Band 61, Heft 1

A method was described for simultaneous determination of nine organic heterocyclic pesticide residues by gas chromatography-mass spectrometry-selected ion monitoring. Atrazine, vinclozolin, procymidone, triflumizole, imazalil, buprofezin, propiconazole, fenarimol, and pyridaben were clearly separated from each other, extracted with acetone—hexane mixture, purified with graphitized carbon black cartridge and neutral Al2O3 cartridge, eluted with acetone—hexane mixture, simultaneously determined by GC-MS, and then quantified with an external standard method. Recoveries of pesticides ranged from 73 % to 116 % at the spiked level of 0.01–30 mg kg−1, while the relative standard deviation was between 3 % and 27 %. In addition, the limits of determination (0.01 mg kg−1 to 5.0 mg kg−1) and linearity (0.02–40 μg mL−1) revealed that simultaneous determination of multi-residues in Chinese teas (like Oolong tea, green tea, red tea, etc.) was possible. Furthermore, an interlaboratory study among 5 labs was conducted to further validate the method, and the results were satisfactory.

The influence of CCl4 on the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), the value of the total antioxidant status (TAS), and the concentration of malonic dialdehyde (MDA) and glutathione (GSH) was monitored in plasma or whole blood of rabbits. The administration of CCl4 caused the increase of the SOD activity to approximately 150 % and the decrease in the activity of GPx and GR by about 50 %. These changes were accompanied with the increase in TAS value and MDA concentration and the decrease of GSH concentration. The effect of CCl4 was suppressed by the previous 7 days lasting or simultaneous administration of vitamin E. Oxidative stress caused by CCl4 was accompanied by the development of reactive oxygen forms, especially superoxide radical anion.

The corroding process of six glasses of the Na2O-K2O-CaO-ZrO2-SiO2 system with ZrO2content 0–2.13 mass % by water was observed during static tests at 121°C and pressure of 0.25 MPa in steam sterilizer. Significant increase of Na+ and K+ content in leachates was observed after the addition of ZrO2 into glass. Further increase of the content of ZrO2 in glasses slowed down the rate of Na+ and K+ leaching. The leaching process of SiO2 as well as Na+, K+, and Ca2+ ions was evaluated on the basis of comparison with model leaching processes. Variation of the concentrations of Na+, K+, Ca2+, and SiO2 in leachates with time was described by empirical equation. Observed changes in the initial leaching rates of Na+, K+, Ca2+, and SiO2 can be ascribed to the content of ZrO2 in glasses. The presence of ZrO2 in glasses reduced the overall rate of glass dissolution.

Effect of the type and number of high-speed impellers installed on a common shaft on the power characteristics was investigated in water and glucose solutions of different concentration. Different configurations of the Rushton or Smith turbines, pitched blade turbines, propeller, and A 315 impeller were tested. Measurements of power consumption were carried out within the transitional and turbulent regime of the fluid flow using the strain gauge method. Baffled agitated vessels with inner diameter of 0.288 m and 0.634 m were used for the experiments. Liquid height in the vessels was equal to the vessel diameter or it was twice higher. The relative power consumption was compared for different configurations of the impellers.

The composting of organic solid waste, the mixture of fruit and vegetable leftovers enriched with night soil, was investigated in a closed thermally insulated reactor. It was found that 80.9 % of the original substrate biodegraded after 14 days. A mathematical model of the column reactor was proposed where the biodegradation rate of the organic solid waste was described using simple n-thorder kinetics. A good prediction of process performance was obtained using the proposed kinetics and experimentally obtained reaction heat.

The effect of ohmic and conventional heat processing of different food products on their chemical and physical parameters was studied. Depending on the food being analysed, parameters such as pH, total solids, ash, titratable acidity, ascorbic acid, total sugars, total fatty acids, total phenolic compounds, and anthocyanins content were determined before and after ohmic and conventional pasteurization techniques and the results were compared using one-way analysis of variance. In goat milk samples treated by ohmic technology the pH value (6.58) and total fatty acids content in milk fat (86.5 mass %) were comparable to those found in milk treated by conventional process, however, ohmically treated samples presented a lower content of lactic acid, 0.13 %. In cloudberry jam samples treated by ohmic technology the results of some of the main parameters tested, such as total sugar content 46.1 mass %, ascorbic acid content 2.83 mass %, and titratable acidity 6.01 mass % (as citric acid) did not show significant differences when compared with samples treated by conventional technology.

Direct synthesis of lead iodide, a promising material for X-ray and γ detectors operating at room temperature, was developed and optimized. The influence of admixture of rare earth elements Ce, Ho, Gd, Yb, Er, and Tb in concentrations 0.05–0.5 at. % on the quality of prepared PbI2 was investigated. Zone melting was employed in order to increase the lead iodide purity. Electrical and optical properties of PbI2 samples were assessed on the basis of the measurement of electrical resistivity and low-temperature photoluminescence. The electrical resistivity of synthesized samples varied from 109 Ω cm to 1011 Ω cm and occasionally it was increased up to 1013 Ω cm.

Simple catalytic systems for the Suzuki—Miyaura reaction of aryl chlorides under microwave conditions were tested. Microwave irradiation facilitated the reaction course. The catalyst, base, and solvent effect were studied and two reaction systems offered reasonable to high yields within a short time.

The extraction of a coal-tar pitch with supercritical carbon dioxide was performed under optimal pressure, flow rate, and three different constant temperatures. The extraction kinetics was examined for each temperature and it was surprisingly found that the extraction rate of most components was governed by the first-order kinetics. It was assumed that this deviation from typical models of supercritical fluid extraction kinetics was caused by high pitch concentrations and low solubilities of the components.

A photocatalytic film reactor with a titanium dioxide film was used for oxidation of gaseous ethanol at 253.7 nm. The influences of partial pressures of oxygen and water vapour in different carrier gases were studied. The rate of photocatalytic oxidation of ethanol was significantly affected by the content of oxygen but water vapour had no effect. It was suggested that the photocatalytic transformation of ethanol follows a direct oxidation mechanism where the interaction of ethanol with positive hole gives first cationic free radical of ethanol, which is converted by multipathway reactions with oxygen to acetaldehyde, ethyl formate, and ethyl acetate.

The kinetics and mechanism of hydroboration of oct-1-and-4-ene with a series of dimeric dialkylboranes was investigated. The kinetic results showed that the hydroboration of terminal olefins proceeds via a three-halves-order mechanism, first-order with respect to the olefin and one-half-order with respect to the dimer. Using dicyclohexylborane, diisopinocamphenylborane, and 3,6-dimethylborepane the observed rate constants for the hydroboration of oct-4-ene were approximately 6 times smaller than those for oct-1-ene. Supporting computations showed that both steric and electronic effects influence the rate of hydroboration of both internal and terminal olefins. A model computational study of the isomerization of oct-4-ene with di(prop-2-yl)borane showed that formation of the terminal hydroborated complex is thermodynamically favored over the internal complex.

The geometries of N,N′-diphenylbenzene-1,4-diamine (DPPD), N-phenyl-N′-(1-phenylethyl)benzene-1,4-diamine (SPPD), N-(4-methylpentan-2-yl)-N′-phenylbenzene-1,4-diamine (6PPD), N-propan-2-yl-N′-phenylbenzene-1,4-diamine (IPPD), N-(2-methoxybenzyl)-N′-phenylbenzene-1,4-diamine (MBPPD), and N-phenyl-N′-(2-phenylpropan-2-yl)benzene-1,4-diamine (CPPD) as well as of their dehydrogenation products were optimized by the semiempirical AM1 method. The results support the idea of stable NB=CX structures formation during the consecutive dehydrogenation of SPPD, 6PPD, IPPD, and MBPPD antioxidants. The biradicals formed during the second step of dehydrogenation of substituted phenylenediamines might be important for their antioxidant effectiveness.

Formation of tetracyanoethylene—benzene 1: 1 and 1: 2 complexes was modeled using the Møller—Plesset second-order theory (MP2) and polarized continuum model (PCM). The MP2 calculated geometry of 1: 1 complex presents a plane-parallel C 2υ sandwich structure with interplanar distance 3.05 × 10−10 m, while the 1: 2 complex has D 2h geometry where the planparallel distance is equal to 3.09 × 10−10 m. The MP2 calculations indicate that the main part of formation enthalpy in both complexes is dispersion energy due to intermolecular electron correlation. The calculations also show that the formation entropy destabilizes both complexes since from the two constituent molecules one complex molecule arises. The MP2/6-31G* procedure showed to be a suitable tool for the estimation of the relative importance of 1: 2 complexation compared to the 1: 1 complexation. In the gas phase the ratio of the equilibrium constants of both complexes K 1:2/K 1:1 = 0.09 was calculated. The presence of solvent, treated by the PCM, further destabilized the 1: 2 complex with respect to the 1: 1 complex. The ratio K 1:2/K 1:1 in CH2Cl2 calculated by the PCM method was 0.022, i.e. the 1: 2 complex was almost 50 times less stable than the 1: 1 complex, which is in agreement with available experimental data. According to the calculations, solvent always destabilizes complex with respect to the isolated (solvated) components. It was also found that charge polarization in the 1: 2 complex with respect to that in the 1: 1 complex was not strictly additive due to the presence of the second benzene molecule in the 1: 2 complex. Non-additive were also formation enthalpy, entropy, polarizability, charge transfer from donors to acceptor molecule and other properties. This fact is caused by a slightly changed interaction between constituent molecules in the 1: 2 complex in comparison with the 1: 1 complex as well as by the interaction between benzene molecules in the 1: 2 complex which is missing in the 1: 1 complex. Preliminary CIS/6-31G* theoretical study regarding a few first-electron (electron charge transfer) transitions in both complexes indicates the presence of Frenkel excitn and Davydov transition energy splitting in the 1: 2 “supercomplex” with the first allowed π → π* absorption transition at λ = 355 nm, while the first allowed transition in the case of 1: 1 complex was characterized by λ = 392 nm with the oscillator strength only half of that of the 1: 2 complex, which is in agreement with experiment. These unexpected large hypso-and hypochromic effects predicted by the theory could allow to overcome difficulties of the experimental determination of the 1: 2 complexation.