JSCS Vol 66, No. 3

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J.Serb.Chem.Soc. 66 (3)139–152(2001)
547.582.2:547.462.3:542.0
JSCS–2841
Original scientific paper

Synthesis and characterization of thermoplastic copolyester elastomers modified with fumaric moieties

VESNA ALEKSANDROVIC and JASNA DJONLAGIC

Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, YU-11000 Belgrade, Yugoslavia

(Received 18 September 2000)
A series of poly(ether-ester)s derived from dimethyl terephthalate (DMT), dimethyl fumarate (DMF), 1,4-butandiol (BD) and poly(tetramethylene oxide) (PTMO,Mn = 1000 g/mol) was synthesized in a two stage process involving transesterification and polycondensation in the melt. The mole ratio of the starting components was selected to result in copolymers with a constant hard:soft segment wieght ratio (56:44). The amount of DMF was 10 mol %, referred to the total amount of the esters used. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate, Ti(OBu)4 and thermal stabilizer N,N’-diphenyl-p-phenylenediamine, DPPD, as well as the temperature. The composition and structure of the synthesized poly(ether-ester)s were characterized by 1H-NMR. The number average molecular weights of the polymers calculated from the 1H-NMR spectra were compared with the corresponding values of the inherent viscosity (hinh) in m-cresol and the complex dynamic viscosity (h *). The effect of the content of fumaric residues on the thermal properties of the synthesized copolyesters was also investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).
Keywords: thermoplastic elastomers, poly(ether-ester)s, fumaric residue, 1H-NMR-spectroscopy.
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J.Serb.Chem.Soc. 66 (3)153–159(2001)
UDC 548.56:547.476.6
JSCS–2842
Original scientific paper

Characterization of polymer-liquid crystal blends

DANIELA FILIP, CRISTOFOR I. SIMIONESCU and DOINA MACOCINSCHI

“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41 A, 6600 Jassy, Romania

(Received 14 August, revised 6 December 2000)
Blends of semi-crystalline polymers (polyethylene adipate and two poly(ester-urethane) s) with liquid crystal cholesteryl palmitate with different compositions were prepared by solution casting. One of the poly(ester-urethane)s was based on 2,4-tolylene diisocyanate (TDI) and the other one on 4,4’-diphenylmethane diisocyanate (MDI). The miscibility and phase transition were investigated over the whole range of concentration by differential scanning calorimetry and polarizing optical microscopy.
Keywords: liquid crystal, blend, polyester, poly(ester-urethane).
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J.Serb.Chem Soc. 66(3)161–172(2001)
UDC 547.551/.1:541.51
JSCS–2843
Original scientific paper

Gaseous-phase proton affinity of anilines: A quantum chemical evaluation and discussion in view of aqueous basicity

ALEXEI N. PANKRATOV, INNA M. UCHAEVA, SERGEI YU. DORONIN and RIMMA K. CHERNOVA

Department of Chemistry, N. G. Chernyshevskii Saratov State University, 83 Astrakhanskaya Street, Saratov 410026, Russia

(Received 15 September, revised 4 December 2000)
Using the PM3 method, enthalpies and free energies of the gaseous-phase proton affinity (PA) have been computed for aniline and 62 of its derivatives with different kinds of electron-donor and electron-acceptor substitution in the aromatic ring and at the nitrogen atom. Linear correlations of the type pKavs. PA have been found. Deviations of the data for ortho substituted anilines from the above relationships was discussed in view of possible hydrophobic hydration of the molecular fragments ajacent to the protonation centre. Linear dependeces Pexpar = bPtheor (where P is standard entropy, heat or Gibbs energy of formation, first ionization potential, molecular dipole moment) were found.
Keywords: anilines, proton affinity, basicity, quantum chemical computation, theory-experiment correlation, hydrophobic hydration.
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J.Serb.Chem.Soc. 66(3)173–178(2001)
UDC 543.54:547.49
JSCS–2844
Original scientific paper

Application of the Log k pair linearity rule and Proportionality rule to the RPP mobile phase scales estimation on cyano-silica column

TOMISLAV J. JANJIC, GORDANA VUCKOVIC and MILENKO B. CELAP

Faculty of Chemistry, University of Belgrade, P. O. Box 158, YU-11001 Belgrade, Yugoslavia

(Received 13 November 2000)
On the basis of literature-reported log k values, the Log k pair linearity rule and the Proportionality rule were found to be also valid in the case of cyano-silica sorbent, whenmethanol, acetonitrile or propane-2-olwere used as modifiers. The RPP scales, reflecting the solvent strength, are in good linear relationship with the experimentally determined log k values. Furthermore, in the case of methanol and acetonitrile, the linear dependence: log k = f (mol% of modifier) was also established. In the function obtained in a such way, the intercept and the slope exhibit an approximate linear dependence. Finally, in the case of methanol, the experimentally obtained log k values are in a satisfactory agreement with the values calculated by the above equation.
Keywords: column chromatography, cyano-silica sorbent, Log k pair linearity rule, Proportionality rule, RPP scale.
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J.Serb.Chem.Soc. 66(3)179–188(2001)
UDC 546.273/546.26:543.257.1
JSCS–2845
Original scientific paper

Potentiometric application of boron- and phosphorus-doped glassy carbon electrodes

BILJANA F. ABRAMOVIC, VALÉRIA J. GUZSVÁNY, FERENC F. GAÁL and ZORAN V. LAUSEVIC*

Institute of Chemistry, Faculty of Science, Trg D. Obradovica 3, YU-21000 Novi Sad and
*Vinca Institute of Nuclear Science, P. O. Box 522, YU-11001 Belgrade, Yugoslavia

(Received 19 September, revised 5 December 2000)
Acomparative study was carried out of the potentiometric application of boronand phosphorus-doped and undoped glassy carbon samples prepared at the same heat treatment temperature (HTT 1000°C). The electrochemical activities of the obtained electrode materials were investigated on the example of argentometric titrations. It was found that the electrochemical behaviour of the doped glassy carbon samples are very similar to a Sigri (undoped) glassy carbon sample (HTT 2400°C). The experiments showed that the potentiometric response depends on the polarization mode, the nature of the sample, the pretreatment of the electrode surface, and the nature of the supporting electrolyte. The amounts of iodide, bromide, and of chloridewere determined to be 1.27 mg, 0.80 mg and 0.54 mg, respectively, with a maximum relative standard deviation of less than 1.1%. The obtained results are in good agreement with the results of comparative potentiometric titrations using a silver indicator electrode. The titrationmethod was applied to the indirect determination of pyridoxine hydrochloride, i.e., vitamin B6.
Keywords: boron- and phosphorus-doped glassy carbon electrodes; potentiometric titration of halides; determination of vitamin B6.
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J.Serb.Chem.Soc. 66(3)189–198(2001)
UDC 648.75
JSCS–2846
Original scientific paper

The application of Near Infrared Reflectance Spectroscopy (NIRS) for the quantitative analysis of hydrocortisone in primary materials

K. NIKOLICH, C. SERGIDES and A. PITTAS

Medochemie Ltd, Limassol, Cyprus

(Received 15 May, revised 5 December 2000)
Near Infrared Reflectance Spectroscopy (NIRS), coupled with fiber optic probes, has been shown to be a quick and reliable analytical tool for quality assurance and quality control in the pharmaceutical industry, both for verifications of raw materials and quantification of the active ingredients in final products. In this paper, a typical pharmaceutical product, hydrocortisone sodium succinate, is used as an example for the application of NIR spectroscopy for quality control. In order to develop an NIRS method with higher precision and accuracy than the official UV/VIS spectroscopic method (BP '99), 19 samples, taken from one year’s production and several prepared in the laboratory, having a hydrocortisone sodium succinate concentration in the range from 89.05%to 95.83 %, were analysed by NIR and UV/VIS spectroscopy. Three frequency ranges: 5939.73–5627.32 cm-1; 4863.64 – 4574.36 cm-1; 4308.23–4200.24 cm-1, with the best positive correlation between the changes in the spectral and concentration data, were chosen. The validity of the developed NIRS chemometric method for the determination of the hydrocortisone sodium succinate concentration, constructed by the partial least squares (PLS) regression technique, is discussed. A correlation coefficient of 0.9758 and a standard error of cross validation (RMSECV)of 1.06%were found between the UV/VI Sand ňhe NIR spectroscopic results of the hydrocortisone sodium succinate concentration in the samples.
Keywords: FTNIRS, quantitative analysis, hydrocortisone.
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J.Serb.Chem.Soc. 66(3)199–204(2001)
UDC 632.95
JSCS–2847
Original scientific paper

Development and optimization of a method for the determination of simazine, atrazine and propazine using solid-phase extraction and HPLC/GC

VERA TRAJKOVSKA, SIMKA PETROVSKA-JOVANOVIC and MIRKO CVETKOVSKI*

Institute of Chemistry, Faculty of Science, "St. Cyril and Methodius University", P.O. Box 162, 91000 Skopje, Macedonia and
*Republic Institute of Hydrometeorology, Skupi bb, 91000 Skopje, Macedonia

(Received 18 May, revised 25 December 2000)
Asolid-phase extraction (SPE) method, coupled with HPLC/DAD and GC/FID analysis has been developed for the simultaneous determination of simazine, atrazine and propazine in water samples. The compounds of interest were enriched on Envi-carb SPE tubes. The recoveries for simazine, atrazine and propazine from spiked Nanopure water were 101±5.6 %, 99±4.9 % and 96±5.7 %, respectively. The detection limits were 4.00, 8.00 and 10.00 ng absolute samplemass in the column for simazine, atrazine and propazine, respectively. Standard curve r2 values of 0.9828–0.9988 for the analyzed compounds were consistently obtained.
Keywords: determination, solid-phase extraction, HPLC/GC, atrazine, simazine, propazine.
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J.Serb.Chem.Soc. 66(3)205–211(2001)
UDC 577.16/612.015.6
JSCS–2848
Original scientific paper
 Kinetic determination of rutin

S. S. MITIC, J. I. VUCETIC*, S. M. MILETIC and D. A. KOSTIC

Department of Chemistry, University of Nis, Cirila i Metodija 2, YU-18000 Nis, and
*Faculty of Chemistry, University of Belgrade, YU-11000 Belgrade, Yugoslavia

(Received 18 October, revised 18 December 2000)
Akinetic method is described for the determination of rutin based on its inhibitory effect on the Fe(II)-AA catalysis of the oxidation of C6H5COONa with hydrogen peroxide. Detection limit of this method is 0.16 ng cm-3. The relative error ranges between 0.9 to 9.8%for the concentration interval 0.82 ng cm-3 to 8.2 ng cm-3. Kinetic equations are proposed for the investigated process. The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method.
Keywords: kinetic method, rutin, determination.
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