JSCS Vol 71, No. 11

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J. Serb. Chem. Soc. 71 (11) 1125–1135 (2006)
UDC 547.53.024+547.861.3:612
doi: 10.2298/JSC0611125Z
JSCS – 3506
Original scientific paper

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Influence of N–1 substituent properties on binding affinities of arylpiperazines to the binding site of 5-HT1A receptor


Faculty of Chemistry, University of Belgrade, POB 158, 11000 Belgrade, Serbia
*ICTM, Department of Chemistry, University of Belgrade, POB 473, 11000 Belgrade, Serbia

(Received 19 May, revised 24 July 2006)

Serotonin receptors (5-HTRs), especially the 5-HT1A subtype, have been the subject of intensive research for the past decade, due to their function in human physiology. Several structurally different classes of ligands are known to bind to the 5-HT1A receptor, but arylpiperazine derivatives are AMong the most important ligands. In the work, docking analyses were used to explain the binding affinities of a series of ligands with different N-1 substituent. All ligands had in common the arylpiperazine structure, while the N-1 substituent was modified to investigate the influence of ligand structure on its binding affinity. The shape and size, as well as the rigidity of the substituents were altered to investigate the possible effects on the formation of the receptor – ligand complex.

Keywords: 5-HT1A, binding site, hydrophobic pocket, arylpiperazine.

J. Serb. Chem. Soc. 71 (11) 1137–1145 (2006)
UDC 546.32'273+546.712'722'732'742'562+547.821:543.42
doi: 10.2298/JSC0611137S
JSCS – 3507
Original scientific paper

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Synthesis, characterization and spectroscopic studies of the dihydrobis(1,2,3-benzotriazolyl)borate anion and its complexes with MCl2·py2


Department of Chemistry, Aligarh Muslim University, Aligarh-202002, India

(Received 18 May 2005, revised 14 May 2006)

The preparation of sodium dihydrobis(1,2,3-benzotriazolyl)borate was realised by refluxing one mole of sodium borohydride with two moles of 1,2,3-benzotriazole in toluene over a period of 12 h. Its complexes with MCl2·py2 [whereM=Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and py=pyridine] were characterized by elemental analysis as well as magnetic, spectroscopic and conductivity measurements. On the basis of these studies, it is proposed that the geometry of all the complexes is octahedral. The ligand field parAMeters 10 Dq, B and b show extensive overlap between the M–L orbital. The molar conductance of 10-3 M solutions of the complexes in DMSO suggest them to be non-ionic in nature.

Keywords: borate, transition metal complexes, spectroscopy.

J. Serb. Chem. Soc. 71 (11) 1147–1151 (2006)
UDC 546.43+547.545+546.212:66.022.362
doi: 10.2298/JSC0611147M
JSCS – 3508
Short communication

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Short communication
Stability of the barium–benzo-15-crown-5 complex in nitrobenzene saturated with water


Faculty of Applied Sciences, University of West Bohemia, Husova 11, 306 14 Pilsen, Czech Republic
*Prague Institute of Chemical Technology, Technická 5, 166 28 Prague 6, Czech Republic

(Received 20 July 2005, revised 21 March 2006)

From extraction experiments and g-activity measurements, the exchange extraction constant corresponding to the equilibrium Ba2+(aq) + SrL22+(nb) D BaL22+(nb) + Sr2+(aq) occurring in the two-phase water–nitrobenzene system (L =benzo-15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (Ba2+, SrL22+) = 0.3 ± 0.1. Furthermore, the stability constant of the benzo-15-crown-5–barium complex in nitrobenzene saturated with water was calculated for the temperature of 25 °C: log bnb (BaL22+)=13.3±0.1.

Keywords: barium, benzo-15-crown-5, stability constant, nitrobenzene.

J. Serb. Chem. Soc. 71 (11) 1153–1160 (2006)
UDC 661.53+661.56:66.097.3+547.314.2:66.094.25
 doi: 10.2298/JSC0611153H

JSCS – 3509
Original scientific paper

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A study concerning the pretreatment of CNTs and its influence on the performance of NiB/CNTs AMorphous catalyst


*Department of Chemistry, Nanchang University, Nanchang, Jiangxi 330047, P.R. China

**Jiangxi Key Laboratory of Nationals Surface Engineering, Jiangxi Science and Technology Normal University, P.O. Box 224, Nanchang 330013, P.R. China

(Received 17 October 2005, revised 6 March 2006)

As prepared carbon nanotubes were pretreated with nitric acid (CNTs-HNO3) or AMmonia (CNTs-NH3). Fourier transform infrared spectroscopy (FTIR) measurements showed that the surface of the nanotubes was functionalized with carboxylic and hydroxyl functional groups after the acid treatment and that basic groups containing nitrogen, such as N–H and C–N, were introduced to the surface of the nanotubes after the AMmonia treatment. X-Ray diffraction analysis implied that the nickel residue in the CNTs was effectively removed by acid treatment. However, the nickel residue was only partially eliminated by AMmonia pretreatment. NiB AMorphous catalysts supported on CNTs-HNO3 and CNTs-NH3 were prepared by the impregnation–chemical reduction method and characterized by transmission electron microscopy (TEM), as well as inductively coupled plasma (ICP) spectroscopy and studied in the selective hydrogenation of acetylene. TEM measurements showed that a high density NiB particles of about 9 nm were homogeneously dispersed on the CNTs-NH3. However, NiB particles (13–23 nm)with AMean size of 16 nm were scattered on the CNTs-HNO3. As a result, the activity and selectivity of NiB/CNTs-NH3 were higher than those of NiB/CNTs-HNO3 in the selective hydrogenation of acetylene.


Keywords: CNTs, pretreatment, NiB AMorphous catalyst, acetylene selective hydrogenation, AMmonia.

J. Serb. Chem. Soc. 71 (11) 1161–1172 (2006)
UDC 549.67:541.132.3:621.5.013+547.233
doi: 10.2298/JSC0611161L
JSCS – 3510
Original scientific paper

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Surface modification of a zeolite and the influence of pH and ionic strength on the desorption of an AMine


Institute for Technology of Nuclear and Other Mineral Raw Materials, P. O. Box 390, 11001 Belgrade, Serbia
Veterinary Specialized Institute, P. O. Box 390, 36000 Kraljevo, Serbia

(Received 31 October 2005, revised 16 February 2006)
The adsorption of stearyldimethylbenzylAMmonium chloride (SDBAC) on the clinoptilolite–heulandite rich tuff in dependence on the applied temperature was studied. The maximal AMount of sorbed SDBAC was 123 mmol/kg in the case of thermally treated zeolite tuff (100 °C) and a warm surfactant solution (80 °C). The AMount and properties of water adsorbed on the organo-zeolite (OZ) as well as the bonding between the organic species and the zeolite were investigated by DTA, TG, DTG and IR analyses. During gradual heating in an oxidizing atmosphere, the adsorbed organic material was oxidized, giving rise to significant exothermic peaks. The adsorption of water vapor decreased with increasing SDBAC loading up to 75 mmol/kg of zeolite, which can be ascribed to an intensification of the hydrophobic characteristics of the surface. With loadings above the 75 mmol/kg, the adsorption of water vapor increased. Desorption of SDBAC from the organo-zeolite under environmentally relevant conditions: distilled water, pH 3 and 10 buffers, as well as aqueous NaCl and CaCl2 solutions, was investigated. OZs with loadings up to their external cation exchange capacity value (75 mmol/kg) were stable under all of the applied conditions.

Keywords: organo-zeolite, quaternary AMine, surface modification, ion exchange.

J. Serb. Chem. Soc. 71 (11) 1173–1186 (2006)
UDC 621.3.032.22+546.62+546.96–31:546.226–325:546.33.131
doi: 10.2298/JSC0611173P
JSCS – 3511
Original scientific paper

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Activity and stability of RuO2-coated titanium anodes prepared via the alkoxide route


ICTM-IEC, Njegoseva 12, 11000 Belgrade, Serbia
*Vinca Institute of Nuclear Sciences, P. O. Box 522, 11001 Belgrade, Serbia
**Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, P. O. Box 3503, YU-11120, Belgrade, Serbia

(Received 12 May, revised 24 July 2006)
Titanium anodes with an active RuO2 coating of two different thicknesses were prepared from the oxide suspended in ethanol ("ink" method), while the oxide itself was synthesized by the hydrolysis of ruthenium ethoxide in an ethanolic solution (alkoxide route). The morphology of prepared oxide was exAMined by scanning electron microscopy. The electrochemical properties of the prepared Ti/RuO2 anodes, involving their cyclic voltAMmetric behavior in H2SO4 and NaCl solutions, activity in the chlorine and oxygen evolution reaction, impedance behavior in H2SO4, and stability during electrolysis in dilute chloride solutions, were investigated. The performances of the anodes are compared to those of a Ti/RuO2 anode prepared by the sol–gel procedure from an oxide sol obtained by the forced hydrolysis of ruthenium chloride in acid solution. The anodes prepared via the alkoxide route showed a higher capacitance and activity for the chlorine evolution reaction than the anode prepared by the inorganic sol–gel procedure. The results of the stability test showed that the utilization of the coating active material is better when the anodes were prepared via the alkoxide route than via the inorganic sol–gel procedure, particularly for anodes with a smallermass of coating. The different rates of loss of activity indicate a degradation mechanism for the anodes prepared via the alkoxide route in which electrochemical dissolution of RuO2 from the coating surface prevails over the growth of an insulating TiO2 layer in the coating/Ti substrate interphase. The effect of RuO2 dissolution from the coating surface increases with increasing coating mass.

Keywords: RuO2 coating, alkoxide, ink method, ruthenium ethoxide, chlorine evolution, anode stability.

J. Serb. Chem. Soc. 71 (11) 1187–1194 (2006)
UDC 54–71'131:546.76:620.193:546.226–325
doi: 10.2298/JSC0611187J
JSCS – 3512
Preliminary communication

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Influence of chloride ions on the open circuit potentials of chromium in deaerated sulfuric acid solutions


Institute for Chemical Power Sources, Batajni~ki drum bb, 11070 Belgrade-Zemun, Serbia
*Institute of Chemistry, Technology and Metallurgy-Center for Electrochemistry, P. O. Box 473, 11001 Belgrade, Serbia

(Received 20 October 2005, revised 13 January 2006)
Open circuit potential measurements and cyclic voltAMmetry of chromium in deaerated aqueous H2SO4 solution of pH 1 without and containing NaCl in the concentration range 0.5 – 4 M revealed that chromium exhibits two stable open circuit potentials having the character of a Wagner–Traud corrosion potential. One, Ecorr.1, was established on the passive surface formed by exposing Cr previously to air or passivated potentiostacially in a controlled manner, and the second one, Ecorr.2, at the bare Cr surface obtained by prolonged cathodic activation. There is a small difference in the Ecorr.1 values as a function of the passive layer properties. Addition of NaCl accelerates the hydrogen evolution reaction on the passive surface to some extent, while the sAMe reaction on the bare surface was not affected by NaCl. On the other hand, presence of NaCl accelerates the anodic reaction on the bare surface, and it activates the dissolution of the passive layer so that the passive currents increase with addition of NaCl. This effect is so large that at concentration of NaCl larger than 3 M, the destruction of the passive layer was so fast that in a matter of seconds the Cr was activated, and the only one stable corrosion potential observed was Ecorr.2. No pitting of Cr in the presence of NaCl was observed up to the transpassive potentials.

Keywords: chromium, corrosion, open circuit potential, sulfuric acid, chloride ions.

J. Serb. Chem. Soc. 71 (11) 1195–1205 (2006)
UDC *Eletriptan+*UK 120.413:543:615.2/3:577.2/3:577.2
doi: 10.2298/JSC0611195Z
JSCS – 3513
Original scientific paper

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Validation of an HPLC method for the simultaneous determination of eletriptan and UK 120.413


Institute of Pharmaceutical Chemistry and Drug Analysis, Faculty of Pharmacy, Vojvode Stepe 450, P. O. Box 146, 11000 Belgrade, Serbia
*Pharmacy M315, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, W. A., 6009, Australia

(Received 2 December 2005)

Arapid and sensitive RPHPLCmethod was developed for the routine control analysis of eletriptan hydrobromide and its organic impurity UK 120.413 in Relpax® tablets. The chromatography was performed at 20 °Cusing a C18 XTerraTM (5 m, 150 × 4,6 mm) column at a flow rate 1.0 ml/min. The drug and its impurity were detected at 225 nm. The mobile phase consisted of TEA (1 %) – methanol (67.2:32.8 v/v), the pH of which was adjusted to 6.8 with 85 % orthophosphoric acid. Quantification was accomplished by the internal standard method. The developed RP HPLC method was validated by testing: accuracy, precision, repeatibility, specificity, detection limit, quantification limit, linearity, robustness and sensitivity. High linearity of the analytical procedure was confirmed over the concentration range of 0.05 – 1.00 mg/ml for eletriptan hydrobromide and from 0.10 – 1.50 µg/ml for UK 120.413, with correlation coefficients greater than r = 0.995. The low value of the RSD expressed the good repeatability and precision of the method. Experimental design and a response surface method were used to test robustness of the analytical procedure and to evaluate the effect of variation of the method parAMeters, nAMely the mobile phase composition, pH and temperature. They showed small deviations from the method setting. The good recovery and low RSD confirm the suitability of the proposed RP HPLC method for the routine determination of eletriptan hydrobromide and its impurity UK 120.413 in Relpax® tables.

Keywords: validation, RP HPLC, eletriptan hydrobromide, UK 120.413.

J. Serb. Chem. Soc. 71 (11) 1207–1218 (2006)
UDC 510.644:615.212:543.42
doi: 10.2298/JSC0611207S
JSCS – 3514
Original scientific paper

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Principal component articial neural network calibration models for the simultaneous spectrophotometric estimation of
mefenAMic acid and paracetAMol in tablets


Department of Pharmacy, AnnAMalai University, AnnAMalainagar, TAMil Nadu – 60802, India

(Received 8 August 2005, revised 3 February 2006)

Simultaneous estimation of all drug components in a multicomponent analgesic dosage form with artificial neural networks calibration models using UV spectrophotometry is reported as a simple alternative to using separate models for each component. Anovel approach for calibration using a compund spectral dataset derived from three spectra of each component is described. The spectra of mefenAMic acid and paracetAMol were recorded as several concentrations within their linear range and used to compute a calibration mixture between the wavelengths 220 to 340 nm. Neural networks trained by a Levenberg–Marquardt algorithm were used for building and optimizing the calibration models using MATALAB® Neural Network Toolbox and were compared with the principal component regression model. The calibration models were throughly evaluated at several concentration levels using 104 spectra obtained for 52 synthetic binary mixtures prepared using orthogonal designs. The optimized model showed sufficient robustness even when the calibration sets were constructed from a different set of pure spectra of the components. The simultaneous prediction of both components by a single neural netwook with the suggested calibration approach was successful. The model could accurately estimate the drugs, with satisfactory precision and accuracy, in tablet dosage with no interference from excipients as indicated by the results of a recovery study.

Keywords: artificial neural networks, principal components, UVspectrophotometry, mefenAMic acid, paracetAMol.

J. Serb. Chem. Soc. 71 (11) 1219–1236 (2006)
UDC 631.4+546.18:543.632.47
doi: 10.2298/JSC0611219T
JSCS – 3515
Original scientific paper

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The chemical characteristics of soil which determine phosphorus partitioning in highly calcareous soils


Biotechnical Institute, University of Montenegro, Kralja Nikole b.b., 81000 Podgorica, Montenegro

*Faculty of Chemistry, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia
**Center for Chemistry, Institute for Chemistry, Technology and Metallurgy , ICTM, Njegoseva 12, 11000 Belgrade, Serbia

(Received 12 December 2005, revised 26 February 2006)

Phosphorus fractions from three highly calcareous soils (average, 24.9 ± 4.8 %CO32-) from sAMpling sites with aMediterranean climate were isolated by sequential extraction. In order to provide a more reliable basis for the definition of the obtained P-fractions, principal component analysis was applied and from the chemical characteristics of the 14 investigated soils, those characteristics which define the content and association features of the P-fractions were assessed. The soils are characterized by a relatively high pH (8.0 – 8.2) and by significantly differing contents of organic mater, acid-soluble Mg and total P. These differences affected the various association features of the P-fraction with the soil constituents. The NH4F–P fraction (isolated with 0.5 M NH4F, pH 8.2) is defined by the contents of the main metals of the oxide–hydroxide–clay associations (Al, Fe,Mn) or by the the redox potential (Eh) of Mn. The accumulation of NaOH–phosphorus (extractable with 0.1M NaOH) depended on the constituents of the oxide–hydroxide–clay association, the humic substances and Eh-related factors. In those soils in whichNaOH–Pis defined by the oxide–hydroxide–clay assoiation, the participation of Fe as a bridge-forming metal is proposed. The main part of total P, i.e., DP = TP – (NH4F–P + NaOH–P) is defined by the status of Mn– and Fe–humic complexes or by the concentration of hydroxyl-ions.

Keywords: NH4F–extractable P, NaOH–extractable P, phosphorus-associations, principal component analysis.

J. Serb. Chem. Soc. 71 (11) 1237–1246 (2006)
UDC 661.
doi: 10.2298/JSC0611237R
JSCS – 3516
Extended Abstract

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The sorption and crystallographic characteristics of alumina activated in a reactor for pneumatic transport


ICTM-Department of Catalysis and Chemical Engineering, Njegoseva 12, Belgrade, Serbia
*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia

**Faculty of Mining and Geology, University of Belgrade, Djusina 7, Belgrade, Serbia

(Received 20 October 2005, revised 3 March 2006)

Active transition alumina powders were obtained by flash calcination of gibbsite in a reactor for pneumatic transport in the dilute, two-phase flow regime in the temperature interval from 883 to 943 K with a residence time between 0.4 and 0.9 s. The results of X-ray diffraction analysis confirmed that the activated alumina sAMples were either microcrystalline or AMorphous. From nitrogen adsorption–desorption isotherms, the specific surface areas of all sAMples were calculated by the BETmethod. Using the sorption data, the fractal dimension of the surface of the alumina sAMples was calculated according to a modified FHH method. By application of fractal geometry, using the values of the fractal dimension of the surface and of the specific surface area, the effective surface areas of the active aluminas were calculated for the adsorption of molecules having a cross-section area greater than that of the nitrogen molecule

Keywords: pneumatic transport, transition AMorphous aluminas, X-ray diffraction, fractal dimension.

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