Laser-based detection of PAHs and BTXE-aromatics in oil polluted soil samples

Time-resolved laser-induced fluorescence spectroscopy and fiber optics are applied for the detection of aromatic hydrocarbons in oil contaminated water and soil samples. Time-integrated data accumulation of fluorescence intensities in an early and in a late time window with respect to the exciting laser pulse simplifies the method in such a way that it becomes very attractive for practical applications. For ultraviolet laser excitation at 337 nm and recording fluorescence signals at 400 nm, typical detection limits of the present set-up are 0.5 mg engine oil/L in water and 5 mg engine oil/kg in soil. A discrimination between BTXE-aromatics and PAHs in oil polluted soil or water samples is possible, when more than one laser wavelength in the ultraviolet is used for the excitation. The possibilities for a thermal discrimination between different aromatics are also discussed.     

A literature survey of mineral-specific sorption data on radionuclides with relevance to the disposal of radioactive waste

A comparative review of mineral-specific radionuclide sorption databases created for performance assessment and reported in both the open literature and grey literature (e.g. technical reports) has in part shown poor quality of documentation describing the database selection procedures. Inadeguate information is available on the chemical species of the radionuclide under consideration and the laboratory conditions for determining K_d-values. Sorption data derived from literature are neither comparable nor generally applicable due to the wide range in the composition of the aqueous and the solid phases applied in migration experiments. Subsequently, standardized characterization and determination procedures are needed. To improve the reliability of a mathematical model for the prediction of radionuclide sorption on cementitious and ash-type binder materials, determination of mineral-specific sorption coefficients is indispensable.     

Use of non-segmented flow,post-columns reaction detection with miniaturized HPLC systems

Summary The use of non-segmented flow, post-column reaction detection is evaluated for use with miniaturized HPLC. Non-segmented open-tubular reactors with internal diameters 0.1 mm to 0.25 mm and packed-bed reactors with internal diameters of 1 mm, filled with 5 and 10 m particles are evaluated theoretically and experimentally with respect to band broadening and pressure drop characteristics. An integrated system consisting of miniaturized HPLC (1 mm i. d.) columns and compatible hardware is described. An example of the separation of catecholamines is given.     

A convenient AC electrical conductivity (EC) apparatus

A convenient AC electrical conductivity apparatus is described. The sample, which is in the form of a pressed disk, is placed between two platinum plates located in a small cylindrical furnace. A 1–10V, 100 Hz potential is applied to the sample and the resulting current, in μA, is recorded on an X-Y recorder as a function of temperature. An EC curve of the dehydration of BaCl₂ - 2H₂O to BaCl₂ - H₂O is presented to illustrate the operation of the apparatus.     

New titrants for perchlorate and fluoroborate

Three new titrants have been evaluated for the precipitation titration of perchlorate: cetylpyridinum chloride (CPC), cetyltrimethylammonium chloride (CETAC), and benzyldimethyltetradecylammonium chloride (BDTAC). CETAC yielded the highest precision and largest potentiometric break, closely followed by CPC. BDTAC produced considerably lower precision and smaller breaks. Fluoroborate was similarly determined with CPC and CETAC. Again CETAC yielded the highest precision and largest potentiometric break. Titrations were monitored with a fluoroborate ion-selective indicator electrode and a double-junction reference electrode. The perchlorate and nitrate ISEs may also be used for monitoring the emf. Both titrants are considerably less expensive than equivalent amounts of the commonly used tetraphenylarsonium chloride titrant.     

Collinear collision of an atom with a homonuclear diatomic molecule

The problem of collinear scattering of an atom from a homonuclear diatomic molecule is formulated in terms of a first-order nonlinear matrix differential equation for the variable coefficient of reflection. For a homonuclear molecule when the target Hamiltonian is invariant under the parity transformation, only transitions between even states or odd states are possible. This selection rule reduces the number of open or closed channels that contribute to the reflection and transmission coefficients. But for numerical calculation, under the conditions of the problem, one can approximate the target Hamiltonian by the Hamiltonian of a displaced harmonic oscillator. In this approximation, the reflectional symmetry of the Hamiltonian is not preserved and transitions between any two levels of the target are possible. To simplify the problem further, the interaction between the projectile and the target is assumed to be a sum of two Gaussian terms. For this combination of the potentials the many-channel interaction can be expressed analytically. By fitting the Lennard–Jones potential with a sum of two Gaussian potentials and solving the matrix differential equation, transition probabilities are obtained for the He? H₂ collision. The numerical results are compared with the results found by Secrest and Johnson, and by Clark and Dickinson.     

Comments on the approximate calculation of lattice potential

The potential of a charge distribution due to a lattice of point charges may be evaluated by the classical multipole expansion method. The leading terms in the resultant expressions are just those used in some of our previous calculations [1–3]. In addition, for cases where the leading terms vanish because of the effect of orthogonality of the basis functions upon the Mulliken expansion (this being especially serious in the case of a one-centre charge distribution), we have derived the first nonvanishing term, involving |r|. In other cases it may be necessary to proceed to still higher multipole terms before a non-zero contribution is obtained. The entire procedure is formulated in such a way that it can be easily applied to LCAO-MO calculations for polyatomic ions in ionic lattices.     

Tellurate and periodate solutions as media for paper electrophoresis of carbohydrates

Electrophoretic separations of sugars and other polyhydroxy compounds may be performed in 0.2M telluric acid media adjusted to pH 10 with sodium hydroxide, and in 0.07M sodium metaperiodate at pH 11. Oxidation by periodate appears to be only slight under these conditions. Migration rates of 21 compounds are reported relative to the movement of d-ribose. In both electrolytes the compounds form anionic complexes.     

Zur komplexchemie von 4-zentren-π-systemen : VIII. ESR-untersuchungen an heterobutadien-chelaten. I. Kalium-(diazabutadien-tetracarbonyl-metallate)

Glyoxal- and diacetyl-bis(imine)metal tetracarbonyls (RNCR′CR′NR)M(CO)₄ (M = Cr, Mo, W) are reduced with potassium in DME to give paramagnetic mono-anions. Their high-resolutior, ESR spectra show the hyperfine splittings of the magnetically active ligand atoms as well as the satellites of the metal isotopes ⁵³Cr,^95,97Mo and ¹⁸³W. The coupling constants are discussed with respect to π-bonding mechanisms.