New sources of “active” halogen bis(dialkylamide)hydrogen dibromobromates, efficient reagents for destruction of ecotoxicants

Bis(dialkylamide)hydrogen dibromobromates were synthesized and their reactivity was investigated in decomposition of diethylphosphonic, diethylphosphoric, and 4-toluenesulfonic acids 4-nitrophenyl esters. The nucleophilic reactivity of a typical α-nucleophile, hypobromite ion, is independent of the source of the active bromine. The cetyltrimethylammonium dibromobromate is a unique reagent for destruction of ecotoxicants. In weakly alkaline media the half-life of 4-nitrophenyl diethylphosphonate did not exceed 6 s at [BrO^?] 0.02 mol l^?1, and the apparent reaction rate compared to water increased ～40-fold. The main factor governing the micellar effects of surfactants is concentrating the substrate in the micellar pseudophase.     

Intracavity laser polarization spectrometer for biomolecule traces

A polarization variant of an intracavity laser spectrometer based on the competition of beams in an argon ion laser, radiating a number of narrow lines in the 275 to 529 nm spectral range, is proposed and described for the spectral analysis of liquid samples, having broad absorption bands, mainly biomolecules in solutions. By careful optimization of the operating conditions, a procedure has been established that results in a minimal measurable absorbance decreased up to 10(-5) units of optical density. The examined spectrometer provides a wide dynamic range of analysis. A determination of trace contents of amino acids in methanol were carried out.     

Intracavity UV-range laser spectrometer

We suggest a variant, which has already been implemented, of a selective intracavity laser spectrometer with intracavity nonlinear optical conversion of the frequency range of generated multimode radiation. The apparatus provides a means for transition into the UV spectral range (shorter than 300 nm) to carry out direct recording and quantative investigation of strong resonance lines of atomic absorption, which earlier were beyond the reach of the intracavity method. We measured selective absorption in spectral lines of a number of metals: FeI 296.690 nm, TiI 294.200 nm, and GaI 287.424 nm. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skorina Ave., Minsk, 220072, Belarus; e-mail: Ild@imaph.bas-net.by. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 875–879, November–December, 1999.     

Development of a laser-induced breakdown spectroscopy method for soil and ecological analysis (review)

The application of laser spectrochemical analysis to testing for basic compounds and nutritious/toxic elements in soil has been reviewed. A combined laser-spark approach has been applied for the rapid measurement of the carbon content in soil. Spectra have been excited both directly in a laser-ablation plume and by passing a pulsed electric discharge through the plume. The emission spectrum intensity in the combined plasma is considerably higher. The application of a complex of methods to carbon determination in soil has shown that in fact the data on the humus content usually obtained in agrochemical practice by a conventional method of carbon oxidation by potassium dichromate need to be corrected taking into account the possibility of incomplete oxidation of organic matter in soil. The efficiency of various double-pulse LIBS applications has been demonstrated in solving a number of environmental problems such as the determination of heavy and toxic metals in soil and the detection of sulfur in coal. The instrumentation and analytical procedures have been proposed and optimized for rapid control of the chlorine content in plant samples. The technique can be easily extended to ecological monitoring of toxic elements and heavy metals in any biogenic material.     

Synthesis of tungsten carbide nanopowder via submerged discharge method

Tungsten carbide nanopowder was prepared via pulsed discharge of bulk tungsten and graphite rods immersed in pure ethanol. The effect of discharge parameters on the characteristics of final products was investigated. Structural and morphological characterization of nanopowder was performed by means of X-ray diffraction analysis and transmission electron microscopy. In order to determine the feasibility of using synthesized material as an electrocatalyst, tungsten carbide nanopowder was tested for hydrogen evolution. A correlation was found between morphology of nanoparticles, their phase composition and electrocatalytic activity.     

Intracavity laser atomic absorption spectrometry with graphite furnace atomizer or pulsed laser sampler

An absorption intracavity laser spectrometer with two types of sample vaporization systems (graphite furnace electrothermal atomizer or laser sampler) is described that can be used for the determination of trace amounts of metals (Al, Cr, Fe and Mn) in liquid samples and at the surface of solid targets. The limits of detection for the elements tested are lower than those obtained by modern conventional spectrometers. The examined technique provides a wide dynamic range of linear standard calibration curves.