title: Separation of steroids using vegetable oils in microemulsion electrokinetic capillary chromatography.
abstract: The steroids, hydrocortisone, androstenedione, 17-α-hydroxyprogesterone, testosterone, 17-α-methyltestosterone, and progesterone were separated with microemulsion electrokinetic chromatography (MEEKC) and detected with UV absorption. The microemulsion phases were prepared from both artificial and vegetable oils, from them the first was made of alkane and alcohol and the latter from colza, olive, linseed, and walnut oils. The electrolyte solutions were made to emulsions using sodium dodecyl sulfate and alkaline tetraborate. The solution mixtures made from ethyl acetate, sodium dodecyl sulfate, 1-butanol, acetonitrile, and sodium tetraborate were used as the reference solutions to evaluate the performance of the vegetable oil emulsions. Our study showed that the lipophilic organic phase in the microemulsion did provide resolution improvements but not selectivity changes. The results also correlate with real interactions of the steroids with the lipophilic organic microemulsion phase. The quality of the oils between the manufacturers did not have importance, which was noticed from the equal behavior of the steroids in the vegetable oil emulsions. Detection limits of the steroids in vegetable oil emulsions were at the level of 0.20-0.43μg/L. Thus, they were 2-10 times higher than the concentrations in the partial filling micellar electrokinetic chromatography (PF-MEKC), which we have obtained earlier. The repeatability (RSD%) of the electrophoretic mobilities of the steroids was between 0.50 and 3.70. The RSD% values between the inter-day separations were below 1%, but when walnut and olive oils were used the values exceeded even 10%.
authors.affiliation: Lappeenranta University of Technology, LUT Chemistry, Laboratory of Chemistry, P.O. Box 20, FI 53851 Lappeenranta, Finland. Electronic address: heli.siren@lut.fi.
authors.forename: Heli
authors.initials: H
authors.lastname: Sirén
authors.affiliation: Lappeenranta University of Technology, LUT Chemistry, Laboratory of Chemistry, P.O. Box 20, FI 53851 Lappeenranta, Finland.
authors.forename: Sari
authors.initials: S
authors.lastname: Vesanen
authors.affiliation: Finnish Food Safety Authority Evira, Research and Laboratory Department, Risk Assessment Research Unit, Mustialankatu 3, FI 00790 Helsinki, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Suomi
mesh_terms: D000085:Acetates / Q000737:chemistry; D000097:Acetonitriles / Q000737:chemistry; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004655:Emulsions / Q000737:chemistry*; D057230:Limit of Detection; D010938:Plant Oils / Q000737:chemistry*; D015203:Reproducibility of Results; D013256:Steroids / Q000032:analysis / Q000302:isolation & purification*
chemical_list: D000085:Acetates; D000097:Acetonitriles; D004655:Emulsions; D010938:Plant Oils; D013256:Steroids; C007650:ethyl acetate; C032159:acetonitrile
keywords: Capillary electrophoresis; Microemulsion; Separation; Steroid; Vegetable oils