The non-catalytic synthesis of biodiesel (fatty acids methyl esters) from triglycerides and methanol proceeds at elevated pressures above 100 bar and temperatures above 523 K. Kinetic investigations of the system revealed an unusual behavior of the reaction rate constant with increasing temperature and pressure. In order to explain this phenomenon, the phase behavior of the triglycerides–methanol mixture was investigated. The phase equilibria of the binary system sunflower oil–methanol were measured at different temperatures between 473 and 503 K, and a range of pressures between 10 and 56 bar. The experimental data were correlated using the Peng–Robinson, Soave–Redlich–Kwong and Redlich–Kwong–Aspen equations of state and different mixing rules. The best results were obtained with the RK–ASPEN equation of state and the Van derWaals mixing rule (VdW), which were then used to calculate the distribution of the phases at pressures and temperatures usual for the non-catalytic synthesis of biodiesel under high pressures. The obtained data indicated a strong influence of the phase equilibria on the reaction kinetics.

vapor–liquid equilibria --- high pressure --- supercritical conditions --- binary interaction parameters --- biodiesel synthesis

A sensitive, selective, precise and stability-indicating, new high-performance liquid chromatographic method for the analysis of carvedilol both as a bulk drug and in formulations was developed and validated. As the method could effectively separate the drug from its degradation products, it can be employed as a stability-indicating one. The method was validated for linearity, selectivity, precision, robustness, LOD, LOQ and accuracy. The chromatographic separation was achieved on a Chromolit RP8e, 100 ´ 4.6 mm, analytical column. The mobile phase consisted of a mixture of acetonitrile and water (45:55, V/V) (pH 2.5), pH adjusted with formic acid. The absorbance was monitored with a UV detector at 280 nm and the temperature of the analyses was 40 °C. The flow rate was 0.5 mL/min. The linearity (r ³ 0.999), reproducibility (0.68–1.27 %) and recovery (99.71–101.58) were found to be satisfactory. This method enables the simultaneous determination of carvedilol and its degradation products, as well as stability.

carvedilol --- 4-hydroxycarbazole --- RP-HPLC --- stability

Pb1-xMnxTe crystals were obtained by the Bridgman method and PbTe1-xSx crystals were grown by the vapour–liquid–solid technique. The tructural properties of Pb1-xMnxTe (x £ 0.10) and PbTe1-xSx (x £ 0.05) were observed by X-ray powder diffraction analysis. The optical properties were studied by Raman spectroscopy as a function of temperature. Measurements on these samples of different composition gave information about the Mn and S position in the lattice (off-centering), their clustering and ordering, as well as of the influence of these processes on the crystal structure and properties. The model of phonon behaviour based on the Random Element Isodisplacement model was applied, and it was found that the phonons in PbTe1-xSx show a two-mode behaviour (each TO-LO mode pair of the end members degenerates to an impurity mode), while the Pb1-xMnxTe optical phonons have a ntermediate one-two-mode behaviour (the LO-mode frequency shifts continuously from PbTe to MnTe, while the other modes resemble the two-mode case).

lead manganese telluride --- lead telluride sulphide --- structural properties --- Raman spectroscopy

Flavonoids were analysed in the extracts of garden (Salvia officinalis L.) and glutinous (Salvia glutinosa L.) sage. Ultrasonic extraction (20 minutes at 40 °C) and classical maceration (6 h at room temperature) of the extractable substances from dried herbs and dried residual plant materials from which the essential oil had previously been removed by hydrodistillation were performed with petroleum ether, 70 % aqueous solution of ethanol and water. It was found that the extracts from both plants contained flavonoids, but their compositions were dependent of the plant species, the polarity of the extracting solvent and the extraction technique applied. Apigenin and its derivatives (e.g., apigenin 4'-methyl ether), scutellarein 6-methyl ether, isoscutellarein 8-methyl ether, luteolin and 6-OH-luteolin-6-methyl ether where distinctive for S. officinalis. Apigenin, luteolin, 6-OH-luteolin-6-methyl ether, kaempherol 3-methyl ether, kaempherol 3,7-dimethyl ether, quercetin 3,7,3'-trimethyl ether and quercetin 3,7,3',4'-tetramethyl ether were distinctive for S. glutinosa. The flavonoids were also detected in considerable quantities in the plant material from which the essential oils had been already removed. Hence, this industrial waste plant material might be further used as a source of the flavonoids.

garden sage --- glutinos sage --- Salvia officinalis L. --- Salvia glutinosa L. --- flavonoids --- ultrasonic extraction --- maceration