Volume 61, Issue 6

This review summarizes all significant data regarding peroxynitrite chemistry, the ways of its synthetic preparation as well as the degradative action of this species on biomolecules, in particular glycosaminoglycans, among which the hyaluronan degradation by peroxynitrite has recently been the subject of greater interest than ever before. The complex chemical behavior of a peroxynitrite molecule is strongly influenced by a few factors; conformational structural forms, active intermediates release, presence of CO2 and trace transition metals, different reaction conditions, as well as the rules of kinetics. Special attention was focused on monitoring of the kinetics of the degradative action of peroxynitrite in or without the presence of residual hydrogen peroxide on high-molar-mass hyaluronan.

Feasibility and limitations of direct coupling of high performance liquid chromatographic (HPLC) separation to microwave induced plasma (MIP)-optical emission spectrometry (OES) for elementspecific detection was tested and compared to inductively coupled plasma (ICP)-optical emission spectrometric detection on the basis of the Cr(III)/Cr(VI) speciation analysis of water samples. Coupling was performed by a hydraulic high pressure nebulizer (HHPN) radiative-heating/watercooling interface which provides about 20 % and 80 % aerosol yield in the case of helium and argon carrier gases, respectively. Desolvation efficiency of aqueous solutions was approximately 80 %. Applying the ion-pair HPLC separation, the organic eluents and reagents in the MIP cause a 50–75 % signal suppression for Cr(VI) and 25–50 % for Cr(III). In a pure aqueous solution the MIP Cr(VI) signal was by 20 % lower than that of Cr(III). These effects were lower using the ICP source, but they cannot be neglected. Easily ionizable matrix elements (Na, Ca) can cause 70 % signal suppression in the MIP, and 20 % in the ICP. Therefore, species dependent calibration is required in both cases. In the case of HPLC detection by MIP-OES, the detection limit was 13 ng for Cr(III), and 18 ng for Cr(VI). Using the ICP-OES detection, the detection limit was 0.2 ng for Cr (III) and 0.4 ng for Cr (VI). The linear dynamic ranges in both cases were two orders of magnitude.

A facile, sensitive and rapid spectrophotometric method for the determination of nitrite is presented. The method involves the reaction of nitrite with 4-aminoazobenzene under acidic conditions in the presence of a bromide ion allowing to complete the diazotization reaction almost instantaneously. The formed diazonium ion is then coupled with acetyl acetone to give bisazo dye in an aqueous alkaline medium having maximum absorption at 500 nm. The molar absorptivity and Sandell’s sensitivity of the method were found to be 4.2 × 104 dm3 mol−1 cm−1 and 1.1 ng cm−2, respectively. The system obeys the Beer’s law within the concentration range of 0.1–9 µg of nitrite in the final sample volume of 10 cm3. Optimum reaction conditions were evaluated and the influence of ionic interference on the determination of nitrite has been studied. The developed method has been applied in the determination of nitrite in water and soil samples, and the results were statistically evaluated.

Arsenic(III) was preconcentrated in a flow-through electrochemical cell on a gold coated porous carbon electrode. On stripping, arsenic was eluted with diluted nitric acid and determined off-line by GF AAS. The deposition and stripping steps were optimized. The limit of detection and limit of quantification were found to be 1.9 µg L−1 and 6.4 µg L−1, respectively. The repeatability and reproducibility were found to be 5.3 % and 9.3 %, respectively. Total arsenic was determined after a microwave assisted chemical reduction of As(V) to As(III) making the procedure suitable for speciation analysis. The method was applied in analysis of water samples.

An energy and technological study of processing SO2-containing metallurgical gases from zinc production to sulfuric acid production using the exergy method of thermodynamic analysis has bean carried out. A real operating installation since 2003 at the KCM-SA, Plovdiv, Bulgaria, has been used as the model scheme. The principal production stages have been analyzed. The absolute and the relative exergy characteristics of the separate stages as well as of the process as a whole have been calculated. The results have been used to evaluate the influence of sulfuric acid production on the environment. The results obtained have been compared with previous studies on similar processes both in zinc and in copper production. The studied installation of sulfuric acid production has good exergoecological indices, defining it as an effective process both in thermotechnical and in ecological aspects.

The incorporation of 9,10-anthraquinone-1,5-disulfonate (AQS2) into the protonated form of poly(o-toluidine) (POT), produced by oxidative polymerization of the cationic form of the monomer or by doping the basic form (POT-EB) by anion-exchange has been studied by FTIR and UV-VIS spectroscopy and mass spectrometry. The presence of sulfur and the absence of chlorine proven by elemental analysis of the polymer product confirmed the substitution of the chloride anion with AQS2 in the matrix. Molecular mechanics (MM+) calculations suggest that the optimal geometric structure (OMG) of AQS2-doped POT is at least three (3.92) times more stable than that of the parent chloride-doped POT (HCl-doped POT). The increase of the absorbance at about 840 nm associated with the increasing concentration of AQS2 revealed the insertion of AQS2 into the POT chain. This observation could be explained by the diffusion of AQS2 in the polymer chain. Kinetic parameters of the oxidative polymerization of the cationic form of o-toluidine (o-T-HClO4) in the presence of different amounts of AQS2 were deduced on the basis of absorbance variations. The results of computer-oriented kinetic analysis indicate that the rate-controlling step of the o-T polymerization is governed by the Ginstling-Bronstein equation representing the three-dimensional diffusion (D4). Activation parameters of the oxidative polymerization of protonated o-T in the presence of varying amount of AQS2 were computed and discussed.

Pulps obtained from ethanol/water cooking of sugarcane bagasse were treated at different times using xylanase enzyme obtained from Thermomyces lanuginosus IOC-4145 or commercially (Cartazyme HS, Sandoz Products Ltd.). The enzyme dosage was 18 IU per g of dry pulp and the time varied from 4 h to 12 h. When xylanase from T. lanuginosus was used, the kappa number and viscosity improved independently of the processing time used (4 h, 8 h, and 12 h). After chemical evaluation, the obtained pulps were classified using Fourier Transformed Infra-Red Spectroscopy and Principal Component Analysis. The results showed that the first three principal components explained more than 90 % of the total variance of the pulp spectra.

Porous calcium phosphate ceramics were prepared by sintering of mixtures of nanocrystalline apatitic calcium phosphate and fibrous natural cotton cellulose after pressing at temperatures of 1150 °C and 1250 °C. Micro-and macropores were present in microstructures of ceramic samples. The microstructures of porous ceramics were similar to those observed in bone tissues and fiber-like randomly oriented texture was observed in ceramics. Polyhydroxybutyrate (PHB) biopolymer layers are distributed homogeneously in the samples after evaporation of the diluent (chloroform) from the PHB vacuum impregnated porous samples. The tetracycline (TTC) release rate decreases with the content of polyhydroxybutyrate in the ceramic samples, which corresponds to the rise in amount of biopolymer displaced in the pores of ceramics. The concentration of TTC in the phosphate buffer saline solution varies almost linearly with time after the first seven hours from the start of the release of the calcium phosphate ceramic samples with 2.4 mass % of polyhydroxybutyrate. The initial burst effect was significantly depressed by the preparation method used.

Metal complexes of some divalent metal ions (Co, Ni, Cu, Zn, Hg, and Pd) with isatin-β-thiosemicarbazone (ITS) as the Schiff base have been investigated potentiometrically and spectrophotometrically. The dissociation constants of the ligand and formation constants of the metal complexes, as well as the corresponding thermodynamic functions (ΔG, ΔH and ΔS) have been determined at different temperatures in ethanol—water solution. The full stability constants were also evaluated spectrophotometrically by the Job method. The experimental results indicate that Cu(II), Zn(II), Pd(II), and Hg(II) form one-to-one molecular complexes (ML) with the studied ligand, whereas Co(II) and Ni(II) form both ML and ML2 species.

Dipeptide l-methionyl-glycine (Met-Gly) hydrochloride was characterized structurally by means of solid-state linear polarized IR (IR-LD) spectroscopy of oriented samples as colloidal suspension in nematic liquid crystal. Quantum chemical ab initio calculations and vibrational analysis support the experimental data. 1H and 13C nuclear magnetic resonance (NMR) data, mass spectrometry (ESI-MS and FAB-MS) techniques, thermogravimetry (TGV), and differential scanning calorimetry (DSC) method were employed as well. The experimental and theoretical data of hydrochloride salt were compared with analogous data of the neutral dipeptide with the aim to explain the role of intermolecular hydrogen bonding on the conformational behavior and spectroscopic properties of the compound studied.

The densities of the (cyclohexane + pentane, or hexane, or heptane, or octane, or nonane) systems were measured at the temperature 298.15 K by means of a vibrating-tube densimeter. Their respective excess molar volumes were calculated and correlated using the fourth-order Redlich—Kister equation, with the maximum likelihood principle being applied in the determination of the adjustable parameters. The values of excess molar volumes were negative for the cyclohexane + pentane system, whereas they were positive for the other systems with the values increasing with the number of carbon atoms in the respective alkane molecules.

Solid-state IR and Raman spectroscopic elucidation of alaninamide acetate is preformed by means of the possibilities of linear-polarized IR and Raman methods. The experimental assignment is compared with theoretical vibrational analysis with the intention to explain the influence of intermolecular interactions in solid phase on the spectroscopic properties of the compound studied. The 1H and 13C NMR spectra in solution are compared with the corresponding ones of alanine, studying the amidation effect on the chemical shift signals in the alanine moieties.

A series of alkyl- and arylsulfanylpyridylguanidines was synthesized and their antimicrobial activity was evaluated in vitro against eight potentially pathogenic strains of fungi. Compounds with an alkylsulfanyl substitution have antifungal activity, which improves with increasing length of the aliphatic chain.

Chemical composition of the hydrodistilled volatile fraction from flowers of four Staphylea L. species (Staphylea colchica Stev., Staphylea elegans Zab., Staphylea holocarpa Hemsl., Staphylea pinnata L.) was determined by the GC/MS method. Compounds in fresh and dried flowers (stored for 1 year) were determined. Mostly, structures of different oxygenated aliphatic hydrocarbons in all four species were found. Different aldehydes, ketones, esters of higher fatty acids, and hexadecanoic acid were identified, with dominating content of tricosane, hexadecanoic acid and also of heneicosane, pentacosane, heptacosane, and nonacosane. In S. pinnata L. (fresh flowers) some nonaliphatic hydrocarbons, and in S. holocarpa Hemsl. (fresh flowers) esters of higher fatty acids were found.