INVESTIGATIONS OF THE SYNERGISM IN THE SOLVENT EXTRACTION OF
LANTANOID (III) METALS
I. Dukov
PREPARATION OF COMPLEXES OF L-ASCORBIC ACID WITH SOME TRANSITIONAL
METALS
A. Lyapova, G. Petrov
PREPARATION OF METAL COMPLEXES OF L-ASCORBIC
ACID WITH Zn (II), Cd (II), Cu (II)
A. Lyapova, G. Petrov
EFFECT OF THE DILUENTS ON THE INTERACTION BETWEEN CHELATING
EXTRACTANTS AND THE QUATERNARY AMMONIUM SALT – ALIQUAT 336
I. Dukov, V. Jordanov, M. Atanassova
YTTRIUM - IRON TARTARIC COMPLEXES AS POTENTIAL PRECURSORS FOR
SPRAY-PYROLYSIS DEPOSITION OF YFeO3 THIN FILMS
N. Petrova1, R. Todorovska2, D. Todorovsky1, V. Novakova1, S. Groudeva –
Zotova3
ALTERNATING COPOLYMERIZATION OF
N-(4-CARBOXYPHENYL) MALEIMIDE WITH STYRENE AND a-METHYLSTYRENE
V. Konsulov, D. Alexieva, A. Lyapova, S. Spassov1
ELECTROCHEMICAL NANOSTRUCTURAL TREATMENT AIMING A PREDETERMINED
ATOMIC DESIGN
T. Tzvetkoff, I. Kanazirski
A SAFE MERCURY DROP ELECTRODE
R. Zlatev1, M. Stoytcheva2
AN EXPRESS TURBIDIMETRIC METHOD FOR DETERMINATION OF Mo(VI)
IN LOW CONCENTRATION IN WASTEWATERS
M. Stoytcheva, R. Zlatev, V. Panayotov
CATALYTIC PHOTOMETRIC DETERMINATION OF CHROMIUM(III) IN THE
PRESENCE OF 4-METHYLPIRIDINE
A. Stoyanova
INVESTIGATION OF THE EXTRACTION EQUILIBRIUM OF ION–ASSOCIATE
COMPLEXES OF Mo (VI) WITH SOME POLYPHENOLS AND IODONITROTETRAZOLIUM CHLORIDE
( INT )
V. Lekova, A. Dimitrov, M. Slavova
EXTRACTION-SPECTROPHOTOMETRIC STUDY OF THE SYSTEM VANADIUM(V)
–
4-(2-PYRIDYLAZO) RESORCINOL (PAR) -TETRAZOL VIOLET (TV) - WATER –
1,2-DICHLOROETHANE
K. Gavazov, Z. Simeonova, A. Alexandrov
CATALYTIC PHOTOMETRIC DETERMINATION OF NANOMOLAR CONCENTRATIONS
OF COBALT
M. Angelova, A. Alexiev
AN ICP-AES METHOD FOR STUDYING OF THE VARIATIONS IN THE CHEMICAL
COMPOSITION OF DOPED Bi-BASED SUPERCONDUCTORS
A. Souleva1, K. Konstantinov2, N. Balchev3
THE MODELLING OF ALKYKPHENOL’S RETENTION IN THIN LAYER
CHROMATOGRAPHY BY QSRR APPROACH
M. Moskovkina1, I. Bangov2, R. Aleksandrov1
DIRECT SPECTROPHOTOMETRIC DETERMINATION OF PURINE NUCLEOSIDETRIPHOSPHATES
PRESENT SIMULTANEOUSLY IN A MIXTURE AS COMPLEXES WITH BISMUTH (III) IN PERCHLORIC
ACID MEDIUM
T. Kolusheva, A. Marinova, R. Borisova
SPECTROPHOTOMETRIC FLOW-INJECTION ANALYSIS OF HYDROGEN PEROXIDE
WITH TITANIUM (IV) AND ITS APPLICATION FOR DETERMINATION OF GLUCOSE AND LACTATE,
USING IMMOBILIZED GLUCOSE OXIDASE AND LACTATE OXIDASE
T. Kolusheva1, A. Marinova1, N. Kolushev2
DETERMINATION OF OXYGEN STOICHIOMETRY IN SUPERCONDUCTING BULK
SAMPLES
L. Vladimirova1, T. Nedeltcheva1, A. Stoyanova-Ivanova2
INDIRECT SPECTROPHOTOMETRIC DETERMINATION OF P2O74 - WITH THE
SYSTEM BISMUTH(III) - BERILLON II
L. Nikolova, R. Borissova
VOLTAMMETRIC STUDY ON SYSTEM BISMUTH(III) AND PYROPHOSPHATE
IONS
T. Nedeltcheva, L. Nikolova, R. Borissova
ELECTROCHEMICAL CHARACTERIZATION AND KINETIC MODELLING OF METAL
HYDRIDE ELECTRODES FOR NICKEL – HYDRIDE BATTERIES
T.Tzvetkoff, I. Kanazirski
CORROSION AND ANODIC OXIDATION OF Ni AND Ni-Cr ALLOY IN NaOH
MELTS
P. Gencheva, T. Tzvetkoff
CORROSION AND ANODIC BEHAVIOUR OF PURE Fe IN MOLTEN NaOH
J. Kolchakov, T. Tzvetkoff
THE SURFACE PROPERTIES OF SANDWICH-TYPE CuO/?Al2O3 ADSORBENT
– CATALYST
S. Kitrys, K. Cicinskas, V. Galeckas
SURFACE AREA INVESTIGATION OF K2CO3 SUPPORTED COPPER CATALYSTS
L. Kuzminas, G. Uloziene
TECHNOLOGIES FOR AMMUNITIONS UTILIZATION
T. Tzvetkof, L. Varadinova
INVESTIGATIONS
OF THE SYNERGISM IN THE SOLVENT EXTRACTION OF LANTANOID (III) METALS
I. Dukov
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: dukov@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
A critical survey of the investigations
concerning the synergistic solvent extraction of lanthanoid(III) metals (Ln)
with mixtures of chelating extractants (thenoyltrijluoroacetone (HTTA) or
1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HP)) and high molecular weight amines
(Am) as ammonium salts (AmHA, A = Cl, NO3, ClO4) or quaternary ammonium salt
(QA, A = Cl or ClO4) in various diluents (cyclohexane, benzene, carbon tetrachloride,
chloroform) has been made. It was found that the systems HTTA - AmHA and HTTA
- QA show different extraction behavior. The lanthanoid metals are extracted
with HTTA -- AmHA mixtures as Ln(TTA)3AmHA species until with HTTA- QA mixtures
mixed anionic complexes Q[Ln(TTA)4] are extracted. The two mechanisms could
be explained with the different polarity of the bond between the cation and
the anion in AmHA and QA. The higher polarity of the bond in QA permits easier
bond breaking and Q[Ln(TTA)4] complexes formation nevertheless that the acidity
of HTTA is rather low. Because of the higher pKa value of HP, the lanthanoid
extraction with both HP-AmHA and HP- QA mixtures leads to the anionic complexes
AmH[LnP4] or Q[LnP4] extracti.on. The great injluence of the ammonium salt
anion on the extraction process in the systems HTTA - QA, HP - QA and HP -
AmHA (the values of the overall equilibrium constant decrease 3-4 orders when
in QA or AmHA Cl- is changed with ClO4-) can be explained with breaking of
the bond between the cation and the anion and with the fact that the bond
in QClO4 (AmHClO4) is stronger than those in QCl (AmHCl). Such a great influence
of the salt anion cannot be coordinated with the suggestion of some authors
that the synergist is not the ammonium salt but the ion-pairs Q+.TTA-, Q+.P-
or AmH+.P- obtained by the interaction of the two extractants. If such a compound
was the synergist, the synergistic extraction process should not be influenced
by the salt anion because then the ion pair presence (irrespective of the
anion of the ammonium salt) should be a necessary condition for the occurring
of synergism. According to the Le Chatelier’s principle the equilibrium
should be shifted to the part of the ion-pair formation as it should be spent
for the mixed anionic complex formation. So, the synergistic process should
not depend on the anion of the salt.
In the system HTTA- AmHA the ammonium salt anion exerts a small influence
on the synergistic process as in the complex Ln(TTA)3AmHA the synergist (the
ammonium salt AmHA) is bonded to the metal through its anion (no breaking
of the bond between the cation and the anion).
Keywords: synergistic extraction, chelating extractants,
higt molecular ammonium salts, lanthanoides.
PREPARATION
OF COMPLEXES OF L-ASCORBIC ACID WITH SOME TRANSITIONAL METALS
A. Lyapova, G. Petrov
University “Ep.K Preslavski” of Shumen,
115, Universitetska str., 9712 Shumen, Bulgaria
E-mail: anlqpova@abv.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
Complexes of bioligand L-ascorbic acid with
Co(II), Ni(II), Fe(III) in aqueous-alcohol medium with the participation of
sodium propionate have been obtained.
The cobaltic complex has also been synthesized by metal exchange from previously
obtained sodium ascorbate and cobaltic dichloride hexahydrate in aqueous medium.
Cobaltic complex of ascorbic ester of phosphorus acid is obtained. The composition
of the complexes is determined on the basis of element analysis for carbon,
hydrogen and metal - (L-H)(H2O)2Cl3Co2, [(L-H)3/2(H2O)2Co]n, L2(H2O)2(OH)2Fe2,
L(H2O)2OHClNi2, L(H2O)2PO3ClCo2, where (L-H) is monoanion and (L)2 is dianion
of L-ascorbic acid. It has been established that in all complexes the metal
ion is in octahedron configuration. Their probable structure is proposed on
the basis of IR and UV-VIS spectrum data.
Keywords: L-ascorbic acid, complexes, ascorbato-phosphate,
cobalt(II), nickel(II), iron(III).
PREPARATION
OF METAL COMPLEXES OF L-ASCORBIC ACID WITH Zn (II), Cd (II), Cu (II)
A. Lyapova, G. Petrov
University “Ep.K Preslavski” of Shumen,
115, Universitetska str., 9712 Shumen, Bulgaria
E-mail: anlqpova@abv.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
Investigations
for synthesis of metal complexes of L-ascorbic acid with biological active
metals – Cu (II) and Zn (II), as well as with Cd (II) which is xenobiotic
have been carried out in two ways. One of them is by metal exchange from previously
obtained sodium ascorbate, the another - by the method proposed by Spanish
authors with the participation of sodium propionate. It is determined by element
analysis for carbon, hydrogen and metal that the complexes obtained by both
methods have identical composition: L2 Zn2, [L(OH)Cd2]n , (L-H)Cl3Cu2 where
(L)2 is dianion of L-ascorbic acid and (L-H) is monoanion. Zinc complex of
the well-known ascorbato- phosphoric acid, is synthesized.
The probable structure of the obtained complexes is proposed on the basis
of IR and UV- spectral data.
Keywords: vitamin C, complexes of L-ascorbic acid, ascorbato-phosphate,
zinc(II), cadmium(II), copper(II).
EFFECT
OF THE DILUENTS ON THE INTERACTION BETWEEN CHELATING EXTRACTANTS AND THE QUATERNARY
AMMONIUM SALT – ALIQUAT 336
I. Dukov, V. Jordanov, M. Atanassova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: dukov@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
The interaction between the chelating extractants
1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HP) or thenoyltrifluoroacetone (HTTA)
and the quaternary ammonium salt – Aliquat 336 in chloride (QCl) and
perchlorate (QClO4) forms in CCl4, CHCl3, C6H6 and C6H12 has been studied.
The values of the equilibrium constant Kexc have been calculated on the basis
of the experimental data. The influence of various factors such as diluent
and the anion of the salt on the interaction of the extractants has been discussed.
Keywords: Aliquat 336, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone,
thenoyltrifluoroacetone, diluents.
YTTRIUM
- IRON TARTARIC COMPLEXES AS POTENTIAL PRECURSORS FOR SPRAY-PYROLYSIS DEPOSITION
OF YFeO3 THIN FILMS
N. Petrova1, R. Todorovska2, D. Todorovsky1, V. Novakova1, S. Groudeva –
Zotova3
1University of Sofia, 1, J. Bourchier Blvd., Sofia Bulgaria,
2Institute of Electronics, BAS, Sofia 1784, Bulgaria
3Leibnitz Institute of Solid State and Materials Research, 01171 Dresden,
Germany
E-mail: Todorovsky@inorg.chem.uni-sofia.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
Ethylene glycol solution of the Y-Fe(III)
– tartaric complexes is used as a starting material for spray-pyrolysis
deposition of the YFeO3 thin films. The solution is obtained at conditions
very close to the conditions in the so-called polymerized complex method.
O2 is used as a carrier gas and the substrate (optical grade silica glass)
is heated at 380oC. The films obtained are post-deposition annealed at 750-850oC.
Layers (200 - 1000 nm) with a very good uniformity (proved by SEM and AFM)
but with some phase nonhomogenity are produced.
Keywords: spray pyrolysis, tartaric complexes, thin films,
thermal decomposition, yttrium ferrite.
ALTERNATING
COPOLYMERIZATION OF
N-(4-CARBOXYPHENYL) MALEIMIDE WITH STYRENE AND a-METHYLSTYRENE
V. Konsulov, D. Alexieva, A. Lyapova, S. Spassov1
University of Shumen “K. Preslavski”
1 Institut of Organic Chemistry, BAS, Sofia
|
Received 30 September 2003
Accepted 15 October 2003
|
N-(4-carboxyphenyl) maleimide (CPMI) is synthesised
from maleic anhydride and p-aminobenzoic acid. By free radical polymerisation
in dioxane at 70°C was obtained poly-N-(4-carboxyphenyl) maleimide with
limiting viscosity [?]=0.48 dl/g. It was studied the copolymerization of CPMI
with styrene (St) and a-methylstyrene (MSt) in dioxane at 70°C at an initial
stage and up to high conversions. Two effects of complex forming have influence:
by H-bonds and donor-acceptor interaction, which is the reason of trend to
alternation.
Keywords: maleimide copolymers, alternating copolymerization,
N-substituted maleimides, N-(4-carboxyphenyl) maleimide, styrene, a-methylstyrene.
ELECTROCHEMICAL
NANOSTRUCTURAL TREATMENT AIMING A PREDETERMINED ATOMIC DESIGN
T. Tzvetkoff, I. Kanazirski
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tzvetkoff@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
The electrochemical nanostructural treatment
acquires ever growing application in the technology. The aim of this treatment
is to create a predetermined order on a molecular or an atomic level. The
electrochemical treatment of stainless steel surfaces is widely practiced
aiming to improve the surface state. The present paper reports an investigation
on the mechanism of trans-passive dissolution of Fe alloy containing 12-14%
Cr in concentrated phosphoric acid and mixtures of phosphoric and acetic acids
with the application of linear voltammetry and electrochemical impedance spectroscopy.
Keywords: nanotechnology, electrochemical treatment, atomic
design.
A
SAFE MERCURY DROP ELECTRODE
R. Zlatev1, M. Stoytcheva2
1ZENIT Laboratory, Darvenitza, bl. 17-D-93, 1756 Sofia,
2Department of Chemistry, University of Mining and Geology, 1700 Sofia,
Bulgaria
E-mail: roumen_zlatev@abv.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
The toxicity of mercury used as electrode
material in stripping voltammetry strongly limits its larger application in
spite of its obvious advantages. A construction of a mercury electrode, preventing
mercury pollution would solve this problem. Such a construction of a safe
mercury electrode – SMMDE directed to the stripping voltammetry is described
in the present work. The comparison of the results obtained with the proposed
SMMDE and with a conventional type of electrode – hanged mercury drop
electrode - HMDE in terms of sensitivity, resolution and repeatability shows
the completely identity of their analytical characteristics, when recording
voltammograms of Pb2+, Cd2+, and Zn2+ in HCl and of Ni2+ in ammoniac buffer.
They lead to the conclusion that the new electrode SMMDE, solving the toxicity
problem of mercury electrodes could replace the HMDE in any case of applications.
Keywords: mercury electrode, stripping voltammetry.
AN
EXPRESS TURBIDIMETRIC METHOD FOR DETERMINATION OF Mo(VI) IN LOW CONCENTRATION
IN WASTEWATERS
M. Stoytcheva, R. Zlatev, V. Panayotov
University of Mining and Geology “St. Ivan Rilski”,
1700 Sofia, Bulgaria
e-mail: margarita@mgu.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
It is known that Mo(VI) forms, with potassium
ethyl xanthogenate in acid media, a slightly soluble in water compound with
a red-violet color. After the extraction of this compound with organic solvents,
the concentration of Mo(VI) can be spectrophotometrically determined. However,
the extraction prolongs the analysis and introduces the errors in the determinations,
especially for the low concentrations of Mo(VI).
In this work, the possibility of direct turbidimetric determination of Mo(VI)
in low concentration is discussed. It has been experimentally established
that the diffuse density of the suspension of the little soluble compound,
obtained from the interaction between Mo(VI) and potassium ethyl xanthogenate,
measured at 400 nm, is a linear function of the concentration of Mo(VI) up
to 3 ppm. This has been applied for the determination of Mo(VI) in waste waters.
Keywords: Mo(VI), turbidimetric determination, waste waters.
CATALYTIC
PHOTOMETRIC DETERMINATION OF CHROMIUM(III) IN THE PRESENCE OF 4-METHYLPIRIDINE
A. Stoyanova
Higher Medical Institute - Pleven
St. Kl. Ohridski street 1, 5800 Pleven;
E-mail: astoy@abv.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
In this work a catalytic photometric method
for determination of chromium(III) is proposed. The method is based on the
catalytic effect of chromium(III) on the oxidation of sulfanilic acid by hydrogen
peroxide in the presence of 4-methylpiridine (?-pic) as an activator.
The reaction rate was monitored photometrically by following the formation
of the coloured reaction product as a function of time. The measure of the
reaction rate was the initial straight-line portions of the kinetic curves
(tan?= ?A/??).
On the basis of the investigation results, the optimum reaction conditions
were established.
The proposed method permits chromium(III) determination over the linear range
5 - 100 ng ml-1 with detection limit 3.2 ng ml-1 and RSD (n=6) 5.4%.
Keywords: chromium(III), catalytic method, sulfanilic acid,
4-methylpiridine.
INVESTIGATION
OF THE EXTRACTION EQUILIBRIUM OF ION–ASSOCIATE COMPLEXES OF Mo (VI)
WITH SOME POLYPHENOLS AND IODONITROTETRAZOLIUM CHLORIDE ( INT )
V. Lekova, A. Dimitrov, M. Slavova
Plovdiv University P. Hilendarski
24 Tsar Assen Str., 4000 Plovdiv, Bulgaria
E-mail: vanlek@ulcc.pu.acad.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
It is known that in aqueous solution, Mo(VI)
forms coloured complex acids with some polyphenols, wich interact with organic
bases and form ion – association complexes. These associates are easily
extracted in organic solvents. On this basis we studied the reaction between
Mo(VI) and polyphenols (4–nitrocatechol /4–NC/ and 2,3–dihydroxynaphtalene
/DHN/), and the iodonitrotetrazolium salt INT in aqueous medium. Also, we
examined the extraction of the obtained ion associates in organic phase. The
extraction process has been investigated quantitatively. The extraction, distribution
and association constants and the recovery factor have been calculated. The
molar ratios of the components in the studied associates have been determined.
Our investigations show, that the ion – associate of Mo(VI)–NC–INT
allows analysis of higher sensitivity. Based on these studies a method for
Mo determination in products from the ferrous metallurgy was developed. The
results of the analysis are evaluated statistically.
Keywords: molybdenum, tetrazolium salts, extraction –
spectrophotometry, polyphenols.
EXTRACTION-SPECTROPHOTOMETRIC
STUDY OF THE SYSTEM VANADIUM(V) –
4-(2-PYRIDYLAZO) RESORCINOL (PAR) -TETRAZOL VIOLET (TV) - WATER –
1,2-DICHLOROETHANE
K. Gavazov, Z. Simeonova, A. Alexandrov
Plovdiv University “P. Hilendarski”
24 Tsar Assen Str., 4000 Plovdiv, Bulgaria
E-mail: kgavazov@abv.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
The system vanadium(V) - 4-(2-pyridylazo)-resorcinol
(PAR) - tetrazol violet (TV) - water - 1,2-dichloroetane is studied using
an extraction-spectrophotometric method. The optimum conditions for extraction
of vanadium are found: reagent concentration in aqueous phase - CPAR=CTV=2.0x10-4
mol l-1, pH=5.8, extraction time - 2 min. Beer’s law is obeyed in the
concentration interval 0.5 - 25 ?g V(V) / 10 mL. Molar absorptivity calculated
using the Beer’s law is ?555 = 4.0x104 L mol-1 cm-1. Under the optimum
extraction conditions the dominating vanadium species is established to be
V(V):PAR:TV = 1:2:3. The following constants are calculated: distribution
constant (LogKD=1.48), association constant (Log?=16.4), extraction constant
(LogKex=17.9), recovery factor (R=96.8%). The effect of foreign ions on the
extraction of vanadium is studied as well.
Keywords: vanadium, PAR, tetrazol violet, ternary complex,
extraction-spectrophotometry.
CATALYTIC
PHOTOMETRIC DETERMINATION OF NANOMOLAR CONCENTRATIONS OF COBALT
M. Angelova, A. Alexiev
Higher Medical Institute - Pleven
St. Kl. Ohridski street 1, 5800 Pleven;
E-mail: angelovamg@abv.bg
|
Received 30 September 2003
Accepted 15 October 2003
|
The analytical chemistry of traces of cobalt
is a problem of the present day, because cobalt is found in waters, pure metals,
alloys, medicines, soils, living organisms, etc.
A catalytic reaction for the determination of nanomolar concentrations of
Co(II), i.e. oxidation of L-adrenaline-D-hydrogentartrate (AT) with H2O2 is
proposed. At the optimum reaction conditions (8.0x10-3 M AT and 1.5x10-2 M
H2O2 , pH=10.7, to=50o C, ?max=360 nm and fixed time 3 min.) an elaborated
catalytic photometric method achieves low limit of detection of 2.0x10-9 M
Co(II), good reproducibility with R.S.D of 4 - 5 % in the Co(II) concentration
range 8.0x10-9 - 8.0x10-8 M and good selectivity. The regression equation
of the linear calibration plot is A3= 0.170 + 0.005.CCo(II) with a correlation
coefficient of r=0.9900.
The method is applicable for determination of traces of cobalt in samples
of different origin.
Keywords: catalytic photometric determination, cobalt.
AN
ICP-AES METHOD FOR STUDYING OF THE VARIATIONS IN THE CHEMICAL COMPOSITION
OF DOPED Bi-BASED SUPERCONDUCTORS
A. Souleva1, K. Konstantinov2, N. Balchev3
1University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: soulevi@yahoo.com
2 Institute of General & Inorganic Chemistry, BAS, 1040, Sofia
3 Institute of Solid State Physics, BAS, 1784, Sofia
|
Received 30 September 2003
Accepted 15 October 2003
|
An investigation of the element concentration
variations in the Bi-containing superconductors during synthesis was carried
out. An ICP- AES method for determination of the main elements such as Bi,
Sr, Ca, Cu and Y and additives such as Pb, Sb, alkaline metals, Cd and Sn
was developed. The results of the analysis for the final compositions compared
to the nominal ones showed a significant loss of Pb as a function of the annealing
time. Drastic losses of the alkaline metal additives - Li, Na, K, Rb and Cs
during the synthesis of the superconductors were found. No decrease of element
concentrations in the Cd-doped system was observed. The analysis confirmed
the presence of Sn in the synthesized samples.
Keywords: ICP-AES; Bi-based superconductorts.
THE
MODELLING OF ALKYKPHENOL’S RETENTION IN THIN LAYER CHROMATOGRAPHY BY
QSRR APPROACH
M. Moskovkina1, I. Bangov2, R. Aleksandrov1
1 Konstantin Preslavski University Shumen,
115 Universitetska Str, 9712 Shumen,
E-mail: marinam@shu-bg.net
2 Molecular Networks GmbH, Computerchemie, Neagelsbachstr. 25, 91052,
Erlangen, Germany
|
Received 30 September 2003
Accepted 15 October 2003
|
The Quantitative Structure Retention Relationship
(QSRR) approach has been applied to model the retention of the 19 alkylphenols
chromatographed on thin layer of cellulose impregnated with formamide. More
than 20 molecular indices employed as descriptors in the QSRR multi-parametric
regression equations have been studied. The charge-related topological index
(CTI) have been investigated as a molecular descriptor for QSRR deriving.
The analysis of the equations derived with different descriptors proves their
ability to describe and evaluate the participants in the chromatographic retention
process.
Keywords: QSRR, Retention Modeling, Thin Layer Chromatography,
alkylphenols.
DIRECT
SPECTROPHOTOMETRIC DETERMINATION OF PURINE NUCLEOSIDETRIPHOSPHATES PRESENT
SIMULTANEOUSLY IN A MIXTURE AS COMPLEXES WITH BISMUTH (III) IN PERCHLORIC
ACID MEDIUM
T. Kolusheva, A. Marinova, R. Borisova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tinka_kolusheva@hotmail.com
|
Received 30 September 2003
Accepted 15 October 2003
|
A method for spectrophotometric determination
of purine nucleosidetriphosphates present simultaneously in a mixture, based
on the complex formation with bismuth (III) in perchloric acid medium (pH~2,
CClO =0.01 mol l-1) is proposed. The absorption maxima of the complexes are
in the UV-region: 248 nm (BiITP), 258 nm (BiATP), 258 and 284 nm (BiGTP).
The calibration is carried out with regards to external standards for three
different wavelengths: 248 nm, 258 nm, and 284 nm. The determined molar absorptivities
are included into a system of three equations which is solved using matrices.
For the determination of the precision and the reproducibility of the analysis,
test solutions containing a mixture of the three nucleotides are developed
and analyzed. The values obtained for RSD are below 2.80% for BiITP, below
3.10% for BiATP and below 3.14% for BiGTP.
Keywords: spectrophotometry, purine nucleosidetriphosphates,
perchloric acid medium, bismuth (III).
SPECTROPHOTOMETRIC
FLOW-INJECTION ANALYSIS OF HYDROGEN PEROXIDE WITH TITANIUM (IV) AND ITS APPLICATION
FOR DETERMINATION OF GLUCOSE AND LACTATE, USING IMMOBILIZED GLUCOSE OXIDASE
AND LACTATE OXIDASE
T. Kolusheva1, A. Marinova1, N. Kolushev2
1University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tinka_kolusheva@hotmail.com
2Institute of Animal Breeding, Kostinbrod, Bulgaria |
Received 30 September 2003
Accepted 15 October 2003
|
Rapid determination of H2O2, based on the
spectrophoto-metric measurement of its complex with titanium (IV) in sulphuric
acid medium, is adapted for flow-injection analysis (FIA). The FIA system
is developed in two variants: bichannel – for analysis of H2O2 only,
and – trichannel, which includes enzymic bioreactors with immobilized
oxidase enzymes on zeolites. With the FIA described, a speed of 120 samples/hour
is achieved. The method is applied for analysis of glucose and lactate in
serum and fermentation fluids after their enzymic oxidation by immobilized
glucose oxidase (GOD) and lactate oxidase (LOD). The method was calibrated
against the amperometric method and a good correlation was obtained between
the two methods over a wide range of glucose and lactate values. The linear
dynamic region for measurement of standard solutions of H2O2 is from 0.34
to 102 mg dl-1, for glucose from 2 to 250 mg dl-1 and for lactate from 4 to
280 mg dl-1.
Keywords: hydrogen peroxide, titanium (IV), flow-injection
analysis, immobilized enzymes.
DETERMINATION
OF OXYGEN STOICHIOMETRY IN SUPERCONDUCTING BULK SAMPLES
L. Vladimirova1, T. Nedeltcheva1, A. Stoyanova-Ivanova2
1University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: lkv@uctm.edu
2Institute of Solid State Physics, BAS,
Blvd.Tzarigradsko Chaussee 72, Sofia 1784, Bulgaria
|
Received 30 September 2003
Accepted 15 October 2003
|
The ability for determination of oxygen
stoichiometry in YBCO superconductors, in which up to 30 % of Y3+ are substituted
with Ca2+ions, is studied. It is proved that the spectrophotometric method
(Anal.Chim.Acta, 437, 2001, 259) for the determination of the non-stoichiometric
oxygen in non-substituted YBCO materials can be successfully applied for oxygen
analysis of Y1-xCaxBa2Cu3Oy (x = 0.1, 0.2 and 0.3) superconducting bulk samples.
Keywords: spectrophotometry, oxygen, calcium substituted
YBCO superconductors.
INDIRECT
SPECTROPHOTOMETRIC DETERMINATION OF P2O74 - WITH THE SYSTEM BISMUTH(III) -
BERILLON II
L. Nikolova, R. Borissova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
|
Received 30 September 2003
Accepted 15 October 2003
|
The complex forming processes in the system
Bi(III) –pyrophosphate - Berillon II are studied by a spectrophotometric
method. The experiments are carried out at Bi(III) concentration from 4,0.10-5
mol.l-1 to 9,3.10-5 mol.l-1; pyrophosphate concentration - 4.10-5 mol.l-1,
pH of solution 1,9 ± 0,05.
The formation of a 1:1 complex Bi(III)-Berillon II has been proved by the
method of continuous variation, the mol-ratio method and the Bent - French’s
method. The value of the conditional stability constant has been determined.
The absorbance depends linearly on the concentration of pyrophosphate in the
region 4.10-5 to 1,2.10-4 mol.l-1.
Keywords: spectrophotometric determination, bismuth(III),
pyrophosphate, Berillon II.
VOLTAMMETRIC
STUDY ON SYSTEM BISMUTH(III) AND PYROPHOSPHATE IONS
T. Nedeltcheva, L. Nikolova, R. Borissova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: nedel@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
The complex forming processes in the Bi(III)
- pyrophosphate system are studied with differential pulse polarography (DPP).
The experiments are carried out at Bi(III) concentration - 5. 10-6 mol.l-1,
pyrophosphate concentration - from 1.6 to 16 10-3 mol.l-1; temperature - 20
± 0.50C; pH of the solution - 0.9 ± 0.5; ion strength, µ=1.0,
maintained by KNO3. Applying the equation of De Ford and Hume and this of
Leden to DPP data, the existence of one complex is proved. The ligand number
and the conditional stability constants are 1 and 1.103, respectively.
Keywords: Bismuth, pyrophosphate, complex, differential pulse polarography.
ELECTROCHEMICAL
CHARACTERIZATION AND KINETIC MODELLING OF METAL HYDRIDE ELECTRODES FOR NICKEL
– HYDRIDE BATTERIES
T.Tzvetkoff, I. Kanazirski
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tzvetkoff@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
The batteries with porous metalhydride electrodes
make lately their way into practice. These batteries have high specific energy
and their application in electromobiles is perspective because of their low
weight when compared to lead acid batteries. The unstable oxidation-corrosion
behavior of metalhydride electrodes during prolonged cycling is one of the
basic barriers, which prevents their wide application. In this work the voltammetric
and impedance investigation of AB5 alloy are presented. The interpretation
of the experimental data is based on a kinetic model accepted in the literature.
Keywords: metal hydride electrode, voltammetric investiga-tion,
impedance spectroscopy, nickel-hydride batteries.
CORROSION
AND ANODIC OXIDATION OF Ni AND Ni-Cr ALLOY IN NaOH MELTS
P. Gencheva, T. Tzvetkoff
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tzvetkoff@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
The corrosion and anodic oxidation of Ni
and Ni-10%Cr in molten hydroxide is studied by linear sweep voltammetry, potentiostatic
polarisation and X-ray diffraction analysis of the scale. Slow scan rate polarisation
curves allow the definition of four potential regions – active region,
prepassive region, passive region and transpassive region in which oxidative
decomposition of the melt also occurs. In the active region, a two step reaction
of dissolution of Ni is evidenced. The dominant process in the prepassive
region is probably formation of nickel hydroxide and its transformation to
nickel oxide. In the passive region the main phase in the oxide film was found
to be NiO by X-ray diffraction analysis. It is hypothesised that a cation
vacancy transport is the limiting factor of film formation. The transpassive
corrosion is probably related to enhanced dissolution of the metal substrate
to high-valent nickel species in the melt. The main process in that region
is thought to be further oxidation of NiO phase to NiO2 onto which decomposition
of the melt with liberation of oxygen takes place.
Keywords: nickel, nickel-chromium alloy, molten hydroxide,
passive film, voltammetry.
CORROSION
AND ANODIC BEHAVIOUR OF PURE Fe IN MOLTEN NaOH
J. Kolchakov, T. Tzvetkoff
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tzvetkoff@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
Voltammetric measurements were used to evaluate
the corrosion behaviour of pure Fe in molten NaOH at 470°C. The areas
of corrosion, passivity and transpassivity were derived from experimental
voltammetric data and thermodynamic considera-tions. Some indications of the
rate limiting stages in the different regions were also evidenced. Preliminary
data on the surface composition of the passive film is estimated by XPS are
also presented.
Keywords : pure iron, molten NaOH, high temperature corrosion.
THE
SURFACE PROPERTIES OF SANDWICH-TYPE CuO/?Al2O3 ADSORBENT – CATALYST
S. Kitrys, K. Cicinskas, V. Galeckas
Kaunas University of Technology
Radvilenu str. 19, LT – 3028 Kaunas, Lithuania
E-mail: saulius.kitrys@ktu.lt
|
Received 30 September 2003
Accepted 15 October 2003
|
CuO/?Al2O3 adsorbent – catalyst was
prepared by wet impregnation method. The products were characterized by XRD,
DTA, AAS and BET methods. It was established that the amount of CuO phase
formed and its specific surface, pore volume, pore size and active phase distribution
on the support surface depends on the impregnation solution concentration
and on the impregnation time. Specific surface area of the outer (with CuO)
layer of adsorbent-catalyst SBET (outer) = 150,29 m2/g and comparing to inner
(without CuO) layer specific surface area (SBET (inner) = 171,04 m2/g) decreased
by 12,13 %. During the catalyst preparation pores with rp = 3,4 – 3,8
nm were blocked. Adsorbent-catalyst is mezoporic. According to the De Boer
classification, cylindrical pores are prevailing in this adsorbent-catalyst.
The activity of the adsorbent – catalyst was tested for the removal
of methanol vapors. The process was carried out at two stages: methanol vapor
adsorption at ambient temperature and catalytic total oxidation of adsorbate
at 350 – 450oC in air flow.
Keywords: oxide catalysts, copper oxide, methanol oxidation,
catalyst.
SURFACE
AREA INVESTIGATION OF K2CO3 SUPPORTED COPPER CATALYSTS
L. Kuzminas, G. Uloziene
Kaunas University of Technology
Radvilenu str.19, LT-3028 Kaunas, Lithuania
E-mail: linaskuzminas@kis.lt
|
Received 30 September 2003
Accepted 15 October 2003
|
The catalysts on the basis of pumice were
prepared using high temperature technology and a variety of additional components
(CaO, MgO, CuO, K2CO3). CuO is an active component concentrated on the surface
of catalyst. These catalysts were manufactured for methanol adsorption - catalytic
oxidation processes. The analysis of dependencies of pores radii distribution
and surface area on the amount of additional components was carried out.
It was found that SBET depends on the composition of catalysts. For the catalysts
without K2CO3 the supplement SBET is 1,21 m2/g. The addition of K2CO3 reduces
SBET. Surface structure for the samples of catalysts was evaluated by adsorption
– desorption isotherms. Using Kelvin and De Boer methodology the hysteresis
loops show that catalysts have spherical form mezopores with radii 1,5 –
7,5 nm.The macroporic part of the surface area is 2.4 – 5.0 %.
Surface area of the same composition catalysts also depends on the heating
environment.The use of the inert environment (N2) during manufacturing of
catalysts has allowed to increase specific surface area and porosity of catalysts.
These samples, differentiated by their composition were picked up separately
and analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy
(XPS).
Keywords: copper catalysts, surface area, catalysts composition,
BET.
TECHNOLOGIES
FOR AMMUNITIONS UTILIZATION
T. Tzvetkof, L. Varadinova
University of Chemical Technology and Metallurgy,
8 Kl. Ohridski, 1756 Sofia, Bulgaria
E-mail: tzvetkoff@uctm.edu
|
Received 30 September 2003
Accepted 15 October 2003
|
A system was developed for the utilization
of valuable components of unserviceable ammunitions, as a constituent part
of the National Program of the Bulgarian army for destruction and utilization
of surplus ammunitions within the framework of the pre-acceptance procedures
for NATO membership.
The technologies for the utilization of unserviceable explosives and powder
are oriented to civil applications - industrial explosions in the ore output
and housing construction, nitrocellulose varnishing compositions, fuel materials.
After a suitable separation are utilized the polymeric materials (thermoreactive
and thermoplastic). Metals and alloys are treated in accordance with their
composition, type and the complexity of the article subjected to utilization.
A technology was developed for the secondary processing of aluminum and aluminum
alloys being separated from special articles with complicated design.
A system for the assessment of environmental risk in the utilization process
of unserviceable ammunitions of the Bulgarian army was developed.
Keywords: utilization, ammunitions, waste free technologies,
environmental risk.
