Research paper

THE STUDY OF THE BUFFERING CAPACITY OF SEVERAL WATER OBJECTS IN THE REPUBLIC OF MOLDOVA

Author(s):

Angela Lis, Gheorghe Duca, Elena Bunduchi, Viorica Gladchi, Nelli Goreaceva

Field: Ecological chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 30-36

Keywords: buffering capacity, acid-base balance, carbon system, humic system, stability to acidiﬁcation.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).03

Graphical Abstract: The current work represents the estimation of the buffering capacity on the Dniester River waters and its tributaries between November 2008 and October 2009.

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CATALYTIC OXIDATION OF METHYLENE BLUE

Author(s):

T. Lupaşcu, M. Ciobanu, V. Boţan, A. Nistor

Field: Ecological chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 37-40

Keywords: catalytic oxidation, methylene blue, activated carbon.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).04

Graphical Abstract: The intact activated carbon CAN-8, obtained

from nutshells by activation with water vapours, in the presence of oxygen and at relatively low temperatures, possesses catalytic activity, caused by the presence of alkaline functional groups on its surface, as well as by the formation, in these experimental conditions, of the OH radical, which has a high oxidation potential. After 25 cycles of the process of methylene blue oxidation, the data of chromatographic analyses indicate the presence of three organic components in the solution.

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THE POLLUTION SPECTRUM OF OLD PESTICIDES STORAGES IN MOLDOVA

Author(s):

Duca Gh., Bogdevich O., Cadocinicov O., Porubin D.

Field: Ecological chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 41-46

Keywords: soil pollution, POPs, pesticides.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).05

Graphical Abstract: The old pesticide storages in Moldova showed a large quantity of polluted sites. The inventory of POPs polluted sites showed a huge number of extra high polluted sites (more 50,0 mg/kg) which need the first place a remediation or other action to eliminate direct contact with people and animals. The pollution spectrum of POPs is a complex and consists of five groups: DDTs isomers, HCHs isomers, Toxaphene mixture, Chlordane and Heptachlor. The principal groups among these substances are DDTs and HCHs isomers.

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MODIFIED SCREEN-PRINTED CARBON ELECTRODES WITH TYROSINASE FOR DETERMINATION OF PHENOLIC COMPOUNDS IN SMOKED FOOD

Author(s):

V. Dragancea, R. Sturza, M. Boujtita

Field: Food chemistry
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 47-53

Keywords: screen-printed carbon electrode SPCE; biosensor; phenol; tyrosinase; gas chromatography.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).06

Graphical Abstract: A screen-printed carbon electrode modified with tyrosinase (SPCE-Tyr/Paa/Glut) has been developed for the determination of phenol concentration in real samples. The resulting SPCE-Tyr/Paa/Glut was prepared in a one-step procedure, and was then optimized as an amperometric biosensor operating at 0 mV versus Ag/AgCl for phenol determination in flow injection mode. Phenol detection was realized by electrochemical reduction of quinone produced by tyrosinase activity. The possibility of using the developed biosensor to determine phenol concentrations in various smoked products (bacon, ham, chicken and salmon) was also evaluated. Gas chromatography (GC) method was used for result validation obtained in flow injection mode using amperometric biosensor. The result showed good correlation with those obtained by flowinjection analysis (FIA).

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STEROIDAL GLYCOSIDES FROM VERONICA CHAMAEDRYS L. PLANTS. THE STRUCTURES OF CHAMAEDROSIDES A, B, C AND E

Author(s):

Alexandra Marchenko, Pavel Kintia, Bożena Wyrzykiewicz

Field: Natural product chemistry and synthesis
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 54-58

Keywords: steroidal glycoside, NMR analysis, Veronica chamaedrys L.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).07

Graphical Abstract: The paper reports on the structural elucidation of the four steroidal glycosides, where two are new, isolated from Veronica chamaedrys L. plants for the first time on the basis of extensive spectral analysis, including 2D NMR spectral data and chemical evidences.

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OBSERVATIONS ON THE ANTIOXIDANT ACTIVITY OF NOVEL DIHYDROXYFUMARIC ACID DERIVATIVES

Author(s):

N. Secara, Gh. Duca, L. Vlad, F. Macaev

Field: Natural product chemistry and synthesis
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 59-67

Keywords: dihydroxyfumaric acid derivatives, DPPH test, antioxidant activity.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).08

Graphical Abstract: The paper describes the syntheses of new derivatives of dihydroxyfumaric acid and investigations of their antioxidant activities using the DPPH method.

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COMPARATIVE KINETICS STUDY OF THE THERMAL AND THERMO-OXIDATIVE DEGRADATION OF A POLYSTYRENE-CLAY NANOCOMPOZITE BY TGA AND DSC

Author(s):

Ion Dranca, Nicon Ungur,Tudor Lupascu, Oleg Petuhov

Field: Physical chemistry and chemical physics
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 68-72

Keywords: degradation; ﬁre resistance; nanocomposites; thermogravimetric analysis (TGA); differential scanning calorimetry (DSC).
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).09

Graphical Abstract: The methods of thermogravimetry (TGA) and differential scanning calorimetry (DSC) have been used to study the thermal and thermo-oxidative degradation of polystyrene (PS) and a PS-clay nanocomposite. An advanced isoconversional method has been applied for kinertic analysis. Introduction of the clay phase increasers the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials.

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METALLIC COMPOUNDS IN THE PHASE OF THE RETICULATED IONIC POLYMERS

Author(s):

Vasilii Gutsanu, Constantin Turta, George Filoti

Field: Physical chemistry and chemical physics
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 73-82

Keywords: ion exchangers, Mossbauer spectra, iron, superparamagnetic, complexes, polymer phase.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).10

Graphical Abstract: Using the Mossbauer spectroscopy and other physical methods it was demonstrated the presence of different

iron compounds like β-FeOOH, α-Fe₂O₃, and jarosite mineral type compounds: (R₄N,H₃O)[Fe₃(OH)₆(SO₄)₂] or coordination modes: {RCOO-Fe(L4)-OOCR}1+, {R-CO₂=Fe(X₂)=O₂C-R}n, {R-COO-Fe(X₄)-OOC-R}n, and {(-NCH₂CH₂N-)= Fe(X₂) =(-NCH₂CH₂N-)}, where X= H₂O, OH^-, SO₄^2-., n= from 3- to 1+ in the ion-exchange resins (KU-2, AN-31, AV-17, Varian – AD, EDE-10P) after the contact with sulphate of iron(III) solutions at different conditions: type of solvent, temperature, air atmosphere. In special conditions the ultrafine superparamagnetic particles of Fe₂O₃ have been obtained.

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STOPPED-FLOW SPECTROPHOTOMETRIC STUDIES OF THE KINETICS OF INTERACTION OF DIHYDROXYFUMARIC ACID WITH THE DPPH FREE RADICAL

Author(s):

Secara Natalia

Field: Physical chemistry and chemical physics
Type: Research paper
Issue: 2010 Volume 5, no.2
Pages: 83-87

Keywords: DPPH; antioxidant activity; stoichiometry; stopped-ﬂow; kinetics; dihydroxyfumaric acid.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(2).11

Graphical Abstract: The reaction of dihydroxyfumaric acid with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was studied using the stopped-flow method, in order to describe the reaction kinetics. Dihydroxyfumaric acid reacts very rapidly with DPPH, the reaction being completed in several minutes. This 2-stoichiometric reaction proceeds in two stages, with reaction orders of 1 and 0.76 with respect to DPPH, and 0.5 and 0.3 with respect to DHF, respectively. The rate constant of the two stages of the reaction were found to be 39.1 (L/mol•s) and 0.0012 (s^-1) at 20º C and pH 4.0.

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THIOCYANATE ION-SELECTIVE PVC MEMBRANE ELECTRODE

Author(s):

Mihail Revenco, Mariana Martin, Waell Abu Dayyih

Field: Analytical chemistry
Type: Research paper
Issue: 2010 Volume 5, no.1
Pages: 73-77

Keywords: thiocyanate, potentiometric sensor, titration.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2010.05(1).05

Graphical Abstract: A potentiometric selective sensor based on trinuclear

chromium(III) complex as a novel ionophore for the thiocyanateselective electrode is reported. The sensor displays a near Nernstian slope of 57 ± 2 mV per decade, over a wide pH range 3 - 11. The working concentration range of the electrode is 1.10^-5 – 1.10^-1 mol/l with a detection limit of 5.10^-6 mol/l. The sensor has a response time of 20 s and can be used for at least 6 months without any considerable fluctuation of the potential. The selectivity coefficients determined at using the fixed interference method indicate a good discriminating ability towards other anions. The prepared sensor was applied as an indicator electrode in the titration of thiocyanate with Ag⁺.

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