Activity of copper–cerium–zirconium catalysts in oxidation of hydrogen

We have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–1000 °C. We have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.     

Analysis of Nanafrocin in Foodstuffs of Animal Origin by LC–MS–MS

A new, rapid, and efficient method, multiple reaction monitoring liquid chromatography–tandem mass spectrometry, has been developed for analysis of nanafrocin in foodstuffs of animal origin. The researchers used a C₁₈ stationary phase coupled with triple-quadrupole tandem mass spectrometry in negative-electrospray mode. The limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.01 mg kg^?1, respectively, in the matrixes. Detector response was found to be a linear function of concentration over the range 0.005–0.1 mg kg^?1 in each matrix. Mean overall recovery (n = 10) of nanafrocin varied from 71 to 101%. The results show that identification and quantification of nanafrocin residues in foodstuffs of animal origin can be successfully achieved by use of the proposed LC–MS–MS method.     

MSPD–GC–MS–MS Determination of Residues of 15 Organic Nitrogen-Containing Pesticides in Vegetables

A novel and simple method for determination of 15 organic nitrogen-containing pesticides in vegetables using matrix solid-phase dispersion (MSPD) coupled with gas chromatography tandem mass spectrometry (GC–MS–MS) has been developed. The efficiencies of different sorbents (florisil, silicone, neutral alumina) for the MSPD were compared. Mean recoveries of the method using neutral alumina varied from 73.26 to 111.83% with relative standard deviations of 0.79–15.33% in the concentration range of 0.01, 0.02 and 0.05 mg kg^?1. The limits of detection were typically in the 0.0007–0.0320 mg kg^?1 range, which were 10–100 times lower than the maximum residue levels established by the European Union. This method was applied to residue detection in vegetables, in which organic nitrogen-containing compounds were detected at low concentrations.     

LC–MS–MS Determination of Nikethamide in Human Plasma

A sensitive LC–MS–MS method with electrospray ionization has been developed for determination of nikethamide in human plasma. After addition of atropine as internal standard, liquid–liquid extraction was used to produce a protein-free extract. Chromatographic separation was achieved on a 150 mm × 2.1 mm, 5 μm particle, Agilent Zorbax SB-C₁₈ column, with 45:55 (v/v) methanol–water containing 0.1% formic acid as mobile phase. LC–MS–MS was performed in multiple reaction monitoring mode using target fragment ions m/z 178.8 → 107.8 for nikethamide and m/z 289.9 → 123.8 for the internal standard. Calibration plots were linear over the range of 20.0–2,000 ng mL^?1. The lower limit of quantification was 20.0 ng mL^?1. Intra-day and inter-day precisions were better than 4.2 and 6.1%, respectively. Mean recovery of nikethamide from human plasma was in the range 65.3–71.1%.     

LC–ESI–MS Determination of Flupentixol in Human Plasma

Flupentixol and an internal standard, loperamide were extracted from human plasma by liquid–liquid extraction and analyzed on a Thermo Hypersil HyPURITY C18 column, with 10 mM ammonium acetate–acetonitrile–methanol (26:62:12, v/v/v) as mobile phase, coupled with electrospray ionization mass spectrometry (ESI–MS). The protonated analyte was quantified by selected-ion monitoring (SIM) with a quadrupole mass spectrometer in a positive-ion mode. The calibration curve was linear (r = 0.9990) over the concentration range: 0.039–2.5 ng mL^?1. Intra-day and inter-day precision (RSD%) were less than 13.05%. The established method was successfully applied for the determination of pharmacokinetics of flupentixol in human plasma.     

SPE–GC–MS Analysis of Chloroform in Drinking Water

In this paper we report a method based on solid-phase extraction (SPE) and subsequent analysis by gas chromatography combined with mass spectrometry for determination of chloroform in potable water. The affinity of chloroform for the resin enables almost complete recovery of the analyte. The analytical method proposed enables evaluation of chloroform levels down to 0.295 g L^–1. The procedure is characterized by lack of interferences, in fact the GC–MS analysis reveals the presence of only one peak, that of chloroform. Use of CDCl₃ as labelled internal standard also makes the procedure suitable for use as a reference analytical method for quantification of chloroform in drinking water.     

LC–ESI–MS Determination of Lovastatin in Human Plasma

A convenient, selective and sensitive liquid chromatographic-electrospary ionization mass spectrometry (LC–ESI–MS) method was developed and validated to determine lovastatin in human plasma. The analyte was extracted from human plasma samples by typical liquid–liquid extraction, separated on a C₁₈ column by using the mobile phase consisting of water–methanol (13:87, v/v). Simvastatin was used as the internal standard (IS). The method was linear within the range of 0.1–20 ng mL⁻¹. The lower limit of quantification (LLOQ) was 0.1 ng mL⁻¹. The intra- and inter-run precision, calculated from quality control (QC) samples was less than 10.2%. The accuracy as determined from QC samples was in the range of 99.3–102.9% for the analyte. The mean recoveries for lovastatin and IS were 84.8 and 88.0%, respectively. The method was successfully applied for evaluation of the pharmacokinetic of lovastatin in healthy volunteers.     

Study of the precision in the purge-and-trap–gas chromatography–mass spectrometry analysis of volatile compounds in honey

Data precision in the analysis by purge-and-trap coupled on-line to gas chromatography–mass spectrometry (P&T-GC–MS) of honey volatiles has been studied by statistical analysis. The contribution of non-random factors to dispersion of quantitative results was proven by comparing several statistical parameters (correlation coefficients, principal component analysis (PCA) eigenvalues and loadings) from both experimental and simulated data. PCA was also useful for grouping volatiles with similar dispersion behaviour; these groups being generally related to compounds with common properties or structural features. The use of area ratios improves data precision for compounds within the same group. Results from this study could be used for a better selection of internal standards in quantitative analysis of volatiles by P&T-GC–MS.     

GC–MS Determination of Sucralose in Splenda

Sucralose (1,6-dichloro-1,6-dideoxy-β-d-fructofuranosyl-4-chloro-4-deoxy-α-d-galactopyranoside) is a high-intensity non-nutritive sweetener derived from sucrose. Determination of sucralose in food is important to ensure consistent product quality. The authors have developed a new method for determination of sucralose. The sucralose was converted into its trimethylsilyl (TMS) ether and qualitative and quantitative analysis were achieved by GC–MS and GC–FID, respectively, using myo-inositol ester as the internal standard. A good linear relationship between response and amount of sucralose TMS ether was obtained in the range 0.005–0.06 mg mL^?1 (r = 0.9994). The detection limit was 0.25 ng.     

Molecular thermodynamics of salt effect in vapor–liquid equilibrium of ethanol–water systems

Scaled particle theory was used to derive a general expression for the salt effect parameter, K, of isobaric vapor–liquid equilibrium for ethanol–water-1-1 type electrolytic systems, which appears in the Furter equation. This expression was essentially a sum of two terms: 1, the hard sphere interaction term calculated by Masterton–Lee's equation, 2, the soft sphere interaction term calculated by Y. Hu's molecular thermodynamical model, in which the diameters of nacked ions were replaced by that of solvated ions, the solvation coefficients (i.e., in the radio of the latter to the former) were taken to be adjustable parameters, their magnitude implies the ionic solvation rules. A correlation equation for the local dielectrical constant around central ions with liquid concentration was obtained by mapping out experimental points. The calculated salt effect parameters of 9 ethanol–water-1–1 type electrolytic systems were in good agreement with the literature values within the wide range of liquid concentration.     

Specific features of phase equilibriums in Ln–Ba–Fe–O systems

Formation of five-layered Ln_2–εBa_3+εFe₅O_15–δ phases [exhibiting nanoscale ordering with layer-by-layer location of the cations in the Ln–Ba–(Ln,Ba)–(Ln,Ba)–Ba–Ln perovskite-type structure] has occurred in the Ln–Ba–Fe–O (Ln = Y, Pr, Nd, Sm, Eu, and Gd) systems at 1100°С in air. Partial substitution of iron with cobalt (Ln_2–εBa_3+εFe_5–yCo_yO_15–δ, Ln = Nd, Sm, Eu) has stabilized formation of the ordered structure. The oxygen content in the complex oxides has been determined in air over a wide temperature range by means of high-temperature thermogravimetry and iodometric titration. The change in oxygen content with temperature for the phases with five-layered ordering was significantly smaller than for the disordered phases.     

Synthesis of quasi-crystalline phases in the Al–Cu–Fe–Cr system

Phase equilibria in the Al–Cu–Fe system alloyed with 5% Cr were studied. Based on the data of X-ray powder diffraction analysis, electron microscopy, and differential thermal analysis, the effect of temperature on i ? d phase transitions in alloys Al₆₅Cu₂₅Fe₅Cr₅ and Al₇₀Cu₂₀Fe₅Cr₅. In the Al–Cu–Fe–Cr system, multiphase structures were detected; these structures are mixtures of quasi-crystalline and approximant phases, the contents and morphologies of which depend on the composition of the initial mixture and the crystallization rate.     

Formation of short-range order in Al–Ge–Fe melts: influence of composition

ABSTRACT

The short-range order in Al–Ge–Fe melts has been studied by X-ray diffraction and reverse Monte Carlo simulations in wide concentration range. Influence of the replacement of one component by another while the content of third component is constant on the formation of a local structure of ternary melts has been discussed. It has been shown that at Ge content less than 30 аt. % Ge atoms are uniformly distributed in the volume of the Al–Ge–Fe melts and atomic clusters with structure similar to the liquid germanium are formed at content more than 30 аt. % Ge. The addition of the third component (Ge or Al) to the binary Al–Fe or Fe–Ge melts, correspondingly, results in competition between Al and Ge atoms in formation of the local structure around Fe atoms. The obtained concentration dependences of the nearest neighbour distances point out that the ternary interactions take place in the Al–Fe–Ge melts.     

Deactivation of a mixed oxide catalyst of Mo–V–Te–Nb–O composition in the reaction of oxidative ethane dehydrogenation

The operational stability of a mixed oxide catalyst of Mo–V–Te–Nb–O composition in the oxidative dehydrogenation of ethane (ratio of C₂H₆: O₂ = 3: 1) is studied in a flow reactor at temperatures of 340–400°C, a pressure of 1 atm, and a WHSV of the feed mixture of 800 h^?1. It is found that the selectivity toward ethylene is 98% at 340°C, but the conversion of ethane at this temperature is only 6%; when the temperature is raised to 400°C, the conversion of ethane is increased to 37%, while the selectivity toward ethylene is reduced to 85%. Using physical and chemical means (XPS, SEM), it is found that the lack of oxidant in the reaction mixture leads to irreversible changes in the catalyst, i.e., reduced selectivity and activity. Raising the reaction temperature to 400°C allows the reduction of tellurium by ethane, from the +6 oxidation state to the zerovalent state, with its subsequent sublimation and the destruction of the catalytically active and selective phase; in its characteristics, the catalyst becomes similar to the Mo–V–Nb–O system containing no tellurium.     

Development of X-ray fluorescence analysis in Russia in 1991–2010

A review attempted to examine the results of studies in X-ray fluorescence (XRF) analysis performed by Russian authors for the period from 1991 to the present time is given. This proved to be quite a challenge, since the number of articles published only on the theory and practice of XRF (excluding the development of equipment) exceeded 500. Therefore, the author had to limit himself to a more detailed presentation of only several important achievements. Further information, if necessary, can be found in the cited reviews.     

Corrosion Behavior of Quasi-Crystalline Alloys of the Al–Cu–Fe–Cr System in Alkaline Media

Russian Journal of Electrochemistry - The electrochemical behavior of three alloys of different composition in the system Al65Cu25Fe10 – хCrх is studied by the potentiodynamic...     

Quantification of phytochelatins in plants by reversed-phase HPLC–ESI–MS–MS

An on-line HPLC–ESI–MS–MS method has been developed for determination of glutathione and phytochelatins (PC) in plant tissues. For sample pretreatment, dithiothreitol (DTT) must be added at the very beginning, as an anti-oxidant. Optimization of instrumental conditions i.e. composition of HPLC mobile phase, ionization efficiency of the electrospray interface, and MS–MS detection in the multiple ion-monitoring mode, are the central aspects of this work. A polystyrene-packed column was found to be superior to a standard silica-packed reversed-phase column. A concave quadratic gradient of ammonium formate buffer and acetonitrile was found to be optimum. The limits of quantitation were 0.2 mol kg^–1 plant tissue for glutathione and PC. The method has been applied to analysis of tissue samples from Vicia faba grown in Cd-containing nutrient solutions.Dedicated to the memory of Wilhelm Fresenius     

Physicochemical properties of binary solutions of propylene carbonate–acetonitrile in the range of 253.15–313.15 K

The density, dynamic viscosity, and dielectric constant of propylene carbonate solutions with acetonitrile are measured over the composition of a mixed solvent at temperatures of 253.15, 273.15, 293.15, and 313.15 K. The molar volume, molar viscosity, and molar capacity of a mixture of propylene carbonate–acetonitrile and an excess amount of it are calculated. The effect the temperature and composition of the mixture have on the excess molar properties is discussed. A linear correlation is observed between the values of the molar fluidity, capacity, polarization, and molar volume of the studied system.     

Microcalorimetric Evaluation of Precipitation in Cu–2Be–0.2Mg

Beryllium precipitation from the Cu-rich matrix in a Cu–2 mass% Be–0.2 mass% Mg alloy homogenized and quenched from 1073 K was studied by differential scanning calorimetry (DSC). The DSC traces showed two main exothermic effects, A and B, each comprising two subeffects: A₁ and A₂ , and B₁ and B₂ respectively. Effects A₁ and A₂ correspond to the precipitation of GP zones and subsequent overlapping and independent precipitation of the phase. Only at very low heating rates can be inherited from GP zones. Effects B₁ and B₂ correspond to heat evolved during transitions to the states with and phases, respectively. Heat effect A can be quantitatively described in terms of solid solubilities before and after precipitation, and of the precipitation heats of the phases involved. The heat content of the combined GP zone/ phase precipitation effect was proportional to the number of beryllium atoms precipitated, yielding an average value of 21 kJ mol^–1 beryllium for beryllium precipitation. It was shown that the phase arises from the combined transition from states with GP zones and phases, whereas arises from the transition of states with and phases. The apparent activation energies associated with GP zones and , and phases are 1.16±0.08, 1.18±0.07, 1.37±0.08 and 1.74±0.09 eV, respectively. These values are discussed in terms of the mobility of dissolved atoms related to the concentrations of excess vacancies and solute-vacancy complexes, and the direction of plate-like precipitate growth (either normal or perpendicular to the plate). It is inferred that the main roles of magnesium are to decrease the amount and rate of GP formation, to enhance the volume fraction of and to suppress the discontinuous precipitation of .This revised version was published online in November 2005 with corrections to the Cover Date.     

Novel structural behaviour of iron in alkali–alkaline-earth–silica glasses

The combined effect of alkali and alkaline-earth ions on the redox, distribution, co-ordination and environment of Fe ions in alkali–alkaline-earth–silica glasses has been studied using a multi-technique approach. Wet chemical analysis and Mössbauer, electron spin resonance (ESR), optical absorption and photoluminescence spectroscopies were utilised. Behaviour generally falls into two categories, which we have termed ‘collective’ and ‘selective’. Collective behaviour occurs when alkali and alkaline-earth ions have similar effects on a property and the overall effect is cumulative. This is characterised by a linear relationship with optical basicity of the glass. Some parameters associated with the environment of Fe²⁺ ions fall into this category. Selective behaviour occurs when alkali and alkaline-earth ions have opposing effects on a property, suggesting competition or selectivity. This is characterised by a linear relationship with the alkali/alkaline-earth ionic radius ratio, cation field-strength ratio or oxide-basicity ratio. The Fe²⁺/ΣFe ratio and several parameters associated with the distribution, coordination and environment of Fe³⁺ ions fall into this category. These results have implications for the local structure surrounding Fe species. A relationship has been suggested linking coordination and distribution of Fe³⁺ ions.