Flow methods for the determination of elements in solutions based on sorption preconcentration and inductively coupled plasma mass spectrometry

Methods involving an on-line combination of sorption preconcentration with the determination of elements by inductively coupled plasma mass spectrometry (ICP-MS) are considered. The reasons for the effect of the composition of the solution on the analytical signals in the determination of elements, the issues related to recording of nonstationary signals, and the procedures for the sorption preconcentration of elements in the corresponding flow systems are discussed. Some examples of the determination of elements in environmental samples, biological fluids, and other samples are given.     

tert-Butylthiacalix[4]arene monolayers as a biomimetic model for the oxidation of antioxidants with cytochrome c

The possibility of designing a model of sensor to antioxidants based on thiacalix[4]arene monolayers with immobilized cytochrome c was shown. The molecular surface area S ₀ of thiacalix[4]arene in the monolayers and the surface pressure coefficient ?dπ/dS (elasticity) reflect changes in the redox state of cytochrome c in the presence of dihydroquercetin and ascorbic acid in the aqueous subphase. The absorption spectra in the visible and UV ranges of solutions of the subphase and transferred thiacalix[4]arene monolayers with immobilized cytochrome c confirm the oxidation of the antioxidants to quinones and formation of the reduced form of cytochrome c.     

The Barkhausen thermal effect as applied to investigation of the polarization switching of barium strontium niobate crystals

The thermally stimulated transformation of the domain structure of barium strontium niobate crystals with chromium and cerium photorefractive impurities is investigated using the Barkhausen thermal effect for the first time.     

Spontaneous polymerization of acrylamide in glycerol: Active centers and specific features

The nature of active centers and the specific features of the spontaneous polymerization of acrylamide in glycerol in the range 300-77 K have been studied. Glycerol activation is needed for polymerization. At this stage, active intermediate species are formed and stabilized under the action of photo-and γ radiation. Intermediate species are hydroperoxide compounds resulting from the sensitized (through technical traces) photolysis (or radiolysis) of glycerol. The decomposition of hydroperoxides into radicals on addition of finely dispersed acrylamide powder into the activated glycerol yields primary acrylamide radicals that initiate the growth of polymer chains.     

Growth, optical parameters, and spectroscopic properties of crystals of disordered scheelite-like molybdates NaLaxGd1 ? x(MoO4)2 (x = 0–1) activated by Tm3+ ions

Polarized optical absorption spectra in the range of 450–2000 nm have been recorded for the Czochralski-grown concentration series of single crystals of mixed scheelite-like molybdates NaLa _x Gd_{1 − x} (MoO₄)₂(x = 0–1) activated by Tm³⁺ ions. The intensity parameters Ω _t (t = 2, 4, 6) of the crystals grown were determined by the Judd-Ofelt method, and the values found were used to estimate the probabilities and emission branching ratios for a number of radiative transitions of Tm³⁺ ions. The main optical constants of an Na_0.909La_0.490Gd_0.498Tm_0.035Mo_2.020O_8.048 crystal were found and the temperature dependences of the refractive index for the ordinary and extraordinary waves were investigated in the temperature range of 293–373 K. The spectral dependences of the emission cross section for the expected ³ F ₄ → ³ H ₆ laser transition of Tm³⁺ ions in an Na_0.908La_0.301Gd_0.676Tm_0.048Mo_2.019O_8.043 crystal were measured in the spectral range of 1500–2000 nm. The gain cross section of the active medium on the ³ F ₄ → ³ H ₆ laser transition of Tm³⁺ ions in this crystal was calculated using the spectral dependences of the absorption and emission cross sections.     

The Influence of Dung Amendments on Dissolved Organic Matter in Grassland Soil Leachates - Preliminary Results from a Lysimeter Study

Abstract

Understanding the carbon (C) cycle in grassland pasture systems requires more information about the fate of decomposing dung material within the soil. In this soil lysimeter study we successfully applied the natural ¹³C abundance labelling technique to trace dung-C within a temperate grassland soil. Dung was collected from beef steers fed on either maize (a C₄ plant) or perennial ryegrass (a C₃ plant) silages, and applied to a freely draining (C₃) grassland soil. Leachates were collected from soil lysimeters (0–2.5) and (0–10 cm soil depth) to determine the organic carbon and ¹³C content of < 0.7 μm filtered solution. Leachates were taken from (i) control, no dung added, (ii) C₃ dung and (iii) C₄ dung amended soil. Results showed that, (i) the addition of dung resulted in a tenfold increase in C lost from the lysimeters in drainage waters, (ii) up to 50% of the C present in the leachates was ‘native’ soil C and (iii) the application of dung produced a ‘priming’ effect. Further work is required to verify; (i) whether increased leaching of native C following dung application is a ‘true priming’ phenomenon, or merely the result of ‘displacement’ or ‘pool substitution’ of soil C, and (ii) the precise conditions and mechanisms under which organic amendments induce a true ‘priming’ effect in grassland and other agricultural soils.     

Intensity of the <Emphasis Type="Italic">f-f</Emphasis> transitions of Nd<Superscript>3+</Superscript>, Er<Superscript>3+</Superscript>, and Tm<Superscript>3+</Superscript> rare-earth ions in calcium niobium gallium garnet crystals

This paper reports on the results of the investigation into the intensities of the f-f transitions of Nd³⁺, Er³⁺, and Tm³⁺ ions in calcium niobium gallium garnet (CNGG) crystals. The values of the oscillator strengths and line strengths obtained for hypersensitive transitions and the intensity parameters Ω _t of the rare-earth ions in the CNGG crystals are compared with the corresponding quantities for crystals of other garnets and some oxide and fluoride crystals. The assumption is made that an increase in the oscillator strengths and line strengths for the hypersensitive transitions and the intensity parameters Ω₂ of the Nd, Er, and Tm ions in the CNGG crystals as compared to those for crystals of other garnets is associated with the specific features revealed in the crystal structure of the calcium niobium gallium garnet, in particular, with the lowering of the symmetry of the positions occupied by rare-earth ions in the crystal structure.     

Structure and properties of 4-phenyl-5H-1,2,3-dithiazole-5-thione polyiodide with S−I+−S bridged complex

Structural Chemistry - Treatment of 4-phenyl-5H-1,2,3-dithiazole-5-thione with iodine in acetonitrile yielded crystalline product with thione-iodonium three-center halogen bond and triiodide anion...     

Low-Temperature Photolysis of Benzoyl Peroxide

Russian Journal of Physical Chemistry A - The photolysis of dry benzoyl peroxide (BP) at 77 K in the 480–236 nm range of wavelengths and an ethanol solution is studied via EPR. It is...