Kinetic Model of the Decomposition of Sodium Hydroxymethanesulfinate in Aqueous Solution

A kinetic model of the decomposition of sodium hydroxymethanesulfinate (rongalite) in aqueous solution at an initial value of pH 7.9 was considered. This multistep reaction was found to include oxidation decomposition in a solution surface layer and bulk reactions both with and without the participation of oxygen. To evaluate the parameters of this model, it was modified over three time intervals. The adequacy of this model to experimental data supported the hypothesis on the catalytic effect of active sulfur in the decomposition of rongalite.     

Determination of the Mn/Fe Ratio in Ferromanganese Nodules Using Calibration-Free Laser-Induced Breakdown Spectroscopy

Optics and Spectroscopy - The Mn/Fe ratio in ferromanganese nodules is determined by calibration-free laser-induced breakdown spectroscopy based on the use of only the plasma temperature and...     

Identification of (2-aminopropyl)benzofuran and its metabolites in human urine

An HPLC?HRMS method for the detection of the benzofuran analog of amphetamine and its metabolites in human urine using both library search and target search of the most probable metabolites based on their calculated accurate weights and fragmentation regularities is proposed. The proposed method is confirmatory. Gas chromatography–electron impact mass spectrometry with library search is proposed as the main screening method.     

Determination of copper content in soils and ores by laser-induced breakdown spectrometry

Features of electromagnetically induced transparency (EIT) in potassium vapors at the D₁ line of the ³⁹K isotope are studied. EIT resonances with a subnatural width of 3.5 MHz have been recorded upon excitation by two independent narrow-band diode lasers in a 1-cm-long cell filled with a natural mixture of potassium isotopes and buffer gas. The splitting of EIT resonances in potassium vapors in longitudinal and transverse magnetic fields has been studied for the first time. The splitted components also have a subnatural width. The smallness of the coupling factor of the hyperfine structure in ³⁹K atoms leads to a transition to the Paschen—Back regime at relatively weaker magnetic fields than in the case of Cs, Rb, and Na atoms. Practical applications of the phenomena under study are noted. The theoretical model well explains the experiment.     

Correlation between properties of a solid sample and laser-induced plasma parameters

To investigate the influence of mechanical properties of a solid sample on the laser-induced plasma parameters (temperature and mass ablated) a number of aluminum–lithium alloys and lithium ferrites with different microstructure and composition have been studied. The specific approach to estimate excitation temperature for low-resolution emission spectra has been developed. The main limitations of this approach were discussed on the basis of comparison with the energy width of several multiplets. Overall uncertainties for temperature calculation were evaluated by taking into account the accuracy of Einstein's coefficients and errors of the proposed multiplets method. The temporal evolution of laser plasma during the evaporation of these materials was studied. Extremely high value of the Li I excitation temperature has been estimated to be T > 10⁵ K for the annealed ferrite ablation, in contrast to the temperature T  1.5 · 10⁴ K for non-annealed ferrite. Only for ablation of annealed ferrite the Li II emission line at 548.4 nm was observed. It means that this laser-induced plasma was the hottest. In the case of alloys, the temperature calculated by using Li I transitions was proportional to the microhardness of the solid samples. The negative correlation between crater volume/opto-acoustic signal and alloy microhardness was observed. At the first pulses the mechanical properties of the alloys didn't correlate with the ablated mass, while the maximal correlation coefficients were observed after ablation by 10 or 50 consequent laser pulses.     

Reduction of the matrix influence on analytical signal in laser-enhanced ionization spectrometry with laser sampling

The novel approach using a slope of correlation line (laser-enhanced ionization of lithium versus laser-induced plasma emission of aluminum) as analytical signal was proposed for reduction of matrix interferences in laser-enhanced ionization spectrometric determination of Li with laser sampling.     

Removable Singularities for Fully Nonlinear Elliptic Equations

We obtain a removability result for the fully nonlinear uniformly elliptic equations F(D ² u)+f(u)=0. The main theorem states that every solution to the equation in a punctured ball (without any restrictions on the behaviour near the centre of the ball) is extendable to the solution in the entire ball provided the function f satisfies certain sharp conditions depending on F. Previously such results were known for linear and quasilinear operators F. In comparison with the semi- or quasilinear theory the techniques for the fully nonlinear equations are new and based on the use of the viscosity notion of generalised solution rather than the distributional or the weak solutions. Accepted May 3, 2000?Published online November 16, 2000     

A review of normalization techniques in analytical atomic spectrometry with laser sampling: From single to multivariate correction

Despite many advantages of laser sampling in analytical atomic spectrometry, the signal intensity of these hyphenated methods suffers from the specific influences resulting from the laser ablation process of a sample. The problems that arise affect the accuracy and precision of analytical results. Different techniques of analytical signal normalization which improve figures-of-merit for atomic spectrometry with laser sampling are considered in this review. The characteristics and application of these approaches including the use of internal standards, single or several reference signals and multivariate correction of analytical signal are discussed.