Ionic silsesquioxane film immobilized on silica applied in the development of carbon paste electrode for determination of methyl parathion

A mesoporous silica-based hybrid material composed of silica xerogel modified with an ionic silsesquioxane, which contains the 1,4-diazoniabicyclo[2.2.2]octane chloride group, was obtained. The silsesquioxane film is highly dispersed on the surface. This hybrid material was utilized to develop a carbon paste electrode (CPE) for determination of methyl parathion. Transmission FTIR, elemental analysis and N₂ adsorption–desorption isotherms were used for characterization of the material. The electrochemical behavior of methyl parathion was evaluated by cyclic voltammetry and differential pulse voltammetry. It was observed a linear response to methyl parathion in the concentration range from 1.25 × 10^?7 to 2.56 × 10^?6 mol L^?1 by employing the carbon paste electrode, in Britton–Robinson buffer solution (pH 6). The achieved detection limit (3 SD of the blank divided by the slope of calibration curve) was 0.013 µmol L^?1 and sensitivity was 6.3 µA µmol L^?1. This result shows the potentiality of this electrode for application as electrochemical sensor for methyl parathion.     

Detection of carbamic and organophosphorous pesticides in water samples using a cholinesterase biosensor based on Prussian Blue-modified screen-printed electrode

In the present paper, a comparative study using Co-phthalocyanine and Prussian Blue-modified screen-printed electrodes, has been performed. Both the electrodes have demonstrated an easiness of preparation together with high sensitivity towards thicoholine (LOD = 5 × 10⁻⁷ and 5 × 10⁻⁶ M for Co-phthalocyanine and Prussian Blue, respectively) with high potentialities for pesticide measurement. Prussian Blue-modified screen-printed electrodes were then selected for successive enzyme immobilization due to their higher operative stability demonstrated in previous works. AChE and BChE enzymes were used and inhibition effect of different pesticides was studied with both the enzymes. AChE-based biosensors have demonstrated a higher sensitivity towards aldicarb (50% inhibition with 50 ppb) and carbaryl (50% inhibition with 85 ppb) while BChE biosensors have shown a higher affinity towards paraoxon (50% inhibition with 4 ppb) and chlorpyrifos-methyl oxon (50% inhibition with 1 ppb). Real samples were also tested in order to evaluate the matrix effect and recovery values comprised between 79 and 123% were obtained.     

In situ application of a cellulose bag and an ion exchanger for differentiation of labile and inert metal species in aquatic systems

This work involved the development and application of a new analytical procedure for in-situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory. The in-situ application involved immersing the DM-Cell-PAB system in two different rivers, enabling us to study the relative lability of metal species (Cu, Cd, Fe, Mn, and Ni) as a function of time and quantity of exchanger. The procedure is simple and opens up a new perspective for understanding environmental phenomena relating to the complexation, transport, stability, and lability of metal species in aquatic systems rich in organic matter.     

Behavior of Wild-type and Transfected S2 Cells Cultured in Two Different Media

An animal protein-free medium composed of IPL-41 containing 6 g L^?1 yeastolate ultrafiltrate, 10 g L^?1 glucose, 2 g L^?1 lactose, 5 g L^?1 glutamine, 1% lipid emulsion, and 0.1% Pluronic F-68 was used for producing recombinant proteins in batch mode employing two cell lines, S2AcRVGP2k expressing the G glycoprotein from rabies virus (RVGP) and S2AcHBsAgHy-9C expressing the surface antigen of hepatitis B virus (HBsAg), both obtained from Drosophila melanogaster S2 cells. Growth of wild-type S2 cells was also evaluated in the same medium. Cell behavior in the tested medium was compared to that verified in Sf900 II®. The results show that in shake flasks, S2AcRVGP2k and S2AcHBsAgHy-9C cells reached around 2?×?10⁷ cells mL^?1 in both media. In supplemented IPL-41 and Sf900 II® media, S2AcRVGP2k cells produced 367 ng RVGP mL^?1 and 638 ng RVGP mL^?1, respectively, while S2AcHBsAgHy-9C cells correspondently produced 573 ng HBsAg mL^?1 and 322 ng HBsAg mL^?1 in the mentioned media. In stirred tanks, S2AcRVGP2k cells reached 3?×?10⁷ cells mL^?1 and produced up to 758 ng RVGP mL^?1. In general, glucose was consumed by cells, while lactate and ammonia were produced.     

Assessment of trace metals contamination in estuarine sediments using a sequential extraction technique and principal component analysis

Fractionation of the metals Cd, Cr, Cu, Ni, Pb and Zn in sediments was performed for samples collected from eight locations in the Poxim river estuary of Sergipe State, northeast Brazil, using the 3-stage sequential extraction procedure proposed by the European Community Bureau of Reference (BCR). The extraction method was found to be satisfactory for analysis of certified reference material BCR-701, with recovery values ranging from 85% (Cu) to 117% (Cr). The detection limits obtained were 0.001 to 0.305 µg g^− 1. Zn exhibited greatest mobility and bioavailability, indicative of anthropogenic sources, while Cr was mainly found in the residual fraction and could be used as an indicator for the contribution from natural sources. Cd, Cu, Ni and Pb were associated with the oxidizable fraction, and Pb, Cr and Ni with the reducible fraction. Principal component analysis (PCA) clearly separated the metals into three groups: I (Zn); II (Pb); III (Cd, Cu, Cr and Ni). These groupings were mainly due to different distributions of the metals in the various fractions, in sediments from the different locations. Risk assessment code (RAC) analysis indicated that although the metals presented a moderate overall risk to the aquatic environment, nickel showed a low risk (RAC < 10%) at three sites, while zinc presented a high risk (RAC > 30%) at four other sites.     

PMMA-AES Blends Prepared by in situ Polymerization

Blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-g-(ethylene-co-propylene-co-diene)-g-styrene) (AES) were prepared by in situ polymerization. AES, a commercial elastomer obtained by radical copolymerization of styrene and acrylonitrile in the presence of ethylene-propylene-diene terpolymer (EPDM), was dissolved in methyl methacrylate and the in situ polymerization was conducted at 60 °C. The blends were characterized by CHN analysis, infrared spectroscopy (FTIR), carbon-13 nuclear magnetic resonance (¹³C NMR), dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM). These blends are immiscible and present complex phase behavior. Selective extraction of the blends’ components showed that a fraction of the material is crosslinked and grafting reactions on EPDM chains take place during MMA polymerization. Syndiotactic PMMA was obtained in the presence of AES and this syndiotactic-specificity increased with increasing amount of AES. The morphology of polymerized specimens showed irregular domains of elastomeric phase and in some cases inclusions of PMMA could be observed.     

Analytical tools for urocanic acid determination in human samples: A review

Urocanic acid is a chromophore found in the skin that has been identified as an important immunosuppressant and carcinogenesis mediator through its photoisomerization from trans to cis form induced by ultraviolet radiation. Research on analytical methods that explore urocanic acid isomerization is indispensable to fully understand the deleterious effects mediated by this biomarker. In this context, the current relevant analytical methods for determination of these isomers in human samples are summarized in this review. The methods presented here are applicable to human samples collected by noninvasive methods (or minimally invasive), encompassing an array of analytical techniques, including high‐performance capillary electrophoresis, confocal Raman spectroscopy, gas chromatography, high‐performance liquid chromatography, and mass spectrometry, among others. Developed high‐performance liquid chromatography methods have proven to be advantageous, allowing noninvasive collections for in vivo analysis and the confocal Raman, specially, for real‐time analysis. Among all these methods, high‐performance liquid chromatography is the most investigated one with mass spectrometry or ultraviolet detector, and the mass spectrometry detector being the most studied in the last years, demonstrating high sensitivity, very low detection limits, and accurate identification, especially for clinical investigations.     

Reduction of polycyclic aromatic hydrocarbons promoted by cobalt or manganese nanoparticles

A new methodology for the partial reduction of polycyclic aromatic and heteroaromatic hydrocarbons under mild reaction conditions is presented, the process being a reasonable alternative to the catalytic hydrogenation or the Birch reaction. The reduction protocol described is based on the use of cobalt or manganese nanoparticles generated in situ in a simple and economic way, by reduction of commercially available CoCl₂·6H₂O or MnCl₂·2H₂O in the presence of lithium sand and the corresponding PAH, acting itself as an electron carrier. The use of a deuterium-oxide-containing cobalt(II) salt allows the simple preparation of deuterium labeled products. The regiochemistry and degree of reduction in the case of 1-substituted naphthalene derivatives markedly depends on the nature of the metal-NPs used.     

Distillation of fermented sugarcane juice: fractions characterized by electrospray ionization mass spectrometry and multivariate data treatment

Direct infusion electrospray ionization mass spectrometry in the negative ion mode (ESI(?)‐MS) was employed to discriminate among fractions arising from the distillation of fermented sugarcane juice during the production of cachaça, a typical Brazilian alcoholic beverage. Aliquots were collected in the course of distillation and their ESI(?)‐MS shown to be almost indistinguishable by a simple visual inspection. However, when the ESI(?)‐MS data were treated by the principal component analysis (PCA) and hierarchical clustering analysis (HCA) statistical methods, four major groups were clearly determined, the so‐called head (two distinct clusters), heart and tail fractions. Furthermore, the recognition of diagnostic ions (and their respective intensities) enabled a more confident establishment of the cutoff position (i.e. the initial and final points of each fraction). In conclusion, ESI‐MS, in conjunction with PCA or HCA approaches, proved to be a quite efficient method that allowed for a prompt characterization of each fraction derived from the distillation of brewed sugarcane. The results described herein can, therefore, be useful not only to optimize the production of cachaça but also to improve the quality of the final product. Copyright © 2012 John Wiley & Sons, Ltd.