title: Analysis of ecdysteroids by micellar electrokinetic chromatography with on-line preconcentration.
abstract: In order to enhance the UV detection sensitivity, an application study of an on-line preconcentration technique for micellar electrokinetic chromatographic (MEKC) was carried out. The simultaneous determination of four test ecdysteroids, 20-hydroxyecdysone, ajugasterone C, polypodine B and ponasterone A has been investigated by using the normal stacking mode in MEKC with UV detection. The effects of anionic surfactant composition and concentration, the applied voltage, the pH buffer, the kind and the amount of organic solvent and the injection time on the analyte resolution were evaluated. The optimised conditions for the separation involved the use of a 50 mM borate as the running buffer containing 50 mM of a mixture of sodium dodecyl sulphate (SDS) and sodium cholate (SC) in the ratio of 1:1 together with a concentration of 10% (v/v) of 2-PrOH at pH 9.0. Hydrodynamic injection of 12 s at 50 mbar and separation voltage of 20 kV at temperature of 20 degrees C were employed. These conditions allowed a repeatability separation within 21 min. Concentration detection limit for the neutral analytes studied improve about an order of magnitude. The method was also applied to the determination of ecdysteroids in a real sample.
authors: Dipartimento di Scienze Farmaceutiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy. santagat@unict.it
authors: Natale Alfredo
authors: NA
authors: Santagati
authors: Salvatore
authors: S
authors: Tropea
authors: Giuseppe
authors: G
authors: Ronsisvalle
mesh_terms: D027703:Amaranthaceae / Q000737:chemistry; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D026461:Ecdysteroids / Q000032:analysis* / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D010936:Plant Extracts / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020358:Sodium Cholate; D012967:Sodium Dodecyl Sulfate; D012997:Solvents; D013501:Surface-Active Agents; D013657:Taurodeoxycholic Acid
chemical_list: D026461:Ecdysteroids; D010936:Plant Extracts; D012997:Solvents; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D013657:Taurodeoxycholic Acid; D020358:Sodium Cholate