Magnetic properties of Fe−Mn−Al alloy system in the FCC disordered phase

In this work we report the experimental studies of Fe?Mn?Al alloys in the FCC disordered phase at room temperature by Mössbauer spectroscopy and X-ray diffraction. In this phase the alloys are antiferromagnetic with a constant mean hyperfine field ( \(\bar H\) ) near 26 kOe in the composition range from 0 to 7.5 at.% Al and 50 to 65 at.% Fe. When the Al or Fe concentration increases, the \(\bar H\) value gradually decreases to zero and the alloy becomes paramagnetic. In the same way when the Al concentration increases the lattice parameter increases linearly but when the Fe concentration increases the lattice parameter remains nearly constant for alloys with 5 at.% Al and decreases for alloys with 10 at.% Al.     

A simple and green analytical method for determination of glyphosate in commercial formulations and water by diffuse reflectance spectroscopy

This article describes a simple, inexpensive, and environmentally friendly method for the monitoring of glyphosate using diffuse reflectance spectroscopy. The proposed method is based on reflectance measurements of the colored compound produced from the spot test reaction between glyphosate and p-dimethylaminocinnamaldehyde (p-DAC) in acid medium, using a filter paper as solid support. Experimental designs were used to optimize the analytical conditions. All reflectance measurements were carried out at 495 nm. Under optimal conditions, the glyphosate calibration graphs obtained by plotting the optical density of the reflectance signal (AR) against the concentration were linear in the range 50-500 μg mL(-1), with a correlation coefficient of 0.9987. The limit of detection (LOD) for glyphosate was 7.28 μg mL(-1). The technique was successfully applied to the direct determination of glyphosate in commercial formulations, as well as in water samples (river water, pure water and mineral drinking water) after a previous clean-up or pre-concentration step. Recoveries were in the ranges 93.2-102.6% and 91.3-102.9% for the commercial formulations and water samples, respectively.     

Selective determination of copper with pyridoin phenylhydrazone as chromogenic extraction reagent

Summary The synthesis, characteristics and analytical applications of pyridoin phenylhydrazone are described. It reacts with copper(I) to produce an orange 11 complex ( _max=450 nm,=2.1×10⁴l· mole^–1·cm^–1) in aqueous ethanolic solution; it behaves as a cuproin type reagent. The orange complex can be extracted into amyl alcohol ( _max=440 nm,=2.0×10⁴l·mole^–1·cm^–1), and used for the spectrophotometric determination of trace amounts of copper. Interferences have been investigated.

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Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoin-phenylhydrazon wurden beschrieben. Es reagiert mit Cu(I) unter Bildung eines orange gefärbten 11-Komplexes in wäßrig-alkoholischer Lösung ( _max=450 nm,=2,1×10⁴l·mol^–1·cm^–1); das Reagens verhält sich ähnlich wie Cuproin. Der erwähnte Komplex läßt sich mit Amylalkohol extra-hieren ( _max=440 nm,=2,0×10⁴l·mol^–1·cm^–1) und zur spektrophoto-metrischen Bestimmung von Kupferspuren benützen. Auftretende Störungen wurden angegeben.

     

Transuranic elements alpha-particle energy analysis using nuclear track in solids methodology

This paper presents a method for the energy analysis of alpha-particles emitted by transuranic elements via a novel technique using Nuclear Tracks. The method is based on the relationship between the energy deposited in the detection material and the diameter of the track, that is formed by chemical etching. The method involves CR-39 polycarbonate as the detector material, one-step chemical etching after irradiation, and a digital image analysis system for automatic reading of the track diameters. The experimental study included alpha-particles in the energy range 5.1 MeV to 5.8 MeV emitted by²³⁹Pu,²⁴¹Am and²⁴⁴Cm. The quantitative results provide a clear signature to identify each one of the emitters based on a characteristic track diameter.     

Simple and sensitive determination of low-molecular-mass aromatic aldehydes in swimming pool water by LC-diode array detector

This work reports the development of a simple method for the quantitative determination of aromatic and aliphatic low-molecular-mass aldehydes (LMMAs) as disinfection by-products (DBPs) in indoor swimming pool waters after chlorination with a simplified SPE sample treatment. The method is based on the continuous in situ derivatization/preconcentration of the aldehydes with 2,4-dinitrophenylhydrazine (DNPH) on a Lichrolut EN column in the presence of β-CD. After elution, the 2,4-dinitrophenylhydrazine derivatives were separated on an RP-C(18) analytical column using gradient of ACN-water at 60-80%. The optimized sample treatment described here allowed the direct analysis of large volumes of water in order to improve the sensitivity of the method; LODs in the 60-120 ng/L range were achieved for aromatic LMMAs by using a volume of 50 mL of water, precision being 7.5% or better at a concentration level of 5 μg/L. These results indicate that the ensuing method is a useful choice for the determination of LMMAs in water samples that provides better results than reported LC alternatives in terms of the LOD (except for MS/MS detection), sample requirements for analysis and cost.     

Immobilization of Anti-Galectin-3 onto Polysiloxane–Polyvinyl Alcohol Disks for Tumor Prostatic Diseases Diagnosis

This work aimed to immobilize the antibody anti-galectin-3 onto polysiloxane–polyvinyl alcohol (POS-PVA) support, to evaluate its capacity to capture the serum antigen galectin-3 and to quantify by ELISA the antigen levels in sera from patients with prostatic adenocarcinoma (PA) and benign prostatic hyperplasia (BPH) and healthy individuals. Also, for comparative effect, the galectin-3 expression in the prostate tissue through immunohistochemistry was evaluated. The optical density (galectin-3 level) values established for the sera from PA and BPH patients were lower compared with those found for the healthy individuals. Galectin-3 immunohistochemically showed a significant increase and reduction of the cytoplasmatic protein expression in BPH and PA, respectively, compared with the normal prostate. These results showed that POS-PVA disks could be used as solid phase to immobilize serum galectins and in immunoassays procedures for the correspondent IgG anti-galectins detection in human sera.     

Unusual vesicle-micelle transitions in a salt-free catanionic surfactant: temperature and concentration effects

The spontaneous formation of vesicles by the salt-free surfactant hexadecyltrimethylammonium octylsulfonate (TASo) and the features of an unusual vesicle-micelle transition are investigated in this work. In a previous work, we have shown that this highly asymmetric catanionic surfactant displays a rare lamellar miscibility gap in the concentrated regime. Here, we analyze in detail the aggregation behavior in the dilute regime (less than 3 wt % surfactant) as a function of both concentration and temperature. The phase diagram is dominated by a two-phase region consisting of a dispersion of a swollen lamellar phase (Lalpha') in the excess solvent phase (L1). Stable vesicles form in this two-phase region, and upon temperature increase, a transition to a single solution phase containing only elongated micelles occurs. The structural characterization of the aggregates and the investigation of their equilibrium properties have been carried out by light microscopy, cryo-TEM, water self-diffusion NMR, and SANS. Similarly to the lamellar-lamellar coexistence, the changes in microstructure at high dilution and high temperature can be understood from solubility differences, electrostatic interactions, and preferred aggregate curvature. Surface charge in the aggregates stems from the higher solubility of the octylsulfonate (So-) ion as compared to that of the hexadecyltrimethylammonium ion (TA+). Upon temperature increase, the ratio of free So(-) relative to the neutral TASo increases. Consequently, the surface charge density of the aggregates increases, and this ultimately induces a transition to a higher-curvature morphology (elongated micelles). Vesicles can also be spontaneously formed by cooling solutions from the micellar region, and the mean size obtained is practically independent of cooling rate, suggesting that dissociation/charge effects also control this process.     

Thermodynamic study of 1,2,3-triphenylbenzene and 1,3,5-triphenylbenzene

The energetic study of 1,2,3-triphenylbenzene (1,2,3-TPhB) and 1,3,5-triphenylbenzene (1,3,5-TPhB) isomers was carried out by making use of the mini-bomb combustion calorimetry and Knudsen mass-loss effusion techniques. The mini-bomb combustion calorimetry technique was used to derive the standard (p° = 0.1 MPa) molar enthalpies of formation in the crystalline state from the measured standard molar energies of combustion for both isomers. The Knudsen mass-loss effusion technique was used to measure the dependence with the temperature of the vapour pressure of crystalline 1,2,3-TPhB, which allowed the derivation of the standard molar enthalpy of sublimation, by application of the Clausius–Clapeyron equation. The sublimation study of 1,3,5-TPhB had been performed previously. From the combination of data obtained by both techniques, the standard molar enthalpies of formation in the gaseous state, for both isomers, at T = 298.15 K, were calculated. The results indicate a higher stability of the 1,3,5-TPhB isomer relative to 1,2,3-TPhB, similarly to the terphenyls. Nevertheless, the 1,2,3-TPhB isomer is not as energetically destabilized as one might expect, supporting the existence of a π–π displacive stacking interaction between both pairs of outer phenyl rings. The volatility difference between the two isomers is ruled by the enthalpy of sublimation. The volatility of the 1,2,3-TPhB is two orders of magnitude higher than the 1,3,5-TPhB isomer, at T = 298.15 K.     

110.

Determination of lithium in pharmaceutical formulations used in the treatment of bipolar disorder by flow injection analysis with spectrophotometric detection     

Cássia Maria L. da Silva 《Talanta》2007,73(4):613-620

In this work, a flow injection system with spectrophotometric detection was developed for the determination of lithium in pharmaceutical formulations used in the treatment of bipolar disorder. Reaction between Quinizarine (1,4-dihydroxyanthraquinone) and Li(I) ion in alkaline medium containing dimethylsulfoxide (DMSO) was explored for this purpose. The flow system was optimized regarding to its chemical (DMSO, Quinizarine and NaOH concentrations and sample pH) and physical parameters (sample loop volume, carrier flow rate and reactor length) in order to establish better conditions in terms of sensitivity and sampling frequency. The results obtained showed that the concentration of DMSO in the reagent solution presents remarkable influence on the magnitude of analytical signal. Chemical species that could be found in the formulations such as Na(I), K(I), Mg(II), Ca(II), Ti(IV), Cl⁻, CO₃²⁻ e sodium dodecylsulfate were tested as possible interfering ions. Among them, only non-monovalent cations presented noticeable interference on lithium signal. However, they were not found in concentrations high enough to cause interference in the determination of lithium in the samples. Sample preparation was performed by sonicating a slurry prepared by dispersing 100 mg of powdered sample in 15 mL of 0.10 mol L⁻¹ HCl solution. Results obtained by developed methodology were not statistically different from those obtained by flame emission spectrometry. In the optimized conditions the method presented a linear range of 5-40 mg L⁻¹ and a relative standard deviation of 3.6% at 5 mg L⁻¹ Li concentration. Detection and quantification limits were 0.54 and 1.8 mg L⁻¹, respectively. Sampling frequency, calculated as the time interval passed between two consecutive injections, was 60 samples per hour. The methodology was successfully applied in the determination of lithium in three commercial samples.     

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Determination of lithium in pharmaceutical formulations used in the treatment of bipolar disorder by flow injection analysis with spectrophotometric detection

In this work, a flow injection system with spectrophotometric detection was developed for the determination of lithium in pharmaceutical formulations used in the treatment of bipolar disorder. Reaction between Quinizarine (1,4-dihydroxyanthraquinone) and Li(I) ion in alkaline medium containing dimethylsulfoxide (DMSO) was explored for this purpose. The flow system was optimized regarding to its chemical (DMSO, Quinizarine and NaOH concentrations and sample pH) and physical parameters (sample loop volume, carrier flow rate and reactor length) in order to establish better conditions in terms of sensitivity and sampling frequency. The results obtained showed that the concentration of DMSO in the reagent solution presents remarkable influence on the magnitude of analytical signal. Chemical species that could be found in the formulations such as Na(I), K(I), Mg(II), Ca(II), Ti(IV), Cl⁻, CO₃²⁻ e sodium dodecylsulfate were tested as possible interfering ions. Among them, only non-monovalent cations presented noticeable interference on lithium signal. However, they were not found in concentrations high enough to cause interference in the determination of lithium in the samples. Sample preparation was performed by sonicating a slurry prepared by dispersing 100 mg of powdered sample in 15 mL of 0.10 mol L⁻¹ HCl solution. Results obtained by developed methodology were not statistically different from those obtained by flame emission spectrometry. In the optimized conditions the method presented a linear range of 5-40 mg L⁻¹ and a relative standard deviation of 3.6% at 5 mg L⁻¹ Li concentration. Detection and quantification limits were 0.54 and 1.8 mg L⁻¹, respectively. Sampling frequency, calculated as the time interval passed between two consecutive injections, was 60 samples per hour. The methodology was successfully applied in the determination of lithium in three commercial samples.