Małgorzata Tatarczak-Michalewska

Characterization of the cis/trans Isomerization of Resveratrol by High-Performance Liquid Chromatography

ABSTRACT trans-Resveratrol was evaluated in a stability study. Reverse-phase high-performance liquid chromatography with a diode array detector was used for the comparison of stressed and reference samples. Aqueous ethanolic solutions were examined under variable conditions. The following parameters were investigated: the time of storage, exposure to sunlight for up to 30 days, temperature from 5 to 80°C, pH from 2.9 to 10.2, trans-resveratrol concentrations from 0.5 to 100 mg L−1, and 3, 10, 20, and 50% ethanol. The cis/trans equilibrium position was significantly influenced by the resveratrol concentration. The trans-resveratrol isomer was stable only at solutions more concentrated than 25 mg L−1 that were stable for 30 days in a refrigerator or at room temperature protected from light. Degradation of no more than 10% was observed at temperatures lower than 50°C and pH values lower 7.43.

Determination of Alizarin Red S by Ionic Liquid-Based Extraction and High-Performance Liquid Chromatography

ABSTRACT Alizarin red S was extracted from aqueous media using an ionic liquid-based biphase system, including dipotassium hydrogen phosphate and 1-butyl-3-methyl-imidazolium chloride. The ionic liquid and kosmotropic salt concentrations were characterized for partitioning of the dye. The determination of alizarin red S was performed by high-performance liquid chromatography on a C18 column using 50% methanol and 20 mM phosphate buffer at pH 3 with external standard calibration from 20 to 100 mg/L. Spectrophotometric detection was performed at 255 nm. The limit of detection was 38.5 ng/mL. An extraction efficiency exceeding 95% was obtained. The key parameter to optimize the extraction efficiency and the preconcentration factor was the proportion of ionic liquid to the kosmotropic salt. An inverse relationship between the preconcentration factor and alizarin red S recovery was observed. The extraction efficiency increased with temperature by approximately 5% per 10°C.

Correlation of Metal and trans-Resveratrol Concentrations in Red Wine

ABSTRACT Red wine samples were analyzed for Al, Cu, Zn, and Pb by inductively coupled plasma–mass spectrometry following microwave digestion. trans-Resveratrol was determined by high-performance liquid chromatography with a diode array detector using a C18 column and 25% aqueous acetonitrile as the mobile phase. trans-Resveratrol was present at concentrations of 0.4863–1.1840 mg L−1 and the values were inversely proportional to the results for aluminum and copper.

HPLC Identification of Copper (II)-Trans-Resveratrol Complexes in Ethanolic Aqueous Solution.

Reversed-phase high-performance liquid chromatography assay with the diode array detector was applied for detection of trans-resveratrol complexes with copper (II). Two complexes with copper to resveratrol ratio 3:2 and 1:1 were identified in ethanolic-aqueous solutions in neutral and acidic conditions. The matrix-assisted laser desorption ionization-time of flight mass spectrometry was used for evaluation of complexes in eluate liquid fraction. The structures of complexes were modeled by Titan, Spartan and HyperChem software. The findings obtained satisfactorily explain the chromatographic data and could provide useful an additional data about these forms in which is present trans-resveratrol in wine (free and/or forming complex with copper).

Effective phospholipid removal from plasma samples by solid phase extraction with the use of copper (II) modified silica gel cartridges

The new sorbent for solid phase extraction (SPE), based on silica gel modified with a copper (II), was obtained and its application for phospholipids removal from the human plasma was tested. SPE column conditioning requirements, the volume of the plasma, the composition of the elution solvent were all established. The efficacy of the removal of phospholipids was compared for different methods such as standard protein precipitation or HybridSPE Phospholipid Ultra and HybridSPE-PPT. The sample clean-up was verified by mass spectrometry (MS) and by monitoring of chromatograms in the region between 190nm and 400nm. The Fourier Transform Infrared Spectroscopy FT-IR and confocal Raman microscopy were used to evaluating the silica gel modifications and to show the structure of lipids confined in the silica pores.

Fragmental Method KowWIN as the Powerful Tool for Prediction of Chromatographic Behavior of Novel Bioactive Urea Derivatives

A series of the new urea derivatives with antinociceptive activity has been chromatographically evaluated using reversed phase materials: Zorbax Extend-C18, Cogent UDC Cholesterol with organic-aqueous eluent systems with two organic modifiers (methanol and acetonitrile). The chromatographic lipophilicity parameters: log kw, S and φ0 were determined basing on linear relationship between log k values and concentration of organic mobile phase modifier. The structure-retention studies revealed that the retention mechanism for all studied urea derivatives is uniform for the proposed chromatographic systems. However, a few exceptions were noticed. Derivatives containing nonpolar substituents in the imidazole ring acted as outliers for cholesterol column. In turn, the derivative containing ester polar substituent acted as an outlier in conventional reversed-phase system. Quantitative relationships based on a wide set of established computational molecular descriptors and experimental chromatographic data were also developed. Through a systematic study, by using the principal component analysis, fragmental method KowWIN appeared to be the most powerful software to produce reliable estimations of experimental retention parameters obtained on cholesterol column.

Adsorption Kinetics at Silica Gel/Ionic Liquid Solution Interface

A series of imidazolium and pyridinium ionic liquids with different anions (Cl−, Br−, BF4−, PF6−) has been evaluated for their adsorption activity on silica gel. Quantification of the ionic liquids has been performed by the use of RP-HPLC with organic-aqueous eluents containing an acidic buffer and a chaotropic salt. Pseudo-second order kinetic models were applied to the experimental data in order to investigate the kinetics of the adsorption process. The experimental data showed good fitting with this model, confirmed by considerably high correlation coefficients. The adsorption kinetic parameters were determined and analyzed. The relative error between the calculated and experimental amount of ionic liquid adsorbed at equilibrium was within 7%. The effect of various factors such as initial ionic liquid concentration, temperature, kind of solvent, kind of ionic liquid anion and cation on adsorption efficiency were all examined in a lab-scale study. Consequently, silica gel showed better adsorptive characteristics for imidazolium-based ionic liquids with chaotropic anions from aqueous solutions in comparison to pyridinium ionic liquids. The adsorption was found to decrease with the addition of organic solvents (methanol, acetonitrile) but it was not sensitive to the change of temperature in the range of 5–40 °C.