Development of a stability-indicating HPLC method of etifoxine with characterization of degradation products by LC-MS/TOF, 1H and 13C NMR.

This paper describes a new LC-MS/TOF method for the degradation products determination when Etifoxine (ETI) is submitted to different stress conditions. Chromatography is performed by using Kromasil C18 column (250mm×4.6mm, 5μm particle size).

Effect of the chain length on the thermal and analytical properties of laterally biforked nematogens.

Three laterally substituted liquid crystals were synthesized in order to investigate the effect of a lateral biforked chain on the thermal and analytical properties. The mesogenic molecules have the same core containing four aromatic rings connected by two ester and one diazo linkages, they differ by the length of one chain within the lateral biforked substituent. The phase transition temperatures were obtained by polarized light microscopy and differential scanning calorimetry (DSC).

General contribution of nonspecific interactions to fluorescence intensity.

Many chemical compounds, including nonfluorescent ones, induce changes in the fluorescence spectra of certain probes, such as berberine cation and Reichardt's betaine, both in the absence and the presence of solvent, that affect almost exclusively emission intensity. In this work, the application of fluorescence detection by intensity changes (FDIC) to HPLC and TLC chromatographic systems with fluorescence detectors has been studied. FDIC detection is of special interest in detecting nonfluorescent analytes, either in HPLC or in TLC mode.

Solid phase extraction and liquid chromatographic determination of sildenafil and N-demethylsildenafil in rat serum with basic mobile phase.

HPLC method for the determination of sildenafil and its metabolite (N-demethylsildenafil) in rat serum has been developed. The technique included a solid phase extraction of the serum samples on a [poly(divinylbenzene-co-N-vinylpyrrolidone)] solid phase extraction sorbent. After conditioning, the cartridge was loaded with 0.

Analytical performances of two liquid crystals and their mixture as stationary phases in capillary gas chromatography.

Comparative gas chromatographic applications of two new liquid crystals called LCa and LCb and their equimolar mixture LC(a+b) were investigated. The thermal properties of LCa, LCb and LC(a+b) were established with differential scanning calorimetry (DSC) and polarizing microscopy. Differential scanning calorimetry of LC(a+b) showed that the melting or clearing temperature was intermediate between the corresponding temperatures of the pure compounds.