Chemistry Journal of Moldova

Analytical chemistry

THE MIXTURES OF 2.4-DINITROPHENYLHIDRAZONES OF INFERIOR CARBONYL COMPOUNDS AND THEIR HPLC SEPARATION WITH GRADIENT BINARY MIXTURES PHASES

Author(s):

Gheorghe Zgherea


Field: Analytical chemistry
Type: Research paper
Issue: 2008 Volume 3, no.1
Pages: 52-55
Keywords: acetic aldehyde, diacetyl, 2.4-dinitrophenylhidrazone, reverse phase, low polarity, gradient of mobile phase.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2008.03(1).02

Graphical Abstract:
Mixtures of small quantities of carbonyl compounds are presents in foods, concerning sensorial qualities. The inferior carbonyl compounds (C2-C4, boiling point <100°C) – mono and dicarbonyl – can be identified and measured their concentrations, after a separation by distillation on the water bath. They are transferred in a strongly acid solution of 2.4-dinitrophenylhidrazine (2.4-DNPH), generating a mixture of insoluble 2.4-dinitrophenylhidrazones (2.4-DNPH-ones). The 2.4-DNPH-ones are organic compounds with weak polarity, solids, crystallized, yellows and water insoluble, soluble in organic solvents. The mixture of 2.4dinitrophenylhidrazones may be separated by liquid chromatography, using the reverse phase mechanism [1-3]. This paper contains experimental and theoretical considerations to the means of separation through liquid chromatography of two synthetically and a natural mixtures that contain 2.4-DNPH-ones provided by inferior carbonyl compounds; to obtain conclude results, in the synthetically mixtures was introduce and 2.4-DNPH-ones provided by carbonyl compounds having three (acetone and propanal) and four (isobutyl aldehyde) atoms of carbon.

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CONSIDERATIONS ON LIQUID-CHROMATOGRAPHIC SEPARATION FOR AN EQUIMOLAR MIXTURE OF 2,4-DINITROPHENYLHYDRAZONES OF ACETALDEHYDE AND DIACETYL

Author(s):

Gheorghe Zgherea


Field: Analytical chemistry
Type: Research paper
Issue: 2008 Volume 3, no.1
Pages: 48-51
Keywords: acetaldehyde, diacetyl, reverses phase, polarity, percent of water, inversion of position.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2008.03(1).03

Graphical Abstract:
An equimolar mixture of 2.4-dinitrophenylhidrazones (2.4DNPH-ones) providing by acetaldehyde and diacetyl must be analyzed by liquid-chromatographic separation, using the mechanism of repartition with reverse phase; that full papers is for identification the optimal analytical conditions. As mobile phase are utilized various binary mixtures eluent, containing water and methanol, with 0-45% water. By the experimental studies were identified four domains of behavior and two optimal binary mixtures, with 25% and 45% water, thus this is a study on the behavior of binary mixtures mobile phases. The peaks are characterized by values of retention times and by position. The separation processes were appreciated by difference between the retention times of peaks; if the percent of water increase, the values of retention times is higher. When the percent of water is 45%, the difference between the retention times is maxim, associated with a change of peaks position.

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NITRATE-SELECTIVE ELECTRODES BASED ON THE TRINUCLEAR CHROMIUM(III) PIVALATES

Author(s):

Mihail Revenco, Mariana Martin, Waell A.A. Dayyih


Field: Analytical chemistry
Type: Research paper
Issue: 2008 Volume 3, no.1
Pages: 44-47
Keywords: Trinuclear chromium(III) pivalate, nitrate-sensors.
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Abstract (JPEG)

DOI:
dx.doi.org/10.19261/cjm.2008.03(1).07

Graphical Abstract:
The paper describes the analytical potentialities of the trinuclear chromium(III) complexes as potentiometric ionophores for the construction of electrodes sensitive to the presence of nitrate anion. The electroactive material containing 4,4’-bipyridil was synthesized in situ. The membrane was prepared using dioctylphthalate as a solvent mediator and poly (vinyl chloride) as a polymeric matrix. The electrodes presented a slope of 56 mV/decade, a low limit of detection (3,2.10-6 mol/l), an adequate lifetime (4 months), and suitable selectivity characteristics when compared with other nitrate electrodes. The good parameters of this electrode made possible its application to the determination of nitrate in different types of fertilizers.

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SORPTION OF Ga (III) ON FLEXIBLE OPEN CELL POLYURETHANE FOAM OF POLYETHER TYPE IMPREGNATED WITH TRI-N-BUTHYL PHOSPATE

Author(s):

Lavinia Tofan, Doina Bilba, Carmen Paduraru and Ovidiu Toma


Field: Analytical chemistry
Type: Research paper
Issue: 2007 Volume 2, no.1
Pages: 51-57
Keywords: sorption, polyurethane foam, tri-n-butyl phosphate, gallium.
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DOI:
dx.doi.org/10.19261/cjm.2007.02(1).15

Graphical Abstract: 
The obtained results concerning the Ga (III) ion retention on flexible open cell polyurethane foam of polyether type pretreated with tri-n-butyl phosphate are presented. The influence of solution acidity, phases contact time, Ga (III) concentration and solution temperature have been investigated. The parameters of Ga (III) batch sorption have been optimized. On the basis of Langmuir isotherms, the sorption constants and the thermodynamic parameters, ∆G, ∆Η and ∆S have been calculated.

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