Novidades do acervo

terça-feira, 27. Março 2012

 

A ABC, por meio do CEDOPEM (Centro de Documentação Pesquisa e Memória), está sempre preocupada em manter seu acervo atualizado com artigos técnicos, livros e periódicos do Brasil e do exterior. Confira abaixo o conteúdo das novidades do acervo desta semana, Os textos estão somente em  inglês e disponíveis na integra exclusivamente para associados ABC. Faça já sua consulta gratuita pelo e-mail
 
 
Concentration of Cu(II) and Cd(II) from natural river water by adsorption on a modified silica surfasse
 
Guilherme Ferreira
 
A high surface area silica gel (737 ± m2 g-1) was synthesized modified through a two-step reaction with a 4-amino-2-mercaptopyrimidine ligand and applied to Cu(II) and Cd(II) adsorption from an aqueous medium. The modified material was characterized by FTIR, which showed that attachment of the molecule occurred via thiol groups at 2547 and 2600 cm-1, and by elemental analysis that indicated the presence of 0.0102 mmol of ligand. The data from adsorption experiments were adjusted to a modified Langmuir equation and the maximum adsorption capacity was 6.6 and 3.8 ìmol g-1 for Cu(II) and Cd(II), respectively. After adjusting several parameters, the material was applied in the preconcentration of natural river water using a continuous flow system before and after sample mineralization, and the results showed a 10-fold enrichment factor. The proposed method was validated through preconcentration and analysis of certified standard reference material (1643e), whose results were in agreement with the values provided by the manufacturer.
 
BrJac: Brazilian journal of analytical chemistry, Vol. 01, Nº 04, 175-180, 2011.
 
 
Association of Zn, Cd and As with proteins in Pityrogramma calomelanos and Nephrolepis biserrata submitted to oxidative and hydric stress
 
Luana Bacellar Melendez
 
This work represents a study of the association of zinc, cadmium and arsenic to proteins in terrestrial plants. Two plants species (Pityrogramma calomelanos and Nephrolepis biserrata) were collected at a site highly contaminated with to Cd, Zn and As, located in Sepetiba Bay, RJ-Brazil. Plant samples were dried at room temperature and crushed. Then plant proteins were extracted. The fractions were immediately injected into an hyphenated system SEC-UV-ICP-MS, using a Superdex 200 10/300 GL column. The results showed an association of zinc, cadmium and arsenic to three proteins with molar mass ranges of 94.7 ± 0.2 kDa (present in P. calomelanos); of 31.6 ± 2.6 kDa and of 20.2 ± 0.6 kDa (in both plant species). Moreover, the results also showed that zinc, cadmium and arsenic are preferentially associated to a protein whose molar mass is close to superoxide dismutase - SOD (32 kDa), normally associated with oxidative stress processes. In both species the arsenic also shows association to a protein whose molar mass is close to that of dehydrins (19 and 24 kDa), which are produced by plants under conditions of high salinity in dry environments.
 
BrJac: Brazilian journal of analytical chemistry, Vol. 01, Nº 04, 181-186, 2011.
 

Potentiality of the use of montmorillonite in diffusive gradients in thin film (DGT) devices for determination of labile species of Cu, Cr, Cd, Mn, Ni, Pb, and Zn in natural Waters
 
Vanessa Egea dos Anjos
 
Diffusive gradients in thin films (DGT) were used for characterization of the lability of metallic species in synthetic natural waters. We investigated the possibility of using an alternative low cost binding phase based on montmorillonite (MT) in DGT devices to determine labile fractions of Cu2+, Cr3+, Cd2+, Mn2+, Ni2+, Pb2+, and Zn2+ in natural waters. Evaluation of the applicability of montmorillonite for use in DGT devices was performed for metallic species under similar conditions to those found in freshwaters. The percentage of sorption and desorption obtained ranged from 78 ± 5% to 100 ± 2% for the elements studied, indicating that MT exhibited excellent sorption and desorption properties for all elements. DGT devices with montmorillonite were evaluated by recovery tests, with results ranging from 91 ± 6% to 103 ± 6%, being considered satisfactory. The lability of elements in model systems was comparatively evaluated using conventional DGT and MT-DGT devices. Both devices remained between 24 and 72 h in synthetic freshwater samples. The results obtained with both conventional and modified DGT devices showed no statistically significant differences, with 95% confidence. The labile fraction of elements decreased with time, indicating that kinetics is a relevant factor to be considered in studies of speciation. It can be concluded that the MT-DGT devices can be used satisfactorily in determination of labile species of various elements in natural waters.
 
BrJac: Brazilian journal of analytical chemistry, Vol. 01, Nº 04, 187-193, 2011.
 

Chromium speciation in waters using silica nanoparticles organofunctionalized with APTES and graphite furnace atomic absorption spectrometry
 
Maciel Luz
 
A method for the Cr(VI) speciation in waters using silica nanoparticles organofunctionalized with (3-aminopropyl)triethoxysilane (APTES) and graphite furnace atomic absorption spectrometry is proposed. The best conditions for analysis were using 150 mg of silica nanoparticles organofunctionalized with 2.0% (v v-1) of APTES and pH~8. For the heating program the pyrolysis and atomization temperatures were fixed at 1400 oC and 2400 oC, respectively, 10 ìg Mg were used as chemical modifier. The detection limits (n=10, 3ó) were 0.06 ìg L-1 for total Cr and Cr(VI) determinations. The reliability of the proposed method was checked by addition and recovery of Cr(VI) and the results showed recoveries between 91 and 105%.
 
BrJac: Brazilian journal of analytical chemistry, Vol. 01, Nº 04, 194-200, 2011.
 
 
The feasibility of coupling graphite furnace with solid phasese microextraction aiming at speciating organotin compounds
 
Aline Soriano Lopes
 
The goal of this work was to perform the coupling between solid phase microextraction using a SPME fiber device and graphite furnace atomic absorption spectrometry for extracting organotin compounds volatilized during the drying step of the graphite furnace temperature program. In this way, evaluations of volatilization temperatures, ranging from 60 to 120oC, and fiber exposure times (190, 390, 590, 790 and 990 s) were carried out for optimizing the separation of DBT and TBT from sediment matrices. In order to identify the species extracted using the graphite furnace, GC-MS was used. Additionally, a separation/retention model was proposed regarding the DBT and TBT species on the SPME fiber inserted into the graphite furnace
 
BrJac: Brazilian journal of analytical chemistry, Vol. 01, Nº 04, 201-205, 2011.
 
 
Metallothioneins and metallothionein-like proteins as biomarkers of environmental contamination: techniques for extraction, separation and quantification - a review
 
Rodrigo Cunha Wanick
 
Even after fifteen years of studies of metallothioneins (MTs) and metallothionein-like proteins (MTLPs) as biomarkers of trace metal exposure, the methods for extraction, separation and detection of these proteins are still without an appropriate standardization, which has generated questions about the effectiveness of these methods. This review describes available methods of extraction, separation and detection for these proteins that have been applied with marine invertebrates used in biomonitoring of trace metal contamination in the environment. Extraction procedures using heat treatments seem more appropriate due to lower loss of MTs and MTLPs during the pre-treatment step when compared with solvent precipitation. As for MTs and MTLPs separation, electrophoretic and chromatographic methods have proven to be convenient techniques as these allow determination and speciation of trace metals associated with these proteins and also allow their identification by mass spectrometry. Nevertheless, after a characterization of these proteins in a selected biological matrix, indirect methods for MT and MTLP determination could be applied because these are relatively simple and less expensive, ideal for routine analysis as is demanded for biomonitoring studies.
 
BrJac: Brazilian journal of analytical chemistry, Vol. 01, Nº 04, 206-221, 2011.
 
 
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