Oil-in-Water Type Microemulsion Electrokinetic Chromatography for the Analysis of Corticosteroids
Date Issued
2006
Date
2006
Author(s)
Wu, Chi-Hung
DOI
zh-TW
Abstract
Generally microemulsion electrokinetic chromatography (MEEKC) using SDS as surfactant was difficult to separate neutral, highly hydrophobic and structure-related corticosteroids. In this study, for better understanding of the microemulsion property, dithizone was used as an index to measure the absorbance of various compositions of oil, surfactant, cosurfactant and aqueous buffer.Therefore the pseudoternary phase diagram could be constructed. Hereafter we found at the condition of 0.8% (w/w) n-octane, 3.6% (w/w) SDS, 6.6% (w/w) 1-butanol, 89% (w/w) 40 mM phosphate buffer (pH 8.0), and applied voltage of + 7 kV, six corticosteroids including, prednisone (Ps), hydrocortisone (H), hydrocortisone acetate (HA), prednisolone (P), prednisolone acetate (PA), and cortisone acetate (CA) could be completely separated. But the higher SDS concentration resulted in longer retention time. Even by the addition of organic modifier, the separation could not be improved. To reduce SDS content used we turned to use diethyl L-tartrate having less surface tension as oil phase. Under the microemulsion compositions of 0.5% (w/w) diethyl L-tartrate, 1.7% (w/w) SDS, 1.2% (w/w) 1-butanol, 89.6% (w/w) 40 mM phosphate buffer (pH 8.0), 7% (w/w) ACN, and applied voltage of + 10 kV, ten structure-related steroids including Ps, H, HA, P, PA, CA and aldosterone (A), dexamethasone (D), triamcinolone (T), and triamcinolone acetonide (TA) could be completely baseline separated. This indicates that SDS-containing microemulsions also have good selectivity for corticosteroids. The reproducibility of the retention time (N=4) for most of the compounds was less than 0.8% except that for T, Ps, and A. The average theoretical plate was 18800 m-1. To evaluate the validation of the system, corticosteroids in urine was also studied. It was demonstrated that the developed method was highly promising in the clinical analysis of these compounds.
Subjects
微乳液
微乳液電動層析
皮質類固醇
陰離子界面活性劑
Microemulsion
Microemulsion electrokinetic chromatography
MEEKC
Corticosteroids
Type
thesis