Thermal and oxidative stability of Sacha Inchi oil and capsules formed with biopolymers analyzed by DSC and <Superscript>1</Superscript>H NMR

The oxidative stability of edible oils is an important feature to know due the undesirable changes that can occur in the storage. In this way, the oxidative induction time (OIT) value is an indicative to prevent this effect. The objectives of this study were to evaluate the omega-3 content and kinetic parameters of Sacha Inchi oil (SIO) and capsules that are formed with biopolymers, in addition, there were analyzed with differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H NMR). The SIO and capsules, formed using an emulsion, were analyzed with DSC in an oxygen atmosphere to determine the OIT value in isothermal conditions at 100, 120 and 150 °C. The kinetic parameters (activation energy, pre-exponential factor and z value) of SIO were obtained, and the stability time was predicted at different temperatures. The ¹H NMR spectra enabled us to assess the identification and percentage relative before and after the isothermal DSC oxidation of omega-3 concentration and formation of their oxidized compounds. (E-E)-2,4-Alkadienals were the primary oxidized compound and is strongly correlated with the decrease in omega-3 content. Isothermal DSC is a useful to determine the OIT (min) and kinetic parameters to predict the stability oxidation in different edible oils and thus prevent the inadequate consumption of edible oils oxidized.     

Water-based ferrofluids from FexPt1-x nanoparticles synthesized in organic media

This paper describes an effective method to transfer oleic acid/oleylamine-capped colloidal FePt nanoparticles dispersed in hexane into water, using tetramethylammonium hydroxide (TMAOH) as a phase transfer agent. FexPt1-x nanoparticles with different compositions (x = 0.32, 0.40, 0.48, 0.60, 0.66, 0.69) in the size range of 2-4 nm were synthesized by a high-temperature organometallic route with oleic acid and oleylamine as stabilizers. The surface of such nanoparticles was modified through removal of the organic, hydrophobic layer and adsorption of TMAOH, which provides the nanoparticles with sufficient surface charge so that an electrostatic double layer builds up, and the FePt nanoparticles can be fully redispersed in aqueous solution, even with high concentrations. The water-dispersible FePt nanoparticles were characterized by transmission electron microscopy, electrophoretic mobility, X-ray diffraction, and Fourier transform infrared spectroscopy.     

Density functional theory calculation of indirect nuclear magnetic resonance spin-spin coupling constants in C(70)

We calculate NMR spin-spin coupling constants in the C70 fullerene by means of density functional theory. We show that using a hybrid density functional (B3LYP) and an adequate basis set (cc-pCVDZ-sd), excellent agreement with experimental values can be achieved for one-bond couplings. These benchmark calculations suggest that theoretical predictions of NMR spin-spin couplings can be extremely valuable for discerning structural information of fullerenes.     

Redox chemistry of mononuclear manganese(II), binuclear manganese(III) and binuclear mixed manganese(II)-manganese(III) complexes with 3-aminopyrazine-2-carboxylate in dimethylsulphoxide

Summary Mn^II forms a yellow mononuclear species with the title ligand having a 12 stoichiometry and whose conditional stability constant is 8.9 × 10¹⁰ m ^–2. The c.v. of this complex shows an oxidation at +0.78V versus s.c.e. Controlled-potential electrolysis at +0.80V versus s.c.e. yields a binuclear species of Mn^III with a 12 metal:ligand stoichiometry.The addition of Mn^III(urea)₆(ClO₄)₃ to a solution of the ligand produces a mononuclear complex of Mn^III if the concentration of the metal ion is less than 1 mM. At higher concentrations a binuclear species is obtained. The latter is reduced in two steps, at +0.24 and –0.58 V versus s.c.e. Controlled-potential electrolysis at 0.0 V produces a dark green complex after the transfer of 0.5 equivalents of charge per mole of Mn. This binuclear L₂Mn^II-Mn^IIIL₂ mixed-valence complex can be obtained only by electrolysis of the binuclear L₂Mn^IIIMn^IIIL₂ species. Attempts to prepare the complex chemically were unsuccessful - the binuclear Mn^III species was obtained in every case.Author to whom all correspondence should be directed.     

Theoretical study of the electronic properties of narrow single-walled carbon nanotubes: beyond the local density approximation

In this work we present a systematic density functional theory study of the electronic properties of single-walled carbon nanotubes (SWNT) with diameters ranging from 3 to 5 A. In this work meta-generalized-gradient approximation, hybrid, and screened exchange hybrid functionals are utilized to compute energy band gaps in these narrow SWNT. Our calculations using hybrid functionals show that the only true exceptions to the zone folding predictions are the (4,0) and (5,0) SWNT. The remaining chiral SWNT are semiconducting with band gaps that can be as large as 1.7 eV. However, the calculated energy band gaps are significantly smaller than those predicted by the zone folding scheme. This difference is primarily attributed to the sigma-pi hybridization present in such narrow SWNT.     

Crystal structure and vibrational spectra of AlVO4. A DFT study

We present periodic density functional calculations within the generalized gradient approximation (Perdew-Wang 91) on structure and vibrational properties of bulk AlVO(4). The optimized structure agrees well with crystallographic data obtained by Rietveld refinement (the mean absolute deviation of bond distances is 0.032 A), but the deviations are larger for the lighter oxygen atoms than for the heavier Al and V atoms. All observed bands in the Raman and IR spectrum have been assigned to calculated harmonic frequencies. Bands in the 1020-900 cm(-1) region have been assigned to V-O((2)) stretches in V-O((2))-Al bonds. The individual bands do not arise from vibrations of only one bond, not even from vibrations of several bonds of one VO(4) tetrahedron. The results confirm that vibrations around 940 cm(-1) observed for vanadia particles supported on thin alumina film are V-O-Al interface modes with 2-fold coordinated oxygen atoms in the V-O((2))-Al interface bonds.     

Iron and Manganese Catalysts for the Selective Functionalization of Arene C(sp2)−H Bonds by Carbene Insertion

The first examples of the direct functionalization of non‐activated aryl sp² C?H bonds with ethyl diazoacetate (N₂CHCO₂Et) catalyzed by Mn‐ or Fe‐based complexes in a completely selective manner are reported, with no formation of the frequently observed cycloheptatriene derivatives through competing Buchner reaction. The best catalysts are Fe^II or Mn^II complexes bearing the tetradentate pytacn ligand (pytacn= 1‐(2‐pyridylmethyl)‐4,7‐dimethyl‐1,4,7‐triazacyclononane). When using alkylbenzenes, the alkylic C(sp³)?H bonds of the substituents remained unmodified, thus the reaction being also selective toward functionalization of sp² C?H bonds.     

A novel liquid chromatography-fluorescence method for the determination of delafloxacin in human plasma

Delafloxacin is a novel fluoroquinolone antibiotic that was approved by the European Medicine Agency to treat bacterial infections of the skin and underlying tissues, and community-acquired pneumonia. Despite being in the market since 2019 in the European Union, there is no published liquid chromatography-fluorescence method for delafloxacin quantification in biological samples. A novel, rapid, and sensitive high-performance liquid chromatographic method was developed to determine delafloxacin in human plasma using its native fluorescence. Plasma delafloxacin concentrations were determined by reverse-phase chromatography with fluorescence detection at 405/450 nm of excitation/emission wavelengths. Delafloxacin was separated on a Kromasil C18 column 250 × 4.6 mm id, 5 µm using isocratic elution. The mobile phase was a mixture of 0.05% trifluoroacetic acid/acetonitrile (52/48). Retention times were 5.4 and 11.6 min for delafloxacin and valsartan (internal standard), respectively. Regression calibration curves were linear over the range of 0.1–2.5 µg/mL. The lower limit of detection was 0.05 µg/mL, and the lower limit of quantification was 0.1 µg/mL. Accuracy and precision were always <11%, and the limit of quantification was <16%. Mean recovery was 98.3%. This method can be applied to determine delafloxacin in human plasma and could be useful to perform pharmacokinetic studies.     

Multiplexed Determination of Fertility-related Hormones in Saliva Using Amperometric Immunosensing

This paper reports a dual immunosensor for the simultaneous determination of two important fertility-related hormones: 17β-estradiol, E2, and follicle-stimulating hormone, FSH. The implemented method involves direct competitive (E2) or sandwich-type (FSH) immunoassays carried out on magnetic microparticles (MBs) and amperometric detection at screen-printed dual carbon electrodes (SPdCEs) involving the hydroquinone (HQ)/H₂O₂ system. The developed immune platform demonstrates LOD values of 6.88 pg mL⁻¹ and 0.11 mIU mL⁻¹ for E2 and FSH standards, respectively and usefulness for the determination in saliva samples collected from different volunteers, giving results in agreement with the conventional ELISA methodologies.