INVESTIGADORES
TRIPODI Valeria Paula
capítulos de libros
Título:
Microemulsions as pseudo-stationary phases in electrokinetic chromatography: I. Estimation of physico-chemical parameters. II. Analysis of drugs in pharmaceutical and biofluidic matrices.
Autor/es:
VALERIA TRIPODI; SILVIA LUCANGIOLI
Libro:
"Microemulsions: Properties and Applications"
Editorial:
Taylor and Francis
Referencias:
Lugar: Boca Raton; Año: 2008; p. 501 - 525
Resumen:
Abstract Microemulsions are dispersed systems consisting of nanometer size droplets of an  inmiscible liquid, stabilized by surfactant and cosurfactant molecules. Microemulsions can be prepared as water droplets in an oil phase (W/O) or oil droplets in a water phase (O/W). Due to many potential advantages of microemulsions such as high stability, ability to interact with a wide range of hydrophobic and hydrophilic compounds, transparency and easy preparation, they have been used in capillary electrophoresis (CE) as pseudo-stationary phases in the electrokinetic chromatography (EKC) mode. CE is a powerful technique with relevant features of performance such as simplicity, versatility, very high resolution in short time of analysis and low cost of operation. CE has been applied in different modes: in EKC the mobile phase is normally an aqueous buffer and the pseudo-stationary phase can be micelles (MEKC), vesicles (VEKC), or microdroplets (MEEKC). O/W is the type of microemulsion commonly used in EKC prepared with different surfactants or biosurfactants like sodium dodecylsulfate or phosphatidylcholine,  co-surfactants like butanol, oils and buffers at different pHs values. Physico-chemical propierties of drugs such as hydrophobicity is used to understantd the relation between chemical structures and their biological behaviour related to the partitioning into lipid bilayers of biomembranes, bioavailability, and pharmacokinetic. Critical micelar concentration (CMC) is a fundamental parameter in the evaluation of the biological activity of compounds with detergent propriety. The traditional method known as shake-flask method to determine hydrophobicity is usually expressed by the thermodynamic 1-octanol-water partition coefficient (Pow) defined as the ratio of concentrations of a species in the two phases at equilibrium. This method is time consuming, tedious, requires highly pure compounds and it is not adequate for compounds with log Pow higher than 4. Many different techniques have been used for determination of hydrophobicity like potentiometric titulation, liquid chromatography, etc. and an alternative method such as capillary electrophoresis. In MEEKC, the mass partition coefficient is calculated from the retention factor (k´) by the determination of the electrophoretic mobilities of the compounds. MEEKC has also found extensive application in different fields of pharmaceutical analysis for the determination of drugs and their impurities in bulk material and pharmaceutical formulations and for the dosage of drugs in biological fluids.