Dependence of the electrical conductivity and elastomeric properties on sample preparation of blends of polyaniline and natural rubber

Blend films (free-standing) containing 20% in volume of polyaniline (PANI) in 80% of natural rubber (NR) were fabricated by casting in three different ways: (1) adding PANI-EB (emeraldine base) dissolved in N-methyl-2-pyrrolidone (NMP) to the latex (NRL), (2) adding PANI-EB dissolved in in-cresol to NR dissolved in xylol (NRD), (3) overlaying the surface of a pure NR cast film with a PANI layer grown by in situ polymerization (NRO). All the films were immersed into HCl solution to achieve the primary doping (protonation) of PANI before the characterization. The main goal here was to investigate the elastomeric and electrical conductivity properties for each blend, which may be applied as pressure and deformation sensors in the future. The characterization was carried out by optical microscopy, dc conductivity, vibrational spectroscopy (infrared absorption and Raman scattering), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile stress-strain curves. The results suggest that the NRL blend is the most suitable in terms of mechanical and electrical properties required for applications in pressure and deformation sensors: a gain of conductivity without losing the elastomeric property of the rubber. (c) 2005 Wiley Periodicals, Inc.

Determination of macro- and micronutrients in plant leaves by high-resolution continuum source flame atomic absorption spectrometry combining instrumental and sample preparation strategies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Phosphite determination in fertilizers after online sequential sample preparation in a flow injection system

A flow injection spectrophotometric system is proposed for phosphite determination in fertilizers by the molybdenum blue method after the processing of each sample two times on-line without and with an oxidizing step. The flow system was designed to add sulfuric acid or permanganate solutions alternately into the system by simply displacing the injector-commutator from one resting position to another, allowing the determination of phosphate and total phosphate, respectively. The concentration of phosphite is obtained then by difference between the two measurents. The influence of flow rates, sample volume, and dimension of flow line connecting the injector-commutator to the main analytical channel was evaluated. The proposed method was applied to phosphite determination in commercial liquid fertilizers. Results obtained with the proposed FIA system were not statistically different from those obtained by titrimetry at the 95% confidence level. In addition, recoveries within 94 and 100% of spiked fertilizers were found. The relative standard deviation (n = 12) related to the phosphite-converted-phosphate peak alone was <= 3.5% for 800 mg L-1 P (phoshite) solution. Precision due to the differences of total phosphate and phosphate was 1.1% for 10 mg L-1 P (phosphate) + 3000 mg L-1 P (phosphite) solution. The sampling rate was calculated as 15 determinations per hour, and the reagent consumption was about 6.3 mg of KMnO4, 200 mg of (NH4)(6)Mo7O24 center dot 4H(2)O, and 40 mg of ascorbic acid per measurement.

Spectrophotometric determination of phosphite in fertilizers in a flow injection system with online sample preparation

A flow injection system with online sample preparation is proposed for the determination of phosphite in liquid fertilizers by spectrophotometry. After loop-based injection, phosphite is oxidized by an acidic permanganate solution (1.0 10(-2) mol L-1 KMnO4 + 1.0 mol L-1 H2SO4) in a heated reactor (50 degreesC). The phosphate generated is then determined by the molybdenum blue method. Influence of flow rates, temperature, and concentration and order of addition of reagents, sample volume, and reactor configuration for the blue complex formation on recorded signals were investigated. The pow system was applied to phosphite determination in commercial samples of liquid fertilizers. The proposed system handles about 80 samples per hour [0.05-0.40% (w/v) H3PO3; R = 0,9998], consuming about 80 muL sample, 1 mg KMnO4, 25 mg (NH)(6)Mo7O24, and Ia mg ascorbic acid per determination. Results are precise [relative standard deviation less than or equal to 3.5% for 0.1% (w/v) H3PO3, n = 12] and in agreement with those obtained by gravimetry at 95% confidence level. (C) 2000 John Wiley & Sons, Inc.

Evaluation of sample preparation procedures and krypton as an interference standard probe for arsenic speciation by HPLC-ICP-QMS

Different conditions of extraction using water, a methanol-water mixture and nitric acid solutions were evaluated for speciation of As(iii), As(v), DMA and MMA in plant samples that previously received As(v) after being sown and emergence was investigated. Microwave-assisted extraction (MAE) using diluted nitric acid solutions was also performed for arsenic extraction from chicken feed samples. The separation and determination of arsenic species were performed using HPLC-ICP-MS. The interference standard method (IFS) using 83Kr+ as the IFS probe was employed to minimize spectral interferences caused by polyatomic species, such as 40Ar 35Cl+. The extraction procedures tested presented adequate extraction efficiencies (90%), and the four arsenic species evaluated were found in plant samples. Extractions with diluted nitric acid solution at 90 °C were the most efficient strategy, with quantitative recoveries for all four As species in plant tissues. On the other hand, the methanol-water mixture was the solvent with the lowest extraction efficiency (50-60%). For chicken feed samples, MAE at 100 °C for 30 min resulted in an extraction efficiency of 97% and only As(v) was found, without any species interconversion. The IFS method contributed to improving precision and limits of detection and quantification for all tested extraction procedures. Significant improvements on accuracy were obtained by applying the IFS method and recoveries between 77 and 94%, and 82 and 93% were obtained for plant extracts and chicken feed samples, respectively. This journal is © 2013 The Royal Society of Chemistry.

Optimisation of a sample preparation method for the determination of fumonisin B-1 in rice

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparative clinical sample preparation of DNA and RNA viral nucleic acids for a commercial deep sequencing system (Illumina MiSeq (R))

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fecal specimens preparation methods for PCR diagnosis of human taeniosis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative procedures for the sample decomposition of rocks used in organic agriculture and the determination of Cu, Fe, Mn, and Zn by FAAS

The aim of this work was to develop an appropriate sample preparation procedure for the flame atomic absorption spectrometry determination of Cu, Fe, Mn, and, Zn in rocks used in organic agriculture as a source of macro- and micronutrients.Six different procedures were evaluated and are classified into three groups: (a) pressure digestion system with Teflon bombs, (b) conventional wet digestion in a digester heating block, and (c) closed microwave system with pressure and temperature control.Two standard reference materials and two commercial samples were analyzed. It was found that the closed microwave system required low reagent consumption, less time, and resulted in low contamination.

Comparative studies of the sample decomposition of green and roasted coffee for determination of nutrients and data exploratory analysis

The contents of some nutrients in 35 Brazilian green and roasted coffee samples were determined by flame atomic absorption spectrometry (Ca, Mg, Fe, Cu, Mn, and Zn), flame atomic emission photometry (Na and K) and Kjeldahl (N) after preparing the samples by wet digestion procedures using i) a digester heating block and ii) a conventional microwave oven system with pressure and temperature control. The accuracy of the procedures was checked using three standard reference materials (National Institute of Standards and Technology, SRM 1573a Tomato Leaves, SRM 1547 Peach Leaves, SRM 1570a Trace Elements in Spinach). Analysis of data after application of t-test showed that results obtained by microwave-assisted digestion were more accurate than those obtained by block digester at 95% confidence level. Additionally to better accuracy, other favorable characteristics found were lower analytical blanks, lower reagent consumption, and shorter digestion time. Exploratory analysis of results using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that Na, K, Ca, Cu, Mg, and Fe were the principal elements to discriminate between green and roasted coffee samples. ©2007 Sociedade Brasileira de Química.

Study of interstitial oxygen mobility in RuSr2GdCu2O8 by internal friction

The discovery of the spatial uniform coexistence of superconductivity and ferromagnetism in ruthenocuprates, RuSr2GdCu2O8 (Ru-1212), has spurred an extraordinary development in the study of the competition between magnetism and superconductivity. However, several points of their preparation process and characterization that determine their superconductive behaviour are still obscure. The improvement of sample preparation conditions involves some thermal treatments in inert atmosphere. Anelastic spectroscopy measurements were made using an inverted torsion pendulum, operating with an oscillation frequency of 38 Hz, temperature in the 90 and 310 K range, heating rate of 1 K/min, and vacuum better than 10(-3) Pa. The results show anelastic relaxation peaks at 210 K related to the presence of interstitial oxygen atoms. The peaks decrease significantly with the oxygen loss caused by the heat treatments in vacuum, appearing again after the annealing of the sample in an oxygen atmosphere. These observed peaks are clearly related to the additional oxygen atoms, with activation energy 0.13 and 0.36 eV, and can be explained in terms by diffusional jumps of interstitial oxygen in the RuO2 planes. (C) 2009 Elsevier B.V. All rights reserved.

Comparison of fracture surface and plane section analysis for ceramic grain size characterisation

A method has been developed to obtain quantitative information about grain size and shape from fractured surfaces of ceramic materials. One elaborated a routine to split intergranular and transgranular grains facets of ceramic fracture surfaces by digital image processing. A commercial ceramic (ALCOA A-16, Al2O3-1.5% of CrO) was used to test the proposed method. Microstructural measurements of grain shape and size taken from fracture surfaces have been compared through descriptive statistics of distributions, with the corresponding measurements from polished and etched surfaces. The agreement between results, with the expected bias on grain size values from fractures, obtained for both types of surfaces allowed to infer that this new technique can be used to extract the relevant microstructural information from fractured surfaces, thus minimising the time consuming steps of sample preparation. (C) 2003 Elsevier Ltd. All rights reserved.

The structure and optical dispersion of the refractive index of tellurite glass

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparison of the univariate and multivariate methods in the optimization of experimental conditions for determining Cu, Pb, Ni and Cd in biodiesel by GFAAS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development of a method to determine Ni and Cd in biodiesel by graphite furnace atomic absorption spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)