Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry

10-21

Authors: Gheorghe Duca, Elena Bunduchi, Viorica Gladchi, Lidia Romanciuc, Nelli Goreaceva

The current paper contains a synthesis of the processes of chemical auto-purifi cation that take place in natural waters; examples of mechanisms of such processes occurring with participation of dissolved organic matter, oxidants of the biogeochemical cycle of oxygen and of transition metals including copper and iron are presented. The kinetic indicators of natural water quality are presented as well.

31-43

Authors: Ion Dranca

Differential scanning calorimetry has been used to study the α-relaxation (glass transition) in virgin polystyrene (PS), PS-clay nanocomposite, amorphous indomethacin (IM), maltitol (Mt) and glucose (Gl). Variation of the effective activation energy (E) throughout the glass transition has been determined by applying an advanced isoconversional method to DSC data on the glass transition. The relaxations have been characterized by determining the effective activation energies (E) and evaluating the sizes of cooperatively rearranging regions at the glass transition (Vg). The values of Vg have been determined from the heat capacity data. The α-relaxation demonstrates markedly larger values of E (~340 vs ~270 kJ mol-1) for the PS-clay system than for virgin PS. For IM in the glass transition region, the effective activation energy of relaxation decreases with increasing temperature from 320 to 160 kJ mol-1. In the Tg region E decreases (from~250 to ~150 kJ mol-1 in maltitol and from~220 to ~170 kJ mol-1 in glucose) with increasing T as typically found for the α-relaxation. It has been found that in the sub-Tg region E decreases with decreasing T reaching the values ~60 (glucose) and ~70 (maltitol) kJ -1 that are comparable to the literature values of the activation energies for the β-relaxation. Heat capacity measurements have allowed for the evaluation of the cooperatively rearranging region in terms of the linear size The PS-clay system has also been found to have a signifi cantly larger value of Vg, 36.7 nm3 as compared to 20.9 nm3 for PS. Heat capacity measurements of IM have allowed for the evaluation of the cooperatively rearranging region (CRR) in term of linear size (3.4 nm) and the number of molecules (90). The size of CRR have been determined as 3.1 (maltitol) and 3.3 (glucose) nm.

48-51

Authors: Gheorghe Zgherea

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 identifi cation 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 identifi ed 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.

56-61

Authors: Georgiana Vasile, Stanescu Bogdan, Tudor Claudia, Elena Mihaila

An unwanted consequence of human activity and of uncontrolled industrialization is the environment contamination with a lot of pollutants, among them heavy metal anthropogenic pollution having some most serious consequences. A reliable estimation of pollution level is made by studying heavy metal concentrations in the sediments. In our study the zinc content of the water and river sediments has been investigated, in an area polluted by mining activities, to provide information on the mobility and availability of this element. Sediment and water samples have been collected from signifi cant sites in a former mining area in which with some sterile pits, which represent a major environmental hazard. The zinc mobility and bioavailability in the environment was investigated by the three-step sequential extraction procedure, a protocol proposed by the Standards, Measurements and Testing programme (SM & T–formerly BCR) of the European Union. The BCR sequential extraction scheme has the advantage that there are reference materials available with certifi ed and indicative values for the concentrations of selected elements in the particular extraction steps. The BCR procedure enables fractionalization of metal content into the following fractions: • EASILY MOBILIZABLE FRACTION: This fraction contains the specifi cally bound, surface occluded species (sometimes also CaCO3 bound species and metallo-organic complexes with low bonding forces). • ORGANICALLY BOUND FRACTION • Mn-Fe-and Al-OXIDE BOUND FRACTION • RESIDUAL FRACTION: This fraction mainly contains crystalline-bound trace metals and is most commonly dissolved with high concentrated acids and special digestion procedures. Combination of data from sequential extraction procedures and normalisation approaches provides a good basis to estimate the proportions of the easily and sparingly soluble metal fractions in the samples investigated and to identify the anthropogenic input of metals into the environment.

67-69

Authors: N.K. Kulikov, S.G. Kireev, A.O. Shevchenko, V.M. Mukhin, S.N. Tkachenko, T.G. Lupascu

The authors have investigated the equilibrated adsorption of water vapors on GFG hopcalite, which was obtained using the extrusion shaping method, with bentonite clay as the binding compound. In the frames of the BET model, the values of the monolayer capacity and the size of medium area occupied by the water molecule in the fi lled monolayer have been determined. The distribution of pores according to their sizes has been evaluated. It has been established that the modifi cation of the bentonitic clay allows directed construction of the hopcalite porous structure, i.e. the formation of the mesoporous structure with a narrow distribution of the pores capacities by sizes, which was achieved varying the sizes of binding compound particles.

77-84

Authors: Rodica A. Sturza, Olga I. Deseatnicov, Cristina M. Popovici, Valentin S. Gudumac, Ion Nastas

Iodine defi ciency is the most prevalent micronutrient defi ciency in the world today. Food fortifi cation is an important compliment to food-based approaches, and iodine fortifi cation of foods as one of the strategies for the control of iodine defi ciency. Manufacturing and consumption of sunfl ower oil fortifi ed with iodine as well as derivative products on it basis is a perspective direction for elimination of alimentary dependent iodine defi ciency disorders. The present work examines morphological changes in the thyroid system of rats at the experimental mercatholile-induced hypothyroidism. As well it determines the infl uence of iodinated oil and margarine on the thyroid system of rats. It specifi es the safe value of iodinated oil and margarine for rats. In-vivo study demonstrated the effi cacy of fortifi cation of lipid products with iodine under iodine defi ciency status.

89-93

Authors: Irina Lunga, Pavel Kintia , Stepan Shvets, Carla Bassarello, Sonia Piacente, Cosimo Pizza

Ten steroidal saponins have been isolated form the seeds of Hyoscyamus niger L. for the fi rst time and their structures have been elucidated. Seven saponins belong to spirostane series, two are furostane-type and one is pregnane glycoside. Hyoscyamosides B, C and C2 are new steroidal saponins, which have never been reported before in literature. Complete assignments of the 1H and 13C NMR chemical shifts for all these glycosides were achieved by means of one- and two-dimensional NMR techniques, including 1H–1H COSY, HSQC, HMBC and ROESY spectra.

105-11

Authors: N. N. Gorinchoy, I. Ya. Ogurtsov and Ion Arsene

The vibronic origin of instability of the symmetrical forms (D¥ h, C2h and C2v) of the hydrogen peroxide molecule H2O2 was revealed using ab initio calculations of the electronic structure and the adiabatic potential energy curves. The vibronic constants in this approach were estimated by fi tting of the ab initio calculated adiabatic potential in the vicinity of the high-symmetry nuclear confi gurations to its analytical expression. It was shown that the equilibrium “skewed” anticline shape of the C2 symmetry can be realized in two ways: D¥h ® C2v® C2 or D¥h ® C2h® C2 with the decreasing of the adiabatic potential energy at every step.

118-126

Authors: Maria Gonta, Gheorghe Duca, Diana Porubin

This research paper presents the results of the investigation of antioxidant activities of various inhibitors, which are constituents of winery products: quercitin, rezveratrol, dihydroxyfumaric acid. Also, the antioxidant activity of tartaric and dihydroxyfumaric (DFH4) acids derivatives has been determined: sodium dihydroxyfumarate, dimethylic ester of DFH4 and dimethylic ester of tartaric acid. The enotannin extracts obtained from grape seeds have been evaluated: the non-oxidized enotannin extract Eneox and the oxidized one -Enoxil.