Modification of solids with volatile organics III: Natural zeolites

Summary The effect of pre-adsorbed benzene and ethanol on the adsorptive properties of natural zeolite (clinoptilolite) has been studied by gas-solid chromatography. It has been shown that modification of the solid surface by volatile organics has a significant influence on the adsorptive properties. The modification is of the same order as the more difficult modification by inorganics, as illustrated here by clinoptilolite modification with Co²⁺. Energy distribution of surface adsorptive sites appears to be continuous and confirms previous finding that only a small proportion of active sites is responsible for most adsorbate retention. Part II reference [4]     

Hyaluronic acid-copper(II) complexes: Spectroscopic characterization

Hyaluronic acid-copper(II) complexes were studied by ultraviolet and electron spin resonance spectroscopy (ESR), as well as by rheological measurements. Spin-Hamiltonian parameters were obtained from experimental spectra measured at 200 K by non-linear optimization method. These showg _x g _y <g _z and indicate the ground electronic state of copper ion, which is characteristic for carboxylato-copper(II) complexes. The non-axial symmetry of theg-tensor suggest rhombic crystal field symmetry. Formation of HA-Cu(II) complex is realized through the interaction of copper ions with carboxyl groups of the HA macromolecule. This complex is characteristic of the network-like rheological properties of its aqueous solution.     

Flow injection analysis for calcium in serum,water and waste waters by spectrophotometry and by ion-selective electrode

The Flow Injection technique is shown to provide fast, reliable and sensitive methods for the determination of calcium in various aqueous as well as serum samples; spectrophotometric or potentiometric detection can be used. At sampling rates of 100–110 samples per hour, with 30-μl sample injections, high reproducibility of measurement and low reagent consumption are achieved in both methods. In the spectrophotometric method, the analytical readout is available within 12 s after sample injection at a total reagent consumption of 0.75 ml per analysis. The potentiometric measurement of the calcium activity in serum is placed on a reliable basis by alternating measurements of serum samples and aqueous standards without incurring any non-reproducible changes in potential between aqueous and serum solutions. This permits the simultaneous determination of pH and pCa, the analytical readout being available within XXX s of sample injection. The good agreement between the results obtained with the Flow Injection method and those attained by atomic absorption and EDTA titrations as well as pCa stat-measurements show that the new methods are potentially suitable for routine analysis.     

Hybridization in some macrocyclic polyacetylenes

The hybridization in several cyclic polyacetylene compounds has been calculated by the maximum overlap method, assuming planar and non-planar geometries of the molecules. In the planar configuration the hybrids describing the molecular skeleton deviate from the corresponding bond directions. We have a few “bent” bonds, but in contrast to the situation in small rings, here the deviation angles are negative, i.e., the hybrids point toward the inside of the ring. Non-planar structures in which acetylene groups are kept in a plane and CCH₂ or CH₂ groups are displaced out of the plane show less deviation from the bond directions of bent bonds. Furthermore, the deviation angles decrease with an increase in the out-of-plane displacement of methylene groups. Finally, when the angle of bending of the molecules approaches 50°, the deviation vanishes, predicting a puckered conformation for the molecules. Correlation between CC stretching vibration frequencies and the corresponding CC bond overlap is discussed.     

Papierchromatographische Trennung und Identifizierung der Polyäthylenglykole und ihrer Monoäther

Zusammenfassung Es wurde eine chromatographische Methode zur Auftrennung und Identifizierung der Polyäthylenglykole und ihrer Monoäther nach Über-führung in die Ester der 3,5-Dinitrobenzoesäure ausgearbeitet. Es wurden entweder Lösungsmittelsysteme mit Dimethylformamid oder Formamid als stationäre und Hexan, Cyklohexan, Benzol, Chloroform und ihre Gemische als mobile Phase oder mit Paraffinöl imprägnierte Papiere und das Gemisch Dimethylformamid—Methylalkohol—Wasser als mobile Phase angewendet.

---

Summary A Chromatographic method has been developed for the separation and identification of the polyethylene glycols and their mono-ethers after conversion into the esters of 3,5-dinitrobenzoic acid. The solvent systems employed consisted of dimethylformamide or formamide as stationary phase and hexane, cyclohexane, benzene, chloroform and their mixtures as mobile phase, or papers impregnated with paraffin oil and the mixture of dimethyl-formamide-methyl alcohol were used as the mobile phase.

---

Résumé On a élaboré une méthode chromatographique de séparation et d'identification des polyéthylèneglycols et de leurs monoéthers après leur transformation en ester de l'acide dinitro-3,5 benzoïque. On a employé soit les systèmes de solvants avec le diméthylformamide ou le formamide comme phase stationnaire, et l'hexane, le cyclohexane, le benzène, le chloroforme et leurs mélanges comme phase mobile, ou des papiers imprégnés d'huile de paraffine et le mélange diméthylformamide-alcool méthylique-eau comme phase mobile.

---

---

Herrn Dipl.-Ing.J. Kami aus unserem Institut danken wir für die Darstellung und Reinigung einiger angewandter Verbindungen.     

Effect of selenium oxidation state on cadmium translocation in chamomile plants

Syntheses and spectral characteristics of cadmium(II) compounds (CdSeO₄, CdSeO₃, and Cd(NCSe)₂(nia)₂) containing selenium in oxidation states (VI), (IV), and (-II) are described. In Cd(NCSe)₂(nia)₂, nicotinamide (nia) and selenocyanate anions are bonded to Cd atom as N-donor monodentate ligands. Nicotinamide is coordinated through the ring nitrogen atom. The effects of these selenium compounds as well as Cd(NCS)₂(nia)₂ on the growth and Cd accumulation in roots and shoots of hydroponically cultivated chamomile plants (cultivar Lutea) were studied. In the applied concentration range (12–60 μmol dm⁻³) Cd(NCS)₂(nia)₂ affected neither the length nor the dry mass of roots and shoots. Other compounds applied at 24 μmol dm⁻³ and 60 μmol dm⁻³ significantly reduced dry mass of roots and shoots. Selenium oxidation state in the cadmium compounds affected Cd accumulation in plant organs as well as Cd translocation within the plants, which was reflected in the values of bioaccumulation (BAF) and translocation factors (S/R). Cd amount accumulated by shoots was lower than that in the roots. The highest BAF values determined for Cd accumulation in shoots were obtained with CdSeO₄. Substitution of S with Se in the Cd(NCX)₂(nia)₂ (X = Se or S) caused an increase of Cd translocation into the shoots. Presented at the XVIIIth Slovak Spectroscopic Conference, Spišská Nová Ves, 15–18 October 2006.     

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.     

Charge transfer across a polymer gel/liquid interface: determination of ionophores

An electrochemical method for the determination of the ionophores monensin and lasalocid was developed, based on the polarization of an agar gel/nitrobenzene electrolyte interface. The measured current corresponding to the facilitated ion transfer across this interface is directly proportional to the concentration of an ionophore dissolved in the organic phase. Using cyclic voltammetry in a three-electrode system the detection limit for both ionophores is about 3 × 10^?5 M.     

钼体系催化丁二烯聚合动力学——链转移

本文考察了MoCl_4OC_8H_(17)-(i-Bu)_2Alo催化体系在加氢汽油中催化丁二烯聚合过程中的链转移情况,提出了比较聚合体系中各组分对链转移的贡献大小的方法和计算链转移次数的公式及链转移次数与聚合温度的函数关系式。发现本体系中单体和主催化剂是主要的链转移剂,向烷基铝的链转移占10％,向杂质的链转移仅占6％。在链转移反应中,单体和主催化剂的级数为1,烷基铝的级数为1/2。     

Investigation of isothermal bulk polymerization ofo-alkyaryl methacrylates by DSC

The kinetics of the AIBN-initiated free radical bulk polymerization of fiveo-alkylphenyl methacrylates was studied by means of DSC in the temperature range 353–373 K, and the enthalpy of polymerization, the overall reaction rate constant and the activation energy were determined. The results were compared with those published recently on correspondingp-alkylaryl methacrylates. All measured reaction rate constants were found to increase with increasing temperature and to decrease with increasingo-alkyl substituent mass and size. It was shown thato-substituents influence the rates of polymerization to a greater extent thanp-substituents. At about 373 K, all differences in rate, most probably resulting from steric hindrance caused by the alkyl groups, disappear in both series, a phenomenon earlier observed for dimethyl phenyl methacrylates.This work was supported by the Ministry of Science of the Republic of Serbia.