Determination of imazalil by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

A simple, rapid and reproducible capillary isotachophoretic on-line coupled with capillary zone electrophoresis (CITP-CZE) method for the determination of IMz in food packaging extracts and its residues in apples is described. A good separation of the IMZ from other sample constituents was achieved within 15 minutes without any sample clean up. Method characteristics (linearity, accuracy, intra-assay and detection limit) were determined. Less amount of time involved, sufficient sensitivity and low running cost are the important attributes of CITP-CZE method.     

Kinetic Determination of Microquantities of Rutin by Perturbation of the Bray-Liebhafsky Oscillatory Reaction in an Open System

A kinetic method is described for the microquantitative (microconcentration/microvolume) determination of rutin based on potentiometric monitoring of the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory reaction being in a non-equilibrium stationary state close to a bifurcation point. The experiments are carried out in an open reactor. The response of the matrix system to perturbations by different concentrations of rutin ethanolic solutions is followed by a Pt-electrode. In the concentration range between 7.8×10^–8moldm^–3 and 9.1×10^–6mol dm^–3, we found a linear dependence of the maximal potential shift, E_m, on the logarithm of the rutin concentrations. The unknown concentrations can be determined from the calibration curve up to an accuracy of ±5%. The detection limit is 3.6×10^–8mol dm^–3. The amount of required sample can be as small as 10µL.     

Sorption of caesium and strontium on clinoptilolite-and mordenite-containing sedimentary rocks

The sorption of caesium and strontium from its aqueous solutions by ten clinoptilolite-and mordenite-containing sedimentary materials from Slovakia, Bulgaria, Ukraine and Greece was investigated by batch-type procedure and radiotracer techniques. The concentration of the solutions, that were performed in and without the presence of competing cations (0.005 mol·dm⁻³ KCl) varied between 1·10⁻⁴ and 5·10⁻² mol·dm⁻³. The uptake and distribution coefficient (K _d ) values determined for the materials of the different origin, were correlated with their mineralogical composition and gross cation exchange capacity (CEC). The identification of the specific uptake sites was attempted on the basis of the sorption isotherms and the content of exchangeable cations. The experimental results provide information on the suitability of the individual materials for the treatment of radioactive wastes and their application as backfills in potential nuclear waste repositories.     

Determination of hydrochloric acid in organic solutions by gas chromatography

Summary A method is described for the determination of small quantities of hydrochloric acid in two chlorinated organic solvents (CHCl₃ and CCl₄). An excess of gaseous ethylene oxide is added to a liquid sample; the 2-chloroethanol formed is then analyzed by gas chromatography. The procedure is simpler and more sensitive in comparison with other conventional methods. It can be modified for other organic solvents.D.G.R.C.S.T. grant.     

Kinetics of the dehydration of CsNd(SO4)2 4 H2O

The kinetics of the dehydration of CsNd(SO₄)₂ · 4 H₂O to CsNd(SO₄)₂ · H₂O and then to CsNd(SO₄)₂ are studied by isothermal weight change. The reactions are phase-boundary-controlled. Reaction mechanism and activation energy depend on sample weight.     

Calcium-selective electrodes based on calcium tetra(4-chlorophenyl)borate complexes of macrocyclic polyether diamides

The preparation of macrocyclic 7,19-dibenzyl-7,19-diaza-1,4,10,13,16-pentaoxa-cycloheneicosane-6, 20-diones substituted in positions 2 and 3 with methyl groups, and their properties in PVC membranes as calcium sensors are described. Complexes of these polyether diamides (PEDA) with calcium and tetra(4-chlorophenyl)borate (TClPB) ions having the composition 2PEDA·Ca·2TClPB were prepared. Calcium electrodes based on these complexes have selectivity coefficients for calcium over barium up to 10³, and over alkali metals up to 3 × 10⁴.     

Preparation and NMR spectra of substituted 2-phenyl-5,5-dialkylimidazolinones

Eighteen substituted 2-phenyl-5,5-dialkylimidazolinones 2 have been prepared by cyclizations of substituted 2-(N-benzoylamino)alkanamides 1. The cyclization of methylamides 1 proceeds at room temperature whereas primary amides are cyclized on boiling. The ¹H and ¹³C nmr spectra of the imidazolinones are presented and the changes in their spectra connected with their protonation in hexadeuteriodimethyl sulfoxide-trifluoroacetic acid mixtures are discussed.     

Perturbation theory for open-shell systems: Simulation of the UHF states by means of the perturbed RHF wave functions

Second-, third-, and selected fourth-order contributions to the correlation energy were calculated for a series of simple open-shell systems by means of the previously developed double-perturbation theory in the restricted MO formalism. It was found possible to assign some of the diagrams to self-consistency effects and to approximate in this way the E – E energy difference. A comparison is made with a more rigorous approach, in which the UHF ground-state wave function is expressed as a first-order perturbation expansion based on the RHF reference wave function. Distinguishing between “self-consistency” and “correlation” diagrams for open-shell systems in the RHF formulation represents a special case of a more general problem met in any double-perturbation treatment, such as, e.g., treatments of systems in the external field or perturbation expansions with noncanonical orbitals.     

Use of x-ray fluorescence spectrometry in ion-exchange studies of leach liquors

Equilibrium and kinetic studies of ion exchange of a complex leach liquor from coal ash, with strongly basic resins and a liquid ion exchanger are reported. The multi-component system was studied by determining the composition of the effluents and by non-destructive analysis of the loaded ion exchangers by XRF spectrometry. In the case of column operation, the elution processes were investigated by the same method, which was very appropriate for non-destructive monitoring of resin regeneration steps done repeatedly with the same resin sample.     

On lower bounds of number of perfect matchings in fullerene graphs

Couting perfect matchings in graphs is a very difficult problem. Some recently developed decomposition techniques allowed us to estimate the lower bound of the number of perfect matchings in certain classes of graphs. By applying these techniques, it will be shown that every fullerene graph with p vertices contains at least p/2+1 perfect matchings. It is a significant improvement over a previously published estimate, which claimed at least three perfect matchings in every fullerene graph. As an interesting chemical consequence, it is noted that every bisubstituted derivative of a fullerene still permits a Kekulé structure.