Voltammetry as a Reference Method in the Preparation Process of Plant Control Material Containing As,Pt and Tl

Voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices after thorough mineralization. In the presented work, voltammetric methods were used as reference methods in the preparation process of control plant material. Determination of As, Pt, Tl and other elements (Cd, Cu, Pb, Zn) in plant material prepared in our laboratory is described. For quantitative determination of the elements two independent analytical methods were applied. To obtain plant material containing As, Pt and Tl white mustard (Sinapis alba L.) was hydroponically cultivated under controlled conditions in a nutrient solution with addition of As, Pt and Tl salts.     

Magnetic resonance study of carbon encapsulated Ni nanoparticles

Magnetic resonance study of six samples consisting of carbon encapsulated nickel nanoparticles or carbon nanotubes ended with such nickel nanoparticles was carried out at room temperature. Samples of Ni/C were prepared by carburization of nanocrystalline nickel by ethylene (C₂H₄) and methane (CH₄). Hydrocarbons decomposition on nickel nanoparticles was done at temperatures 500, 600 and 700°C. Magnetic resonance spectra of samples designated as CH₄/500, CH₄/600, CH₄/700, C₂H₄/500, C₂H₄/600 and C₂H₄/700 were obtained by Bruker E 500 spectrometer. The integrated intensities of the resonance spectra were correlated with the carburization conditions (temperature, type of hydrocarbon) during samples preparation. A core-shell model of the investigated samples allowed rough estimation of appropriate shell sizes.      

Ion-selective electrode for measuring low Ca2+ concentrations in the presence of high K+, Na+ and Mg2+ background

In this work, ion-selective electrodes for calcium ion were investigated. Two ionophores were used in the membranes: ETH 1001 and ETH 129. An internal filling solution buffered for primary ion was used that allowed the lower detection limit to be decreased down to 10^−8.8 M. Theoretical and experimental electrode characteristics pertaining to both primary and interfering ions are discussed. Better behavior was obtained with the electrode prepared with ETH 129 in the membrane. This electrode would be the most likely candidate for obtaining a low Ca²⁺ detection limit in measurements performed with high K⁺, Na⁺, Mg²⁺ background, which is found inside the cells of living organisms, for example. The potentiometric response of the electrode in solutions containing main and interfering ions is in good agreement with simulated curves obtained using the Nernst–Planck–Poisson (NPP) model.     

Weak convergence of products of sums of independent and non-identically distributed random variables

We study limit properties in the sense of weak convergence in the space D[0,1] of certain processes based on products of sums of independent and non-identically distributed random variables. The obtained results extend and generalize results known in the i.i.d. case.     

1,3‐Alternate calix[4]arene‐bonded silica stationary phases. Effect of calixarene skeleton substituents on the retention mechanism and column selectivity

Four novel 1,3‐alternate calix[4]arene‐bonded silica gel stationary phases possessing different aromatic and aliphatic substituents at the upper rim (CalixNph, CalixBph, CalixHex, and CalixDdc) were prepared and structurally characterized. The comparison and selectivity of these phases were done by using alkylbenzenes, fatty acid p‐bromophenacyl esters, aromatic positional isomers, and polynuclear aromatic hydrocarbons as analytes. Quantum chemistry calculations have also been performed (using an ab initio method) to support the experimental findings. The effect of the type and content of organic modifier on the retention and selectivity of the alkylbenzenes was studied. The retention mechanism is also discussed. The results indicate that the stationary phases behave like RP packings. However, inclusion complex formation and hydrophobic and π–π interactions seem to be involved in the separation process.     

The binary system PbO - BiVO4

Phase equilibria established in the PbO - BiVO₄ system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using DTA and XRD.      

Synthesis of Four Enantiomers of (1-Amino-3-Hydroxypropane-1,3-Diyl)Diphosphonic Acid as Diphosphonate Analogues of 4-Hydroxyglutamic Acid

All the enantiomers of (1-amino-3-hydroxypropane-1,3-diyl)diphosphonic acid, newly design phosphonate analogues of 4-hydroxyglutamic acids, were obtained. The synthetic strategy involved Abramov reactions of diethyl (R)- and (S)-1-(N-Boc-amino)-3-oxopropylphosphonates with diethyl phosphite, separation of diastereoisomeric [1-(N-Boc-amino)-3-hydroxypropane-1,3-diyl]diphosphonates as O-protected esters, followed by their hydrolysis to the enantiomeric phosphonic acids. The absolute configuration of the enantiomeric phosphonates was established by comparing the ³¹P NMR chemical shifts of respective (S)-O-methylmandelic acid esters obtained from respective pairs of syn- and anti-[1-(N-Boc-amino)-3-hydroxypropane-1,3-diyl]diphosphonates according to the Spilling rule.     

Chemical Components of Oxytropis pseudoglandulosa Induce Apoptotic-Type Cell Death of Caco-2 Cells

Oxytropis pseudoglandulosa plant is used in traditional Mongolian medicine. However, its chemical composition and biological properties are poorly explored. In this study, the total content of polyphenols and flavonoids as well as antioxidant activity were verified in plant extract. The total phenolic and flavonoid contents were determined by spectrometric (6.62 mg GAE/g and 10.32 mg QE/g) and chromatographic (17,598 mg/kg and 17,467 mg/kg) assays. The antioxidant potential was investigated by DPPH assay and yielded IC₅₀ at 18.76 µg/mL. Twelve phenolic compounds were identified as components of O. pseudoglandulosa extract. Kaempferol-3-O-robinosyl-7-O-rhamnoside and kaempferol-3-(p-coumaroyl)-rutinosyl-7-rhamnoside made up 80% of determined components and were found to be the major polyphenolic compounds. The biological properties of O. pseudoglandulosa extracts were determined in vitro using human epithelial adenocarcinoma Caco-2 cell line. Low concentrations of extract (0–30 µg/mL) exhibited protective effects against cell damage caused by chemically induced oxidative stress. Elevated concentrations, on the other hand, resulted in apoptotic-type cell death induction. Metabolic failure, ROS elevation and membrane permeabilization observed in cells upon incubation with extract dosages above 50 µg/mL allowed us to conclude on O. pseudoglandulosa being predominantly a necrosis inducer.     

Sensitive adsorptive stripping voltammetric procedure of Imatinib determination in spiked urine samples using solid lead microelectrode

This article reports for the first time the application of solid lead microelectrode for organic compound determination. The proposed sensor was used for anticancer drug Imatinib quantification by adsorptive stripping voltammetry. Procedure of Imatinib determination was developed utilizing advantages ensured by solid lead microelectrode: reusability and durability for a long period of time and its ecological character as compared to film electrodes. The detection limit of Imatinib determination was calculated to be 1.9 × 10⁻¹⁰ mol L⁻¹. The analytical usability of the developed procedure was confirmed by acceptable recoveries of Imatinib determination in spiked urine samples.