Biomedical subjects

Olinda Favoino

Publications and source records attributed to Olinda Favoino.

4 recordsLinked to original sources

PubMed2004

Off-line coupling of non-aqueous reversed-phase and silver ion high-performance liquid chromatography-mass spectrometry for the characterization of rice oil triacylglycerol positional isomers.

The determination of the triacylglycerol (TAG) profile in real world matrices is rather difficult as these compounds present a complex composition and are characterized by similar physico-chemical properties. This investigation is based on the high-performance liquid chromatography (HPLC) multidimensional determination of the TAG profile in terms of TAG species and positional isomers in a rice oil sample. The off-line bi-dimensional system was attained through the coupling of non-aqueous reversed-phase HPLC and silver ion (Ag)-HPLC. The primary column eluate was fractionated and the fractions of interest were then injected onto the secondary column, allowing the separation of several TAG positional isomers, unresolved in the first dimension. Peak assignment was carried out by combining retention data with atmospheric pressure chemical ionisation (APCI) MS spectra information. The fatty acid distribution along the glycerol backbone, determined by Ag-HPLC, was confirmed through diglyceride ion ratios derived from APCI-MS analysis. Method validation, where both precision and accuracy were measured, was carried out in preliminary applications on standard compounds. The analytical results obtained show that rice oil TAGs follow a distribution which can be considered typical for vegetable oils.

Atmospheric Pressure↗

PubMed2004

Comprehensive two-dimensional normal-phase (adsorption)-reversed-phase liquid chromatography.

A comprehensive two-dimensional HPLC system has been developed. It is based on the use of a microbore silica column operated in normal-phase (adsorption) mode (NP) in the first dimension and a monolithic type C18 column operated in reversed-phase (RP) mode in the second dimension. The interface was a 10-port, 2-position valve equipped with two storage loops. The first column was operated at a flow rate of 20 microL/min in isocratic mode, while the monolithic column flow rate was 4 mL/min and was operated in gradient mode. The sample loops had a volume of 20 microL each, and the analysis time in the second dimension was 1 min. In this way, every fraction from the first dimension was transferred on-line to the second dimension switching the automated valve every minute. A photodiode array detector has been used after the secondary column. The use of normal- and reversed-phase mode in the two dimensions can be helpful in the separation of complex mixtures of a natural origin that contain uncharged molecules of comparable dimension, different in polarity and hydrophobicity. The use of a microbore column in the first dimension permits the injection of a small volume in the secondary column, making the transfer of incompatible solvents from the first to the second dimension possible. Since the mobile phase in the NP separation is always stronger than the mobile phase at the head of the secondary column operated in RP mode, the initial eluent strength is important in order to obtain an effective focusing of the sample. The use of a monolithic type column in the second dimension permits the performance of very fast analysis operating at higher flow rates without loss of resolution, due to a higher permeability and increased mass-transfer properties in comparison to conventional particulate columns. Due to the brief reconditioning time necessary for monolithic columns, repetitive gradients can be carried out, extending the field of application to mixtures that contain components with different polarities. The utility of the system has been demonstrated in the analysis of the oxygen heterocyclic fraction of cold-pressed lemon oil, made up of coumarins and psoralens. These components may contain hydroxyl, methoxyl, isopentenyl, isopentenyloxyl, and geranyloxyl groups and oxygen-containing modification of the terpenoid side-chain groups, such as epoxides or vicinal diol groups. The relative location of the components in the 2D plane varied in relation to their chemical structure and allowed positive peak identification. The UV spectra recorded with the photodiode array detector supplied additional information that was used for the characterization of the studied sample.

Adsorption↗

PubMed2004

Determination of anthocyanins and related components in red wines by micro- and capillary HPLC.

Anthocyanins and derived components of red wines were determined by microHPLC using a 1 mm ID HPLC column coupled on-line with an MS detector equipped with an ESI (ElectroSpray Ionisation) source. The use of microcolumn HPLC greatly enhanced detection performance, allowing direct identification of components present in the fraction. Nineteen anthocyanins were detected. Fifteen were identified, two were tentatively identified, and only the aglycon of the remaining two components was certainly identified. Six anthocyanin-derived pigments, supposedly formed during wine maturation, were also investigated and found in a wine sample. The analysis of red wine anthocyanins was also carried out by injecting a large sample volume onto a 0.32 mm ID HPLC column, using the column focusing technique, in order to decrease the limit of detection and quantification of components present in a very small amounts.

Anthocyanins↗

PubMed2004

Fast GC analysis with a 50 microm ID column: theory, practical aspects, and application to a highly complex sample.

This research focuses on the minimization of GC analysis times through the use of a 5 m x 0.05 mm ID x 0.05 microm (film thickness) column. Experimental minimum plate height (Hmin) and optimum linear velocity values were derived from standard compound applications, under various analytical conditions, and then related to classical chromatographic theory. Deviations from the latter are measured and discussed. Practical aspects linked to the use of such capillaries, such as column sample capacity and detector acquisition rates, are also considered. Furthermore, a fast, and what can be considered a very fast method, were applied to the separation of a fuel sample. Coefficients of variation of elution times and relative peak areas were calculated in the very fast application. All analytical results are compared with those obtained by conventional 0.25 mm ID column applications.

Journal Article↗