Biomedical subjects

Verónica Pino

Publications and source records attributed to Verónica Pino.

6 recordsLinked to original sources

PubMed2007

Micellar solid-phase microextraction for determining partition coefficients of substituted polycyclic aromatic hydrocarbons in micellar media: possible prediction of hydrocarbon-micelle behaviour.

Micellar solid-phase microextraction (MSPME) coupled to gas chromatography-mass spectrometry (GC-MS) has been used to obtain partition coefficients of a group of 18 substituted aromatic hydrocarbons to ionic and nonionic micelles. Statistical and factor analyses have been utilized to establish some general equations relating molecular descriptors of non-substituted polycyclic aromatic hydrocarbons and their partition coefficients obtained by MSPME. The obtained equations have correlation coefficients higher than 0.94. They are used to predict hydrocarbon-micelle partition coefficients for a group of hydrocarbons with reported literature values giving a correlation coefficient of 0.98 and a standard deviation of the prediction of 0.182. The predictive model was also applied to substituted polycyclic aromatic hydrocarbons with partition coefficient values obtained by MSPME, with a 69% level of success.

Calibration↗

PubMed2006

Determination of solute partition behavior with room-temperature ionic liquid based micellar gas-liquid chromatography stationary phases using the pseudophase model.

The use of micelles in ionic liquid based gas-chromatography stationary phases was evaluated using equations derived for a "three-phase" model. This model allows the determination of all three partition coefficients involved in the system, and elucidates the micellar contribution to retention and selectivity. Four types of micellar-ionic liquid columns were examined in this study: 1-butyl-3-methylimidazolium chloride with sodium dodecylsulfate or dioctyl sulfosuccinate, and 1-butyl-3-methylimidazolium hexafluorophosphate with polyoxyethylene-100-stearyl ether or polyoxyethylene-23-lauryl ether. The partition coefficients were measured for a wide range of probe molecules capable of a variety of types and magnitudes of interactions. In general, most probe molecules preferentially partitioned to the micellar pseudophase over the bulk ionic liquid component of the stationary phase. Therefore, addition of surfactant to the stationary phase usually resulted in greater solute retention. It is also shown that the selectivity of the stationary phase is significantly altered by the presence of micelles, either by enhancing or lessening the separation. The effects of surfactant on the interaction parameters of the stationary phase are determined using the Abraham solvation parameter model. The addition of sodium dodecylsulfate and dioctyl sulfosuccinate to 1-butyl-3-methylimidazolium chloride stationary phases generally increased the phase's hydrogen bond basicity and increased the level of dispersion interaction. Polyoxyethylene-100-stearyl ether and polyoxyethylene-23-lauryl ether surfactants, however, enhanced the pi-pi/n-pi, polarizability/dipolarity, and hydrogen bond basicity interactions of 1-butyl-3-methylimidazolium hexafluorophosphate to a greater degree than the ionic surfactants with 1-butyl-3-methylimidazolium chloride. However, these nonionic surfactants appeared to hinder the ability of the stationary phase to interact with solutes via dispersion forces. Therefore, it is possible to effectively predict which analytes will be most highly retained by these micellar-ionic liquid stationary phases.

Chromatography, Gas↗

PubMed2006

Theory and use of the pseudophase model in gas-liquid chromatographic enantiomeric separations.

The theory and use of the "three-phase" model in enantioselective gas-liquid chromatography utilizing a methylated cyclodextrin/polysiloxane stationary phase is presented for the first time. Equations are derived that account for all three partition equilibria in the system, including partitioning between the gas mobile phase and both stationary-phase components and the analyte equilibrium between the polysiloxane and cyclodextrin pseudophase. The separation of the retention contributions from the achiral and chiral parts of the stationary phase can be easily accomplished. Also, it allows the direct examination of the two contributions to enantioselctivity, i.e., that which occurs completely in the liquid stationary phase versus the direct transfer of the chiral analyte in the gas phase to the dissolved chiral selector. Six compounds were studied to verify the model: 1-phenylethanol, alpha-ionone, 3-methyl-1-indanone, o-(chloromethyl)phenyl sulfoxide, o-(bromomethyl)phenyl sulfoxide, and ethyl p-tolylsulfonate. Generally, the cyclodextrin component of the stationary phase contributes to retention more than the bulk liquid polysiloxane. This may be an important requirement for effective GC chiral stationary phases. In addition, the roles of enthalpy and entropy toward enantiorecognition by this stationary phase were examined. While enantiomeric differences in both enthalpy and entropy provide chiral discrimination, the contribution of entropy appears to be more significant in this regard. The three-phase model may be applied to any gas-liquid chromatography stationary phase involving a pseudophase.

Arylsulfonates↗

PubMed2005

Study of the interactions between phenolic compounds and micellar media using micellar solid-phase microextraction/gas chromatography.

Solid-phase microextraction coupled to gas-chromatography with mass-spectrometry detection has been employed to establish the sensitivity indexes as well as to study the partition coefficients of phenols into ionic and nonionic micelles. The sensitivity indexes values can be used to estimate qualitatively the affinity between phenols and micelles. The studied phenols, some of them with high environmental interest, include chloro-, alkyl-, and methoxy-phenols. The results obtained in this work, using 85 microm polyacrylate fiber and anionic (sodium dodecyl sulphate), cationic (cetyltrimethylammonium bromide), and nonionic (Triton X-100 and polyoxyethylene-10-lauryl ether) surfactants, indicate that SPME is a viable method for estimating the micelle partition coefficients.

Chromatography, Gas↗

PubMed2004

Solid-phase microextraction coupled to gas chromatography/mass spectrometry for determining polycyclic aromatic hydrocarbon-micelle partition coefficients.

Solid-phase microextraction (SPME) coupled to gas chromatography with MS detection has been employed to study the partition coefficients of PAHs to ionic and nonionic micelles. The results obtained in this work for seven PAHs, using 85-microm polyacrylate- and 100-microm poly(dimethylsiloxane)-coated fibers and anionic (sodium dodecyl sulfate), cationic (cetyltrimethylammonium bromide), and nonionic (polyoxyethylene-10-lauryl ether) surfactants, indicate that SPME is a viable method for estimating the partition coefficients of PAHs to micelle. The procedure could also be potentially extended to the measurement of partition coefficients between a wide variety of semi- or nonvolatile compounds and micellar media.

Anions↗

PubMed2003

Surfactant solvation effects and micelle formation in ionic liquids.

The formation of micelles in 1-butyl-3-methyl imidazolium chloride (BMIM-Cl) and hexafluorophosphate (BMIM-PF6) were explored using different surfactants and the solvation behavior of the new micellar-ionic liquid solutions examined using inverse gas chromatography.

Chromatography, Gas↗