On distribution of molecular weight in anionic polymerizates of caprolactam

Measurement has been made of the dependence of the molecular weight distribution on the ratio of the catalytic system components and on the polymerization time for polycaprolactam obtained by anionic polymerization. A bimodal character of the curves was observed for products made using molar ratios of activator (N-benzoylcaprolactam) to initiator (sodium dihydro-bis(methoxyethoxy)aluminate) of 1:1 and 1:3, when the polymerization times were less than 1 hr. This course is explained by the influence of fast side-reactions, mainly condensations. For a ratio of 3:1 of the components of the catalytic system, smooth integral distribution curves are obtained, accounting for a very fast decrease in the strong base concentration in the initial stages of the polymerization.     

Application of capillary zone electrophoresis and reversed-phase high-performance liquid chromatography in the biopharmaceutical industry for the quantitative analysis of the monosaccharides released from a highly glycosylated therapeutic protein

Two assays for the quantitative determination of the neutral and amino-monosaccharides attached to a therapeutic glycoprotein were developed using capillary zone electrophoresis (CZE) and RP-HPLC. These assays meet the strict batch release requirements of the quality control in biopharmaceutical industry. The monosaccharides were released from the glycoprotein by hydrolysis with 2N trifluoroacetic acid. In the CZE assay the monosaccharides were reacetylated prior to derivatization with 8-aminopyrenesulfonic acid (APTS), reacetylation in the glycoprotein matrix was investigated in detail. The RP-HPLC method used pre-column derivatization with anthranilic acid in methanol-acetate-borate reaction medium; reacetylation was not necessary. However, epimerization of the different monosaccharides was observed and studied in detail. For the quantitative assay, separation of the amino-monosaccharide epimers had to be developed. The HPLC assay was validated.     

Spectral and electrochemical study of coordination molecules Cu4OX6L4: 3-Methylpyridine and 4-Methylpyridine Cu4OBrnCl(6−n)L4 complexes

The tetranuclear Cu₄OBr_nCl_(6-n)L₄ complexes, where L = 3-methylpyridine (3-Mepy), 4-methylpyridine (4-Mepy) and n=0–6 with trigonal bipyramidal coordination of copper(II) were prepared and their infrared and electronic absorption spectra as well as cyclic voltammograms in nitromethane solutions were measured. The polyhedra in Cu₄OBr_nCl_(6−n) (3-Mepy)₄ molecules are less distorted comparing with those of 4-Mepy analogues as indicated by infrared Cu₄O absorptions, far infrared Cu—Br, Cu—Cl, and Cu—N absorptions, d—d bands in electronic spectra and potentials, measured by cyclic voltammetry. The 3-Mepy complexes exhibit strong single infrared Cu₄O absorptions, while for related 4-Mepy complexes doubly split Cu₄O bands were observed. Two strongly overlapped d—d bands in electronic absorption spectra of the 3-and 4-Mepy complexes in nitromethane were resolved by Gaussian fitting. The 4-Mepy ligand produces slightly stronger ligand field than its 3-Mepy analogue. The maxima of high-energy d—d bands are in a linear correlation with the number of bromide ligands. The correlations for corresponding low-energy bands are considerably deviated from linearity. The halfwave potentials of the complexes in nitromethane correlate with both the number of bromides and the data of electronic absorption spectra suggesting that the reducing electron at the electrode process enters the half-filled d _{z 2} orbital of the copper(II) atom. The origin of a difference between the 3-and 4-Mepy complexes in their spectral and electrochemical properties is also discussed.     

Influence of the pyridine methyl substituent position on the chemical changes of the NCS groups in the thermal decomposition of coordination compounds of the type Cu(NCS)2L2

The influence of the position of the CH₃ group in picoline and lutidine ligands on the degree of chemical change of the NCS groups in coordination compounds of the type Cu(NCS)₂L₂ (whereL=2-, 3- and 4-picoline, and 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-lutidine) is dealt with. The most marked effect of the CH₃ group is found to be exerted in position 4. This effect of the methyl group on the degree of chemical change points to the mutual influence of the ligands in coordination compounds of Cu(II).

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Zusammenfassung Der Artikel befaßt sich mit dem Einfluß der Lage der CH₃ Gruppe in Pikolinen und Lutidinen als Liganden auf den Grad der chemischen Änderungen der Gruppen NSC in Koordinationsverbindungen des Typs Cu(NCS)₂L₂ (L=2-, 3- und 4-Pikoline, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- und 3,5-Lutidine). Der ausgeprägteste Effekt der CH₃ Gruppe wurde in der Position 4 beobachtet. Dieser Einfluß der Methylgruppe auf das Ausmaß der chemischen Änderungen deutet auch auf die gegenseitige Wirkung der Liganden in Koordinationsverbindungen von Cu(II).

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Résumé L'article a trait à l'influence de la position du groupe CH₂ dans les picolines et lutidines, en tant que ligands, sur le degré des changements chimiques des groupes SCN dans les composés de coordination du type Cu(SCN)₂L₂ (L=2-, 3 et 4-picoline, 2,3-, 2,4-,2,5-, 2,6-, 3,4- et 3,6-lutidine). L'effet le plus prononcé du groupe CH₃ s'observe en position 4. Cette influence du groupe méthyle sur le degré des changements chimiques indique aussi l'influence mutuelle des ligands dans les composés de coordination du Cu(II).

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- , , NCS Cu(NCS)₂,L₂, L=2-, 3- 4- , 2.3-, 2.4-, 2.5-, 2.6-, 3.4- 3.5-. , 4. Cu(II).

     

Geometrical structure of yttrium and metal-bromine complexes in solution: limitations of extended X-ray absorption fine structure analysis (EXAFS)

An extensive study on the appearance of multi-electron features in the X-ray absorption spectra of several yttrium(III)-based compounds has been performed. The existence of a multi-electron transition of non-negligible intensity within the extended X-ray absorption fine structure (EXAFS) region of the Y K-edge spectra has been proven. The impact of such features in the EXAFS analysis is made evident for aqueous solutions of YBr3 x 6H2O in liquid and glassy states in the concentration range 0.005-2.0 M, in which this transition induces an overestimation in the coordination numbers derived from EXAFS. We have performed theoretical computation of cross-sections for the double-electron processes at the K-edge of both Y and Br. These computations have been applied to the experimental EXAFS K-edge spectra of both Y and Br in several solids and in aqueous solutions. While in the case of Y K-edge spectra the presence of such multi-electron transitions was seen to seriously affect the standard EXAFS analysis, its influence in the case of Br K-edge spectra was determined to be negligible.     

Sandwich structures at oil-water interfaces under alkaline conditions

Equilibrium liquid crystal (LC) layer on an interface between crude oils and water was observed at high pH. This layer is composed mainly of sodium naphthenates produced in situ at the water/oil interface. Transient LC layer was also evolved at the interface of aqueous phase of sodium hydroxide solutions and oleic phase of naphthenic acid (NA) solutions as result of a chemical reaction between NaOH and NA. This chemical reaction causes transport process resulting in a disturbance of the interface. Optical observation of this interface disturbance reviled that the interface covered with LC shows considerably lower flexibility as compared to LC free interface. The LC layer eventually dissolves in the water phase at low oil-to-water ratio, while at high oil-to-water ratio it can form an equilibrium phase, which spreads spontaneously at the oil-water interface.     

Thermodynamic parameters for the molecular inclusion reaction of dulcin with beta-cyclodextrin. spectrofluorimetric determination of dulcin

The inclusion of dulcin in alpha- and beta-cyclodextrin has been studied by fluorescence spectroscopy. To quantitatively describe complex formation between the beta-cyclodextrin and dulcin, an association constant of 290 M(-1) at 21 degrees was obtained. The thermodynamics associated with the complex formation between dulcin and beta-cyclodextrin in aqueous solution has been studied. The obtained value of DeltaG(0) = -13.7 kJ/mole at 21 degrees , together with DeltaH(0) = -33.6 +/- 2.3 kJ/mole and DeltaS(0) = -67.2 +/-8.3 Jmole(-1) K(-1) indicate that dulcin has a very marked tendency to associate with beta-cyclodextrin in water. The inclusion complex of dulcin in beta-cyclodextrin has been used to determine dulein in the range 0.13-5 mug/ml the method has been applied to determine dulcin in soft drinks.     

Analysis of primary aliphatic short-chain monoamines by LC in water samples

Several derivatization procedures with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) were compared for a rapid analysis of primary aliphatic short-chain monoamines in water samples by HPLC using a LiChorospher analytical separation column (100RP₁₈ mm i.d., 5 μm). Both the solution and the solid-support assisted off-line derivatization on C₁₈ SPE cartridges were inadequate options because of beginning degradation processes of the instable isoindol derivatives during their transfer to the analytical column. This problem was precluded with the on-column or solid-support assisted on-line derivatization. In the last mentioned procedure, the derivatization took place in a Hypersil C₁₈ precolumn ( mm i.d., 30 μm) connected with an additional preconcentration step resulting in better detection limits (0.002-0.040 μg ml⁻¹ requiring only 150 μl of water sample) than in the on-column procedure (0.08-0.16 μg ml⁻¹). The improved sample handling, the better control of parameters affecting reaction rates, the fully automation of this method with only 10 min analysis time for each sample are further advantageous. The potential of the solid-support assisted on-line derivatization was outlined and applied to water samples from several sources. Recovery values near 100% were obtained.     

Properties and analytical applications of the heteropolymolybdates of phosphorus, arsenic, silicon and germanium-IV Determination of phosphomolybdic and silicomolybdic acids via the molybdenum content, with phenylfluorone

Procedures are proposed for the determination of phosphorus and silicon in the ppM range, by extraction of phosphomolybdic and silicomolybdic acids with organic solvent, decomposition of the complex and spectrophotometric determination of its molybdenum content.     

Complex study of nickel skeleton catalysts: V. Study of novel non-pyrophoric nickel skeleton catalysts by derivatograph

The structure and properties of non-pyrophoric skeleton catalysts prepared from NiSi, NiAlSi, NiMg and NiZn alloys have been studied—apart from other thermal methods—by means of the derivatograph.Our experimental results have contributed to the explanation of the non-pyrophoric behaviour of these catalysts. We demonstrated that the desorption of the hydrogen content in our catalysts is not accompanied by the oxidation of active nickel. This oxidation takes place only at higher temperatures, above 200°C, at a rate proportional to the amount of active nickel.Other constituents of the catalysts (adsorbed water, hydroxide content) were also determined from the experimental data. The outstandingly high Mg(OH)₂ content of the NiMg catalyst indicates that its structure is dissimilar: Mg(OH)₂ also acts as support for the catalyst.