Analytical chemistry

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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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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STUDY CONCERNING THE CORROSIVE ACTIVITY PROPERTIES OF MONATOMIC ALCOHOL-GASOLINE BLENDS

Author(s):

Valerian Cerempei

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.2
Pages: 36-44

Keywords: mixture, butanol, ethanol, corrosion, gasoline, resistance, triethylamine.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(2).09

Graphical Abstract: The paper studies the corrosive activity of the monatomic alcohol (ethanol, butanol) - gasoline mixtures on the materials from which the internal combustion engines are made. The corrosive influence of these blends was determined in dependence of their composition. It was established that the addition of butanol and triethylamine in the ethanol-gasoline mixture essentially reduces the corrosive activity of this mixture.

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DETERMINATION OF COPPER AND ZINC IN MINERAL WATERS BY ATOMIC ABSORPTION SPECTROPHOTOMETRY

Author(s):

Tatiana Mitina, Nadejda Bondarenko, Oxana Bunciuc

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.2
Pages: 45-47

Keywords: mineral waters, microelements, atomic absorption spectrometry.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(2).10

Graphical Abstract: The content of copper and zinc in mineral waters were determined by atomic spectroscopy with preliminary extraction of metals. Validation of the technique was carried out by the method of standard additions and proved the reliability of analytical data.

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PHYSICOCHEMICAL PROPERTIES OF THE GASOLINE AND ALCOHOL BIOFUEL MIXTURES

Author(s):

I. Povar, V. Cerempei and B. Pintilie

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.2
Pages: 48-52

Keywords: alcohol, biofuel, distillation curves, gasoline, Reid saturated vapour pressure, speciﬁc gravity.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(2).11

Graphical Abstract: The influence of added alcohols, ethanol and butanol, on the main biofuel properties, such as the specific gravity, Reid saturated vapour pressure and distillation curves have been investigated. These properties are intimately related to the fuel composition and their prediction relies on the knowledge of its components characteristics. This research proves the possibility of obtaining fuels with different levels of resistance to detonation, using gasoline with different chemical components and various fractions of alcohols.

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PHASE STABILITY OF MONOATOMIC ALCOHOL-GASOLINE MIXTURES FOR DIFFERENT COMPOSITIONS AND HYDRODYNAMIC CONDITIONS

Author(s):

Valerian Cerempei

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.1
Pages: 73-76

Keywords: butanol, ethanol, gasoline, mixtures, phase stability.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(1).08

Graphical Abstract: The article investigates phase stability for the mixtures of monoatomic alcohols (ethanol, butanol) with gasoline in the presence of water. There have been determined the optimal storage conditions of mixtures depending on their composition and mixing conditions. The positive influence of butanol on the phase stability of ethanol-gasoline mixtures was detected.

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VOLTAMMETRIC CHARACTERIZATION OF THE BEHAVIOR OF BIOLOGICALLY ACTIVE COMPOUND ENOXIL IN VARIOUS MEDIA

Author(s):

Gheorghe Nemţoi, Tudor Lupaşcu, Alexandra Ciomaga, Alexandru Cecal

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.1
Pages: 62-68

Keywords: complex biologically active compound Enoxil, cyclic voltammetry, standard redox potential, dosage of pharmaceuticals.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(1).09

Graphical Abstract: This paper presents the results of scientific research related to the electrochemical behavior of the complex preparation Enoxil. It was established that the oxidation-reduction process of Enoxil is quasireversible. The reactivity of Enoxil obtained from alcohol soluble enotannins is more pronounced, compared to that obtained from standard enotannins. The dependence of cathodic current intensity on Enoxil concentration is linear. This can be used to establish Enoxil concentration in solution. Cyclic voltamograms were used to establish reduction and oxidation potential and the formal redox potential on platinum electrode in sodium perchlorate aqueous environment. These features can be used for identification and determination of Enoxil in pharmaceuticals.

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TEMPERATURE INFLUENCE ON PHASE STABILITY OF ETHANOL-GASOLINE MIXTURES

Author(s):

Valerian Cerempei

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.1
Pages: 69-72

Keywords: composition, ethanol, gasoline, mixtures, phase stability, temperature.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(1).10

Graphical Abstract: The article investigates phase stability of ethanol-gasoline mixtures depending on their composition, water concentration in ethanol and ethanol-gasoline mixture and temperature. There have been determined the perfect functioning conditions of spark ignition engines fueled with ethanol-gasoline mixtures.

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TO THE EQUILIBRIUM MODEL CHOICE IN HETEROGENEOUS AQUEOUS SYSTEMS. 1. THEORETICAL BASIS IN THE CASE OF TWO COEXISTING SOLID PHASES

Author(s):

I. Povar, Nina Timbaliuc, Tatiana Cazac, Diana Shepel, Oxana Spinu and Ludmila Chiriac

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.1
Pages: 57-61

Keywords: equilibrium model, heterogeneous system, solubility product, pH value, solid phase.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(1).11

Graphical Abstract: An approach has been developed to determine the equilibrium model in heterogeneous aqueous systems containing a mixture of solid phases from the initial composition of the heterogeneous mixture and the equilibrium values of the pH. This approach allows to significantly reduce the quantity of measured data, properly for solubility measurements. By using the new deduced equations it is possible to determine the solubility products of precipitates on the basis of the known composition of initial mixtures and pH values of saturated solutions avoiding some difficult experimental solubility measurements. The derived relations are useful for solving both direct and indirect equilibrium problems.

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THE INFLUENCE OF THIOSEMICARBAZONE 2,3-DIHYDROXYBENZALDEHYDE ON CATALYTIC CURRENTS IN THE SYSTEM MOLYBDENUM (VI) – POTASSIUM CHLORATE IN ACID SULFATE SOLUTIONS

Author(s):

Ludmila Chiriac, Tatiana Cazac, I. Povar and M. Revenco

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.1
Pages: 52-56

Keywords: voltammetry, catalytic current, molybdenum, thiosemicarbazone 2,3-dihydroxybenzaldehyde, chlorate of potassium.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(1).12

Graphical Abstract: The polarographic catalytic current in acid solutions of Mo(VI), thiosemicarbazone 2,3-dihydroxybenzaldehyde (TSC 2,3-DHBA) and chlorate ions has been investigated. The scheme of reactions, taking place in the solutions and on the electrode, has been proposed. The increase of the catalytic current is explained by the formation of an active intermediate complex [Mo(V)×TSC 2,3-DHBA (ClO^-₃)]. The rate constant of this complex formation K = 2.56 × 10⁶ mol^-1×dm³×s^-1, the activation energy E_a= 15.9 kcal×mol^-1 and the reaction activation entropy ∆S_a^¹ = -23.5 e.u. have been calculated.

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VOLTAMMETRIC BEHAVIOR OF SOME STEELS IN AQUEOUS SOLUTIONS OF HNO3

Author(s):

Gheorghe Nemtoi, Liliana Airinei, Tudor Lupascu and Alexandru Cecal

Field: Analytical chemistry
Type: Research paper
Issue: 2011 Volume 6, no.1
Pages: 45-51

Keywords: corrosion, electrochemical parameters, nitric acid, steels, voltammograms.
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Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2011.06(1).13

Graphical Abstract: The corrosion process of some steels immersed in HNO₃ solutions of different concentrations by means of voltammetric measurements was investigated. For different values of the corrosion potential, or of the contact time: solid steel-aggressive medium, several equations of the type: I = f (E) were proposed, only for linear domains of the voltammograms.

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