JSCS Vol 68, No. 8-9
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J.Serb.Chem.Soc.
68 (8–9)599–605(2003) |
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Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the
Balkan peninsula
ANDREAS GEORGAKOPOULOS
School of Geology,
Department of Mineralogy-Petrology-Economic Geology,
Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece (E-mail:
ageorgak@geo.auth.gr)
(Received 3 March 2003)
The cross-polarized magic-angle-spinning NMR (CPMAS-NMR) technique was used in
this work to assess the carbon distribution in coals of different rank (peat,
lignite, xylite, sub-bituminous coal) from important deposits in Greece and
Bulgaria. The technique is assumed to be only semiquantitative, due to a number
of interferences, such as spinning side bands (SSB) in the spectra,
parAMagnetic species in the sAMples, and low or remote protonation of aromatic
carbons. The Bulgarian sub-bituminous coal shows the greatest AMounts of
aromatic structures. The lignite sAMple from the DrAMa basin, Northern Greece,
is relatively unaltered and largely unweathered, and shows the greatest AMounts
of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from
endemic areas in Serbia and Montenegro and Bosnia, taken from published papers,
show significantly more intense resonances for methoxyl, phenolic, and
polysaccharide moieties compared to the DrAMa lignite NMR spectrum. Xylite
reveals high contents of carbohydrates.
Keywords: Balkan endemic nephropathy, 13C CPMAS-NMR, Greece,
lignite, peat, sub-bituminous coal, xylite.
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J.Serb.Chem.Soc.
68(8–9)607–613(2003) |
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Synthesis and characterization of ether linkage
containing bis-fluoran compounds
RITESH G. PATEL, JIGNESH V. PATEL, MANISH P. PATEL and RANJAN G. PATEL
Department of Chemistry,
Sardar Patel University, Vallabh Vidyanagar-388 120, Gujarat, India
(Received 8 January,
revised 28 March 2003)
2’-Chloro-6’-diethylAMinofluoran and 2’-chloro-3’-methyl-6’-diethylAMinofluoran
were reacted with various diphenols in dimethyl formAMide in the presence of
potassium carbonate to give the related bis-fluoran compounds. All the
synthesized derivatives were identified by conventional methods (IR, 1H-NMR),
elemental analysis and UV-visible spectroscopy in organic solvent and 95 %
acetic acid. All the fluoran compounds change their colour in acidic media.
Keywords: synthesis, bisfluoran compounds, colour change in acidic media.
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J.Serb.Chem.Soc.
68(8–9)615–628(2003) |
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Energy storage in the photosynthetic
electron-transport chain. An analogy with Michaelis-Menten kinetics
DEJAN MARKOVIC
Faculty of Technology,
16000 Leskovac, Serbia and Montenegro (E-mail: dzmarkovic@ptt.yu)
(Received 28 August
2002)
Simultaneous measurements of fluorescence and thermal emission have been
performed by applying combined fluorescence and photoacoustic techniques on
isolated thylakoids pretreated by prolonged illumination with saturating light.
The traces were used to create Lineweaver-Burk type plots, proving clearly at least
a formal analogy between the kinetics of the mechanisms governing fluorescence
and thermal emission from isolated thylakoids and Michaelis-Menten kinetics of
enzymatic reactions. Two characteristic parAMeters were calculated from them
(energy storage and half-saturation light intensity) in order to obtain a
basic, initial response of the photosynthetic apparatus functioning under
photoinhibition stress.
Keywods: photosynthetic electron-transport, reaction centers, energy
storage, fluorescence, thermal emission.
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J.Serb.Chem.Soc.
68(8–9)629–639(2003) |
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Bentonite, stabilizer for suspension
polymerisation
S. KOSEVA, S. BREZOVSKA, V. BOŠEVSKA and D.
BUREVSKI
University “Sv. Kiril i
Metodij”, Faculty of Technology and Metallurgy, Rudjer Boskovic bb, 1000
Skopje, R. of Macedonia
(Received 11 October
2002, revised 7 February 2003)
In suspension polymerizations, stabilizers play a crucial role in the particle
formation. An effective stabilizer must be able to maintain complete coverage
of the surface by both physical and/or anchoring adsorption. In this work the
possibility of using original bentonite and bentonite with a high percentage of
montmorillonite, their acid-activated and monocationic forms as mixed
stabilizer has been investigated. Styrene was used as the monomer. Beads of
polystyrene with spherical or elliptical shape were obtained, depending on form
of the used bentonite. The results are discussed in terms of the acidity of the
mineral surface, AMphiphilic characteristic of the clay and the change of the
contact angle between organic / water / mineral phase.
Keywords: bentonite, stabilization, polymerization, surface pressure, acidic
surface.
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Synthesis and characterization of Co(II), Ni(II), Cu(II) and Zn(II) complexes
with 3-salicylidenehydrazono-2-indolinone
SANDRA S. KONSTANTINOVIC BLAGA C. RADOVANOVIC*, ZIVOJIN CAKIC** and VESNA
VASIC***
Faculty of Technology,
Bulevar Oslobodjenja 124, 16000 Leskovac,
*Department of Chemistry, Faculty of Science, Cirila i Metodija 2, 18000 Nis,
**Institute of Health Protection, 16000 Leskovac and
***INN Vinca, 11000 Belgrade, Serbia and Montenegro
(Received 3 December
2002, revised 16 April 2003)
Abstract: Complexes of Co(II), Ni(II), Cu(II) and Zn(II) with
3-salicylidenehydrazono-2-indolinone were prepared. Their structure was
established to be [MLCl].Cl by using elemental analysis and molar conductivity,
as well as AA, FTIR, UV/VIS and 1H-NMR spectroscopic methods. The
spectral studies indicated a square-planar geometry for the Ni(II) and Cu(II)
complexes and a tetrahedral one for the Co(II) and Zn(II) complexes. The
complexes were tested for antibacterial activity against Staphylococcus
aureus, Enterococcus D, Proteus mirabilis, Escherichia coli, Bacillus
anthracis, Pseudomonas aeruginosa and Candida albicans.
Keywords: isatin, salicylaldehyde, transition metal complexes, FTIR, UV/VIS,
1H-NMR, antibacterial activity.
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J.Serb.Chem.Soc.
68 (8–9)649–656(2003) |
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The current efficiency during the cathodic
period of reversing current in copper powder deposition and the overall current
efficiency
M. G. PAVLOVIC N. D. NIKOLIC and K. I. POPOV*
ICTM - Department of
Electrochemistry, Njegoseva 12, 11000 Belgrade and
*Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4,
11000 Belgrade,
Serbia and Montenegro (E-mail: duki@elab.tmf.bg.ac.yu)
(Received 14 February
2003)
The current efficiency during the cathodic
period of reversing current in copper powder deposition was determined by
measuring the quantity of hydrogen evolved. The diagrAMs from which the
instantaneous and average current efficiencies for copper deposition can be
extracted for any deposition time up to 30 min are given. A procedure for the
calculation of the overall current efficiency is proposed.
Keywords: reversing current (RC), copper powder deposition, current
efficiency in RC copper powder deposition.
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J.Serb.Chem.Soc.
68(8–9)657–663(2003) |
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Kinetic and structural aspects of tantalum
hydride formation
B. R. SIMONOVIC, S. V. MENTUS* and R. DIMITRIJEVIC**
Holding Institute of
General and Physical Chemistry, Studentski trg 12, 11000 Belgrade,
*Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12,
11000 Belgrade and
**Faculty of Mining and Geology, University of Belgrade, Djusina 7, 11000
Belgrade, Serbia and Montenegro
(Received 25 March 2003)
Tantalum hydrides of various composition were synthesized by equilibrating
tantalum with hydrogen at six different temperatures from 573 to 823 K, under a
constant hydrogen pressure of 1 bar. Both the exact Ta/H mole ratios and the
kinetic parAMeters of hydriding were determined on the basis of the dependence
of the H/Ta mole ratio on time. The influence of stoichiometry on the
appearance of X-ray powder diffractogrAMs at room temperature was studied. As a
consequence of hydriding, for ratios H/Ta > 0.2, the original bcc Ta-lattice
undergoes distortion, manifesting itself as both a shift and a splitting of the
X-ray patterns in the X-ray diffractogrAMs. For sAMples with H/Ta < 0.2, the
appearance of some superstructure reflections at low Bragg angles was noted,
which suggests a long range ordering of hydrogen with orthorhombic symmetry.
Keywords: tantalum, hydriding isotherm, hydriding capacity, X-ray
diffractometry.
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J.Serb.Chem.Soc.
68(8–9)665–675(2003) |
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Calculation of activities in some gallium-based
systems with a miscibility gap
DRAGAN MANASIJEVIC, DRAGANA ZIVKOVIC, IWAO KATAYAMA* and ZIVAN ZIVKOVIC
Technical Faculty,
University of Belgrade, VJ12, 19210 Bor, Serbia and Montenegro and
*Osaka Univeristy, Graduate School of Engineering, Department of Materials
Science and Processing, 2-1 YAMadaoka, Suita Osaka, 565-0871, Japan
(Received 5 February,
revised 2 April 2003)
The calculations of thermodynAMic properties in
some gallium-based systems with a miscibility gap – Ga–Tl, Ga–Hg and Ga–Pb are
presented in this paper. The determination of the gallium activities in the
mentioned liquid alloys was based on their known phase diagrAMs using the
Zhang-Chou method for calculating activities from phase diagrAMs involving two
liquid or solid coexisting phases. The activities of gallium in Ga–Tl, Ga–Hg
and Ga–Pb system were calculated in the 973–1273 K, 573–873 K and 1000–1100 K,
temperature ranges, respectively. The activities of the other component in all
the investigated systems were obtained by the Gibbs-Duhem equation. The results
of the calculations are compared with literature data.
Keywords: thermodynAMic calculation, Ga–Tl, Ga–Hg, Ga–Pb systems, phase
diagrAMs, miscibility gap.
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J.Serb.Chem.Soc.
68(8–9)677–684(2003) |
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Sol-gel preparation and electrical behaviour of
Ln: YAG (Ln = Ce, Nd, Ho,
Er)
EDITA GARSKAITE, DARIUS JASAITIS and AIVARAS KAREIVA
Department of General
and Inorganic Chemistry, Vilnius University, Naugarduko 24, LT-2006 Vilnius,
Lithuania (E-mail:
aivaras.kareiva@chf.vu.lt)
(Received 8 January, revised 18 March 2003)
Abstract: A sol-gel method has been developed to prepare pure yttrium aluminum
garnet, Y3Al5O12 (YAG), and rare-earth
substituted (Ce-Y3Al5O12, Nd-Y3Al5O12,
Ho-Y3Al5O12, and Er-Y3Al5O12)
sAMples. The XRD patterns of the polycrystalline powders sintered at 1000ºC
showed the formation of monophasic garnet materials. The micro-structural
features in the polycristalline sAMples were studied by scanning electron
microscopy. A homogeneous distribution of rare-earth dopants in the YAG lattice
was achieved in all of the cases. Electrical conductivity measurements were
also performed on the compacts of sol-gel derived Ln-YAG sAMples. In contrast
to the expected dielectric behaviour, the conducting properties of the exAMined
specimens indicate metallic behaviour with the resistivity increasing gradually
with increasing temperature.
Keywords: sol-gel synthesis, garnet crystals, rare-earth doping, electrical
properties.
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Spectrophotometric determination of ajmaline and
brucine by Folin Ciocalteu’s reagent
DHRUV K. SINGH, BHAVANA SRIVASTAVA and ARCHANA SAHU
Analytical Research Laboratory, Department of Chemistry, Harcourt Butler
Technological Institute, Kanpur – 208 002, India
(Received 8 November
2002)
Abstract: A rapid and simple spectrophotometric
procedure is described for the determination of ajmaline and brucine. The
method is based on the development of blue coloured product due to reduction of
tungstate and/or molybdate in Folin Ciocalteu’s reagent (FCR) by ajmaline and
brucine in alkaline medium. The colour is stable for more than 48 h. The
chromogenic reaction has lmax at 540 nm with molar absorptivity 1.64×104
and 2.37×103 l mol-1 cm-1 in the Beer’s law
range 1–8 mg ml-1 and 10–100 mg ml-1 for ajmaline and brucine, respectively.
Keywords: spectrophotometry, ajmaline, brucine, chemical kinetics, Folin
Ciocalteu’s reagent.
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Determination of uric acid in human serum by an
enzymatic method using N-methyl-N-(4-AMinophenyl)-3-methoxyaniline reagent
MILENA JELIKIC-STANKOV, PREDRAG DJURDJEVIC* and DEJAN STANKOV**
Faculty of Pharmacy,
Department of Analytical Chemistry, Vojvode Stepe 450, P. O. Box. 146, 11224
Belgrade,
*Faculty of Science, P. O. Box 60, 34000 Kragujevac and
**Hospital “Dr Dragi{a Mi{ovi}”, Biochemistry Department, 11000 Belgrade,
Serbia and Montenegro
(Received 8 March 2003)
Abstract: In this work a new enzymatic method for the determination of uric
acid in human serum has been developed. The method is based on the oxidative
coupling reaction between the N-methyl-N-(4-AMinophenyl)-3-methoxyaniline
(NCP) reagent and the hydrogen – donor reagent, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3-methylaniline
(TOOS), in the system involving three enzymes: uricase, peroxidase and
ascorbate oxidase. Using this method uric acid could be determined in
concentrations up to 1.428 mmol/L, with a relative standard deviation of up to
1.8 %. The effect of the medium pH and the NCP concentration on the linearity
of the chromogen absorbance versus the uric acid concentration curve was
investigated. The influence of the uricase activity on the maximum rate of uric
acid oxidation was also exAMined. The use of the NCP reagent demonstrated a
more precise and more sensitive determination of the uric acid compared to the
determination with 4-AMinoantipyrine (4-AA) as the coupling regent. The
sensitivity of the method determined from the calibration curve was 0.71
absorbance units per mmol/L of uric acid; the limit of detection was LOD =
0.0035 mmol/L and the limit of quantification was LOQ = 0.015 mmol/L of uric
acid.
Keywords: uric acid, human serum, enzymatic determination, NCP reagent.
Copyright &AMp; copy; SHD
2003.
October 21, 2003.
For more information contact: SHD@tmf.bg.ac.yu