Rapid separation of post‐blast explosive residues on glass electrophoresis microchips

This study describes the development of an analytical methodology based on the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C⁴D) for the separation and detection of inorganic anions in post‐blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol/L lactic acid, 10 mmol/L histidine and 0.070 mmol/L cetyl(trimethyl ammonium) bromide. For C⁴D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 V_pp. The separation of Cl^?, NO₃^?, NO₂^?, SO₄^2?, ClO₄^? and ClO₃^? was performed within ca. 150 s with baseline resolution and efficiencies between 4.4 × 10⁴ and 1.7 × 10⁵ plates/m. The found limits of detection ranged between 2.5 and 9.5 μmol/L. Last, real samples of post‐blast explosive residues were analyzed on the ME‐C⁴D devices obtaining successfully the determination of Cl^?, NO₃^? and SO₄^2?. The achieved concentration values varied between 12.8–72.5 mg/L for Cl^?, 1.7–293.1 mg/L for NO₃^? and 1.3–201.3 mg/L for SO₄^2?. The data obtained using ME‐C⁴D devices were in good agreement with the concentrations found by ion chromatography. The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the ME‐C⁴D devices emerge as a powerful and portable analytical platform for on‐site analysis demonstrating to be a promising tool for the crime scene investigation.     

Influence of the PVOH molar mass on the morphology and functional properties of EVOH/PVOH films prepared by melt blending

The influences of the molar mass (low, medium, and high) and content of poly(vinyl alcohol) (PVOH) dispersed by melt-blending in an ethylene vinyl alcohol (EVOH) copolymer on the morphology, microstructure, thermal, mechanical, and oxygen barrier properties were investigated. Multilayer films with external low-density polyethylene layers and inner EVOH/PVOH blend layer and respective monolayer films were elaborated and characterized. EVOH/PVOH blends exhibited a good compatibility because of the initial presence of PVOH segments in EVOH. The detailed quantitative analysis of the morphology performed for all blends showed that the finest dispersion was obtained with the PVOH with the lowest molar mass. The properties of the films as a function of the PVOH content and its molar mass were determined herein. Significant improvement of barrier properties was obtained at moderated water activities (up to a_w = 0.6) by using the PVOH with the lowest molar mass. Compared to the neat EVOH material, the oxygen permeability coefficients decreased by a factor 2 by adding 15 vol% PVOH while the thermal and mechanical properties remained similar.     

Preparation and characterization of boron-based bioglass by sol−gel process

45S5 bioglass has been widely studied in the last few decades because of its bioactivity and promising applications in the biomedical field. Boron, even few studied, represents a potential element to improve the properties of the 45S5 bioglass derivatives. The bioglasses are conventionally prepared by heat treatment of oxides and silicon. Here, the sol?gel method is proposed for the preparation of the boron-based 45S5 bioglass (45S5B) and the classical 45S5 bioglass (45S5), using water-soluble salts as raw materials. The bioglasses were characterized by FTIR, XRD, and SEM, indicating the success of the sol?gel method for preparation of the samples. The bioglasses were also tested in vitro for bioactivity in biological conditions and cytotoxicity against eukaryotic cells. The bioactivity of 45S5B was similar to the bioactivity of 45S5 bioglass, indicated by the deposition of hydroxyapatite crystals at the surface of the pristine bioglasses. The results of cytotoxicity tests revealed that the IC₅₀ of 45S5B (IC₅₀?=?7.56?mg?mL^?1) was similar to the IC₅₀ of 45S5 (IC₅₀?=?8.15?mg?mL^?1), indicating its safety for application in the biomedical field.

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Silica nanoparticles at interfaces modulated by amphiphilic polymer and surfactant

The interfacial behavior of silica nanoparticles in the presence of an amphiphilic polymer poly( N-isopropylacrylamide) (PNIPAM) and an anionic surfactant sodium dodecyl sulfate (SDS) is studied using neutron reflectivity. While the nanoparticles do not show any attraction to hydrophilic and hydrophobic surfaces in pure water, presence of the amphiphilic polymer induces significant adsorption of the nanoparticles at the hydrophobic surface. This interfacial behavior is activated due to interaction of the nanoparticles with PNIPAM, the amphiphilic nature of which leads to strong adsorption at a hydrophobic surface but only weak interaction with a hydrophilic surface. The presence of SDS competes with nanoparticle-PNIPAM interaction and in turn modulates the interfacial properties of the nanoparticles. These adsorption results are discussed in relation to nanoparticle organization templated by dewetting of charged polymer solutions on a solid substrate. Our previous studies showed that nanoparticle assembly can be induced to form complex morphologies produced by dewetting of the polymer solutions, such as a polygonal network and long-chain structures. This approach, however, works on a hydrophilic substrate but not on a hydrophobic substrate. These observations can be explained in part by particle-substrate interactions revealed in the present study.     

A combination of statistical and analytical evaluation methods as a new optimization strategy for the quantification of pharmaceutical residues in sewage effluent

In this study, a new solid-phase microextraction (SPME) method for simultaneous extraction of pharmaceutical compounds with acidic and basic characteristics (ibuprofen, fenoprofen, diclofenac, diazepam and loratadine) from residual water samples is proposed. In this procedure, the extraction is processed using two distinct sample pH values. The extraction is begun at pH 2.5 to promote the sorption of acidic pharmaceuticals and after 35 min the sample pH is changed to 7.0 by adding 0.4 mol L⁻¹ disodium hydrogenphosphate, so that the basic compounds can be sorbed by the fiber (20 min). The pH change is performed without interruption of the extraction process. A comparison between the proposed method and the SPME method applied to each group of the target compounds was performed. Gas chromatography coupled to mass spectrometry was used for separation and detection of analytes. The extraction conditions for the three methods were optimized using full factorial experimental design, response surface through a Doehlert matrix and central composite design. Limits of detection (0.02-0.43 μg L⁻¹) and correlation coefficients (0.9970-0.9998) were determined for the three methods. The proposed extraction procedure was applied to samples of sewage treatment plant effluent and untreated wastewater. Recovery and relative standard deviation values ranged from 67 to 116% and 4.6 to 14.5%, respectively, for all compounds studied. Modification of sample pH during the extraction procedure was shown to be an excellent option for all of the compounds and may be extended to the simultaneous extraction of other compounds with different acid-base characteristics.     

Use of hydrogen peroxide to achieve interference-free stripping voltammetric determination of copper at the bismuth-film electrode

In this work, a new approach is presented to allow interference-free determination of Cu (II) by stripping voltammetry using the bismuth-film electrode. The addition of hydrogen peroxide to the electroanalytical cell has promoted complete resolution between re-dissolution peaks of Bi (III) and Cu (II). The absence of interference could be evaluated by the correlation coefficient (r > 0.99) between Cu (II) concentration and its shifted current peak (at +212 mV) while achieving a slightly fluctuation of the bismuth current peak at −180 mV. Studies were performed aiming towards the optimum conditions for trace determination of Cu (II) using hydrogen peroxide. The methodology was applied to a real sample (sugarcane spirits) and the results were compared to those from graphite furnace atomic absorption spectrometry. The analytical parameters of merit and the results of the analysis indicated that the analytical methodology could be readily used for trace determination of Cu (II).     

Reactive doping of PAni–CSA and its use in microwave absorbing materials

Conductive coatings have been studied for static dissipation and as microwave absorbing materials. The doping process of polyaniline (PAni), which makes it conductive, is an important stage that determines the coating performance. For this purpose, polyaniline was doped by reactive processing in a torque rheometer using different molar ratios between PAni and acid (PAni:CSA) at three different temperatures (80, 90, and 100°C). Aqueous solution doping was also used in the ratio of 1:2 of PAni/CSA, with the aim to investigate the influence of different methods of PAni doping on its characteristics and, consequently, on the performance of coatings. Thermal analyses of the processed materials showed that PAni doped by both routes, reactive and solution processing, showed similar behaviors. X‐ray diffraction analyses showed a semicrystalline structure for the PAni–CSA doped by reactive processing using high CSA concentrations and temperature. It was also observed that the doping process affects the dispersion of the components into the conductive coatings. Microwave absorption measurements (8–12 GHz) of PU‐doped PAni blends showed the dependence of the doping type, the PAni–CSA concentration, and the mixing conditions of the components on the coating performance; it was found up to 99% of attenuation of the incident radiation for some composites in a narrow frequency range. The microwave absorption efficiency of the coating samples prepared by using the reactive doping process indicates the advantage of this methodology over solution doping. Moreover, the reactive process addresses the environmental requirements. Copyright © 2008 John Wiley & Sons, Ltd.     

Efficiency and sustainability assessment for a group of farmers in the Brazilian Amazon

The aim of this paper is to use DEA models to evaluate sustainability in agriculture. Several variables are taken into account and the resulting efficiency is measured by comparison. The performance of family farms is analysed here (variables: farmed area, work force, and production). As agricultural sustainability depends on the maintenance of systems of production for long periods of time, the models were run for the years of 1986 and 2002. Tiered DEA models were used to group farmers in sustainability categories. Non-parametric regression models were used to identify the factors affecting the efficiency measurements. All the results indicate that the majority of the farmers increased their efficiency along the time. These improvements may support the existence of sustainability.     

Low-resolution 1H spin-spin relaxation of n-decane/water emulsions stabilized by beta-casein

A low-resolution ¹H NMR relaxometry study on the dynamics of an n-decane/water emulsion stabilized by β-casein is presented. Spin–spin (transverse) relaxation time constants (T₂) were used to assess relative mobilities of emulsion components, by a selective deuteration procedure. Data analysis allowed the emulsion investigated to be described by a heterogeneous collection of dynamically distinct populations. A major population of n-decane molecules presented an average mobility that very nearly approached that of pure solvent, which is compatible with its occurrence in the emulsion continuous microphase. β-Casein molecules displayed a prevalent population with significantly decreased mobility as compared to the free protein in solution, which is in accordance with the protein location at the oil/water interface. Also, a major H₂O population with significantly lower average T₂ as compared to the pure liquid was detected and has been assigned to interfacial water.