Editorial |
Artigo Inactivation of Escherichia coli and Pseudomonas sp. by photocatalytic oxidation Cordeiro, Angela Cristina de Souza Leite, Selma Gomes Ferreira Dezotti, Márcia Abstract in English: This study presents the bactericidal activity of titanium dioxide photocatalysis, using as model Escherichia coli and Pseudomonas sp. cells. It was observed that the process efficiency is related to initial cell concentration, light intensity, UV irradiation exposure time, TiO2 concentration increase. The ultimate removal efficiency was above 99.9%. |
Artigo Microwave-assisted photochemical digestion of natural waters: application in partition and speciation studies of copper Sodré, Fernando F. Peralta-Zamora, Patricio G. Grassi, Marco T. Abstract in English: The efficiency of a new procedure for the digestion of natural waters, based on a microwave-activated photochemical reactor was evaluated in this work. Fluorescence spectra showed a 99% reduction in the emission of a 40 mg L-1 humic acid solution after 15 min of UV irradiation. In the presence of H2O2, only 3 min were necessary to accomplish a reduction of almost 100% in the emission and 6 min to reduce the concentration of dissolved organic carbon by 95%. The copper recovery from synthetic samples containing commercial humic acid, from soil suspensions, as well as from natural waters varied between 91.5 and 106.6%. The digestion of dissolved and unfiltered samples was successfully accomplished in 6 and 12 min, respectively. No contaminations or sample losses were observed. Results of copper speciation in natural waters showed that this metal is predominantly bound to natural ligands. Only 3-6% of the total recoverable copper is present in the labile form. |
Artigo Determination of the critical micelle concentration of humic acids by spectroscopy and conductimetric measurements Moraes, Solange Leite de Rezende, Maria Olímpia Oliveira Abstract in English: The aim of this study was the determination of the critical micelle concentration (CMC) of the sodium dodecyl sulfate (SDS) surfactant using spectroscopic and conductimetric determinations and to compare these methodologies in the determination of the CMC of different humic acids (HA). The CMC obtained by conductimetric determination was satisfactory. By spectroscopic determination two values of the CMC were obtained for HA. These values can be to due the intra and intermolecular interactions in the HA structure. |
Morphological study of Sr2CeO4 blue phosphor with fine particles Gomes, Janaína Pires, Ana Maria Serra, Osvaldo Antonio Abstract in English: Morphological and spectroscopic studies of Sr2CeO4 blue phosphor in the form of fine particles prepared from a powdered multi-component precursor, via a combustion method, are reported. Samples were also prepared through a solid-state reaction and from a polymeric precursor for comparison. Citric acid or glycine as fuels in the combustion method lead to a mixture which is heated at 950 ºC for 4 h, resulting in spheroidal particles with a diameter between 250-550 nm. Samples from the polymeric precursor result in spheroidal particles (350-550 nm) and from the solid-state reaction in irregular particles (~ 5 mum). Therefore, the combustion method is adequate for preparation of Sr2CeO4 in the form of spherical fine particles. |
Artigo Synthesis, characterization and spectroscopic properties of [Ln<FONT FACE=Symbol>Ì</FONT>(bipy)2py(CO2Et) 2]3+ lanthanide cryptates Nova, Suzana P. Vila Pereira, Giovannia A. de L. Sá, Gilberto F. de Alves Júnior, Severino Bazin, Hervé Autiero, Hervé Mathis, Gérard Abstract in English: This work reports on the synthesis, characterization (infrared and hidrogen nmr spectra) and photophysical properties (luminescence spectra and emission quantum yield) of the lanthanide cryptates [Ln<FONT FACE=Symbol>Ì</FONT>(bipy)2py(CO2Et) 2]3+ with Ln = Eu3+, Tb3+ or Gd3+, which can be applied as efficient Light-Conversion-Molecular-Devices. From emission spectra of [Eu<FONT FACE=Symbol>Ì</FONT>(bipy)2py(CO2Et) 2]3+ it was possible to assign C3 symmetry to the metal ion. The spectroscopic studies show a higher emission quantum yield (q=25%) for [Tb<FONT FACE=Symbol>Ì</FONT>(bipy)2py(CO2Et) 2]3+ in aqueous solution, whereas the europium cryptate presents q=14%. This is justified by a more efficient energy transfer between triplet and emission levels of terbium (T->5D4). |
Artigo Coagulation/flocculation of suspensions of iron oxide particles by aluminum sulphate Guedes, Claudia Dumans Pereira, Jomara G. Lena, Jorge C. de Paiva, José Fernando de Lima, Rosa Malena F. Abstract in English: The destabilization mechanism of suspensions of positively charged iron oxide particles by aluminum sulphate was investigated, aiming to evaluate the efficiency of the latter as a coagulant for natural surface waters from iron ore mining plants. Synthetic waters that simulate natural suspensions were used. The best coagulant dosage was found to be 100 mg/L at pH 4. The specific adsorption of hydrolysis products of aluminum salts on iron oxide particles and heterocoagulation processes involving differently charged substrates are proposed to explain the turbidity reduction of the suspensions. |
Artigo Parameter optimization for pesticide multiresidue determination using SPME in water samples Komatsu, Emy Vaz, Jorge Moreira Abstract in English: In this study the factors that affect the extraction of pesticide residues from water samples for their determination by solid-phase micro-extraction (SPME) and GC/MS were optimized. The fiber polymer, the extraction mode, the ionic strength, the stirring rate, the pH and the extraction time were the most significant parameters evaluated. The recovery obtained with the proposed method ranged from 94 to 110% and the sensitivity of the method, determined by calculating the detection limit (DL), ranged from 0.004 to 0.1 mug l-1. The results obtained with spiked real samples, at the 0.1 mug l-1 level, showed acceptable conformity with the expected values. |
Artigo Optimization of the carbon paste electrode preparation containing riboflavin immobilized on an inorganic support Pereira, Arnaldo César Kubota, Lauro Tatsuo Abstract in English: The aim of this work was to optimize the preparation of electrodes with riboflavin (RF) immobilized on a silica surface modified with niobium oxide and carbon paste. Electrode preparation was optimized employing a factorial design consisting of two levels and three factors. The electrochemical properties of immobilized RF were investigated by cyclic voltammetry. The factorial analysis was carried out analysing the current intensity (Ipa). It was possible to optimize the electrode to get the best reversibility in the redox process, i. e. the lowest separation between anodic and cathodic peak potentials and a current ratio close to unity. The concentration of supporting electrolyte has a small effect. The proportion has the highest effect and the interaction factor between proportion and mixture has also a significant effect on the current intensity. |
Artigo Extraction of Al(III), Cr(III) and Fe(III) from ethanolic medium by anilinepropylsilica xerogel Pavan, Flávio A. Costa, Tania M. H. Benvenutti, Edilson V. Jacques, Rosângela A. Córdova, Manuela C. Abstract in English: In this study, the preparation of the xerogel anilinepropylsilica is reported. The ability of the xerogel for extracting Al(III), Cr(III) and Fe(III) from ethanol was investigated at 25 ºC. The xerogel adsorption capacities were obtained from the adsorption isotherms by using the batch method. Flame atomic absorption spectrometry (FAAS) was used to estimate the concentration of metal ions in solution. The adsorption affinity follows the series Cr(III) > Fe(III) > Al(III) and the maximum adsorption capacities of the metal ions were 0.61, 0.52 and 0.43 mmol g-1, respectively. |
Artigo Heavy metals removal from wastewater by the natural zeolite scolecite - temperature and pH influence in single-metal solutions Jimenez, Ricardo Sarti Dal Bosco, Sandra Maria Carvalho, Wagner Alves Abstract in English: Cation exchange capabilities of a Brazilian natural zeolite, identified as scolecite, were evaluated for application in wastewater control. We investigated the process of sorption of chromium(III), nickel(II), cadmium(II) and manganese(II) in synthetic aqueous effluents, including adsorption isotherms of single-metal solutions. The natural zeolite showed the ability to take up the tested heavy metals in the order Cr(III) > Cd(II) > Ni(II) > Mn(II), and this could be related to the valence and the hydration radius of the metal cations. The influence of temperature (25, 40 and 60 ºC) and initial pH value (from 4 to 6) was also evaluated. It was found that the adsorption increased substantially when the temperature was raised to 60 ºC and that maximum adsorption capacity was observed at pH 6. These results demonstrate that scolecite can be used for removal of heavy metals from aqueous effluents, under optimized conditions. |
Artigo Determination of organochlorated pesticides in the water supply system, drinking water and soil of the region of Bauru (SP) Rissato, Sandra Regina Libânio, Marcelo Giafferis, Giselda Passos Gerenutti, Marli Abstract in English: This paper evaluates the presence of organochlorinated pesticides in the water supply system of the city of Bauru, State of São Paulo, Brazil. Soil samples were collected in agricultural areas and water samples at several points of the water source (river) and the distribution net. The results of the analyses of the water from the source were compared with the Brazilian classification system for inland waters (CONAMA/86) and the results of analyses of treated water were compared with Brazilian standards for finished drinking water. |
A simplified procedure for determination of clofentezine residues in fruits by liquid chromatography with UV detection Navickiene, Sandro Ribeiro, Maria Lúcia Abstract in English: A rapid and sensitive method is described for the determination of clofentezine residues in apple, papaya, mango and orange. The procedure is based on the extraction of the sample with a hexane:ethyl acetate mixture (1:1, v/v) and liquid chromatographic analysis using UV detection. Mean recoveries from 4 replicates of fortified fruit samples ranged from 81% to 96%, with coefficients of variation from 8.9% to 12.5%. The detection and quantification limits of the method were of 0.05 and 0.1 mg kg-1, respectively. |
Revisão Unified chromatography Mühlen, Carin von Lanças, Fernando Mauro Abstract in English: The scope of this study encompasses an overview of the principles of unified chromatography as well as the principles of chromatographic techniques as applied to unified systems, which include gas chromatography, liquid chromatography, supercritical fluid chromatography, high temperature and high pressure liquid chromatography, micro-liquid chromatography, enhanced fluidity chromatography, and solvating gas chromatography. Theoretical considerations and individual instrumental parameters such as mobile phase, sample introduction system, columns, and detection system are also discussed. Future applications of this separation approach are discussed. |
Revisão Polymer resins for lead separation and preconcentration Teixeira, Viviane G. Coutinho, Fernanda M. B. Gomes, Ailton S. Abstract in English: This article gives an overview of polymer materials used for lead separation and preconcentration. Different kinds of polymer resins, commercial or not, are cited as well as the most used functional groups attached to polymer backbones. The synthesis of these resins and conditions of lead adsorption and elution are remarked. The influence of the porous structure of the polymer on the resines performance is described as well as the use of spacer arms. |
Revisão Total mercury distribution as a proxy of urban and industrial pollition along the brazilian coast Marins, Rozane V. Paula Filho, Francisco José de Maia, Saulo Robério Rodrigues Lacerda, Luiz Drude de Marques, Wanessa Sousa Abstract in English: The monitoring of the pollution status of the Brazilian coast is hampered by the lack of a consistent environmental indicator. We propose Hg as an environmental proxy to anthropogenic pollution of coastal regions due to its absence in the Brazilian geology, its ubiquity in anthropogenic effluents, and its toxicity. Available data suggest Hg "backgrounds" in coastal sediments of 1-10 ng g-1, in the East and 15-30 ng g-1 in the South. We suggest short sediment cores to establish these values estimating a geo-accumulation index to compare all areas. The distribution of index values showed the majority of southern coast at least moderately contaminated whereas many eastern areas are still pristine. |
Revisão Validation for chromatographic and electrophoretic methods Ribani, Marcelo Bottoli, Carla Beatriz Grespan Collins, Carol H. Jardim, Isabel Cristina Sales Fontes Melo, Lúcio Flávio Costa Abstract in English: The validation of an analytical method is fundamental to implementing a quality control system in any analytical laboratory. As the separation techniques, GC, HPLC and CE, are often the principal tools used in such determinations, procedure validation is a necessity. The objective of this review is to describe the main aspects of validation in chromatographic and electrophoretic analysis, showing, in a general way, the similarities and differences between the guidelines established by the different Brazilian and international regulatory agencies. |
Revisão Chemical and enzymatic peptide syntheses: basic aspects and applications Machado, Alessandra Liria, Cleber W. Proti, Patrícia B. Remuzgo, César Miranda, M. Terêsa M. Abstract in English: This review begins with a brief discussion of the biological importance and chemical features of peptides. A description of the existing synthetic methods follows with emphasis on the basic aspects of the chemical and enzymatic syntheses. Techniques used to purify and characterize the synthesized peptides are also discussed. Finally, a few applications of the final products in chemistry, biochemistry, immunology and medicine are presented, such as identification and quantification of naturally occurring peptides, inspection of structure-activity relationships, therapeutics, development and/or improvement of analytical techniques and search for new vaccines. |
Revisão Square wave voltammetry. Second part: applications Souza, Djenaine de Codognoto, Lúcia Malagutti, Andréa R. Toledo, Renata A. Pedrosa, Valber A. Oliveira, Robson T. S. Mazo, Luiz H. Avaca, Luis A. Machado, Sergio A. S. Abstract in English: The aim of this work is to discuss some selected applications of square wave voltammetry published in the last five years. The applications focused here cover several electroanalytical fields such as: determination of pesticides; molecules with biological activity; metals and other environmental pollutants. Special attention is given to the work developed in the Grupo de Materiais Eletroquímicos e Métodos Eletroanalíticos - IQSC - USP concerning the utilization of square wave voltammetry, with different kinds of electrodes, for the determination of pesticides in natural waters and active principles in pharmaceutical formulations. The new methodology is simple, fast and sensitive when compared with the traditional ones such as chromatography and spectrophotometry. The satisfactory results obtained provide alternative procedures for the quality control of drugs and the monitoring of pesticides in natural environments. |
Revisão Polymer based nanocomposites: synthetic strategies for hybrid materials Esteves, Ana Catarina C. Barros-Timmons, Ana Trindade, Tito Abstract in English: Associating the well known advantages of hybrid materials to the wide potential of nanomaterials, the new and featuring class of polymer nanocomposites turned into one of the most intensively researched areas. This review highlights recent developments in the field of the synthesis of polymer based nanocomposites. Important issues related to the surface modification of fillers, in order to promote the compatibility between the inorganic/organic components, are also reported. The enhancement of the physical properties and the potential applications of polymer nanocomposites are considered in typical examples, given for each synthetic method described. |
Divulgação Strategies to increase sensitivity in UV-VIS spectrophotometry Rocha, Fábio R. P. Teixeira, Leonardo S. G. Abstract in English: Spectrophotometry is one of the most widespread analytical techniques due to its simplicity, reliability, and low-cost instrumentation for both direct measurements and coupled to other techniques or processes such as chromatography, electrophoresis and flow analysis. However, the application is often limited by sensitivity. This article describes some advances that greatly improve the performance of spectrophotometric measurements, especially in order to increase sensitivity, including the employment of liquid-core waveguides and solid-phase spectrophotometry. |
Divulgação The supporting electrolyte and its multiple functions on electrode processes Agostinho, Silvia M. L. Villamil, Ruth F. V. Agostinho Neto, Augusto Aranha, Hernani Abstract in English: The aim of this work is to present the principal properties and applications of supporting electrolytes (SE) to students, teachers and researchers interested in electrode processes. Different aspects are discussed including the importance of SE in maintaining constant the activity coefficients and the diffusion coefficients and reducing the transport number of electroactive species. Its effect on the electrochemical kinetic parameters is also presented. |
Divulgação Wastewater treatment by oxidation with ozone Almeida, Edna Assalin, Márcia Regina Rosa, Maria Aparecida Durán, Nelson Abstract in English: A large variety of organic and inorganic compounds may be found in wastewater which can contribute to environmental contamination. Oxidation processes with ozone (O3; O3/UV; O3/H2O2; O3/TiO2; O3/Mn+2) and the use of ozone in the pre- or post-treatment of wastewater combined with biological processes has been extensively studied for the treatment of effluents. The aim of this work was to evaluate the potential of the ozonation process in the treatment of several industrial wastewaters, namely effluents from paper mills, and textile, whey (dairy industry), pharmaceutic sand pesticides plants. |
Nota técnica A lab-made interface for acquisition of instrumental analog signals at the parallel port of a microcomputer Gaião, Edvaldo da Nóbrega Medeiros, Everaldo Paulo de Lyra, Wellington da Silva Moreira, Pablo Nogueira Teles Silva, Edvan Cirino da Araújo, Mário César Ugulino de Abstract in English: A lab-made interface for acquisition of instrumental analog signals between 0 and 5 V at a frequency up to 670 kHz at the parallel port of a microcomputer is described. Since it uses few and small components, it was built into the connector of a printer parallel cable. Its performance was evaluated by monitoring the signals of four different instruments and similar analytical curves were obtained with the interface and from readings from the instrument' displays. Because the components are cheap (~U$35,00) and easy to get, the proposed interface is a simple and economical alternative for data acquisition in small laboratories for routine work, research and teaching. |
Micro-scale zinc determination in a specific medicine Díaz, Oscar A. Alvarez, Elida Abstract in English: This work presents zinc determination in certain medicines that contain zinc oxide and zinc undecylenate. The technique consists of a spectrophotometric micro-scale titration, where EDTA is used as titrant, and xylenol orange as an indicator, in a medium adjusted to pH = 6 with acetic acid and sodium acetate. After each added portion of EDTA, the absorbance value is measured at a selected wavelength, in order to detect the end-point of the spectrophotometric titration. The results already obtained are satisfactory and promote student's interest. An additional contribution intends to propose the use of micro-scale techniques. |
Educação Simple flame photometric experiments to teach principles of atomic spectrometry in undergraduate analytical chemistry courses Okumura, Fabiano Cavalheiro, Éder T. G. Nóbrega, Joaquim A. Abstract in English: The purpose of this paper is the development of simple strategies to teach basic concepts of atomic spectrometry. Metals present in samples found in the daily lives of students are determined by flame atomic emission spectrometry (FAES). FAES is an accurate, precise, and inexpensive analytical method often used for determining sodium, potassium, lithium, and calcium. Historical aspects and their contextualization for students are also presented and experiments with samples that do not require pre-treatment are described. |
Assuntos gerais The evolution of commercial chemicals via their labels and containers Afonso, Júlio Carlos Aguiar, Renata de Melo Abstract in English: This work presents an evolution profile of labels and containers of commercial chemicals employed in laboratories since 1870. Most chemicals were made in Germany before the Second World War, after which many other manufacturers arrived on the Brazilian market. North-american products were dominant in the 1940s, but Brazilian chemicals have increased their participation along time. Labels presented increasingly more information, from originally simple names of the compounds at the beginning of the XXth century to the data presented today such as chemical formulae, safety regards and detailed chemical analysis. The raw material for container manufacturing also changed: glass was dominant until the 1950s, but nowadays plastic flasks are preferred whenever possible. Cork covers were replaced by screw caps. The diversity of commercial products also sharply increased with time, especially after the 1950s, following the many new and specific applications of chemicals for research and commercial purposes. |