenic in Rice

Arsenic is an element of concern given its toxicological significance, even at low concentrations. Food is a potential route of exposure to inorganic arsenic and in this regard arsenic in rice is associated with soil contamination, fertilizer application, and the use of arsenic-containing irrigation water. Therefore, there is a need to investigate the regional rice crops with a view to future discussions on the need for possible regulatory measures. Several studies have reported high concentrations of arsenic in rice grown in soils irrigated with contaminated water; however, procedures used, including sample pretreatment and preconcentration steps, have to be followed to ensure sensitivity, accuracy, and reproducibility. Arsenic is a difficult element to measure in complex matrices, such as foods, because the matrix must be destroyed at an elevated temperature without the loss of the analyte or contamination. This review summarizes the major methods for the determination of arsenic in rice samples. The main purpose of this review is to provide an update on the recent literature concerning the strategies for the determination of arsenic and to critically discuss their advantages and weaknesses. These difficulties are described along with recent developments aimed at overcoming these potential issues.

Strategies to increase selectivity of analytical methods for As, Cr and Se speciation in biological samples: A review

Abstract This review provides an overview and discusses different analytical strategies that minimize or eliminate the preparation of samples for speciation of organic and inorganic species of As, Cr and Se in samples of biological interest. These metals are important for the human body and the presence of various chemical forms of metals determines its essentiality and toxicity, thus speciation comes as an important tool for the study of biological samples. However, speciation requires a reduction in the steps of sample preparation, allowing a sample investigation in its most native form in order to reduce the changes in chemical species. The strategies proposed for speciation of these metals include: solid phase extraction, point cloud extraction, suspension and direct analysis. Selected methods proposed for the speciation of organic and inorganic species of As, Cr and Se were reviewed including their main figures of merit, advantages and disadvantages

Utilização de adsorvente natural para remoção do hormônio etnilestradiol

Resumo: Os contaminantes emergentes tem sido uma classe de compostos que merecem grande atenção devido a poluição que vem ocasionando mesmo em concentração mínima. Neste contexto, o uso de materiais alternativos torna-se uma fonte viável para despoluição do meio ambiente. Sendo assim, neste trabalho realizou-se o estudo da remoção do etnilestradiol (EE2) utilizando o adsorvente Typha tratado em meio ácido (Typha HCl). Através dos resultados é possível inferir que o material alcança uma eficiência de remoção de até 80%, devido as inúmeras interações possíveis entre adsorvente e adsorvato, tornando este material economicamente viável, além de ser uma fonte renovável e de fácil identificação e localização para uma possível utilização.

Estudo cinético da adsorção do antibiótico sulfametoxazol pela casca de arroz in natura

Resumo: Neste trabalho estudou-se a cinética de adsorção do contaminante sulfametoxazol pela casca de arroz, na busca de um adsorvente alternativo que além de contribuir para a descontaminação ambiental, é considerado como um possível recurso de baixo custo. A casca de arroz foi preparada adequadamente em laboratório, sendo as curvas cinéticas obtidas em diferentes taxas de agitação do sulfametoxazol com o material adsorvente. A cinética foi avaliada de acordo com os modelos de pseudo-primeira ordem, pseudo-segunda-ordem e de difusão intrapartícula, definindo qual se ajusta melhor aos dados experimentais. Através dos resultados de cinética observou-se adequação ao modelo de pseudo-segunda ordem e que a difusão intrapartícula não é o único recurso de adsorção, pois ocorrem outras interações entre adsorvente e adsorvato. Os resultados demonstraram que a casca de arroz é um adsorvente alternativo de baixo custo com capacidade satisfatória para remover o sulfametoxazol.