Optimized separation of seven corticosteroids by micellar electrokinetic chromatography

Abstract

The corticosteroids studied can be effectively separated by employing micellar electrokinetic capillary chromatography (MECC). The effect of pH, borate concentration and the sodium dodecyl sulfate (SDS) concentration on both the resolution and the selectivity was studied under 15 different experimental conditions. The experimental design was similar to the central composite design approach. Empirical quadratic regression models were derived for analyte migration time, band broadening and analyte velocity. Satisfactory regression fits and coefficients of determination for prediction were obtained with cross-validated models. The models for analyte migration time and analyte velocity were in good agreement with theory. Modeling of the band broadening seemed to be somewhat more complicated. Optimum conditions for resolution and selectivity were different. This is due to the fact that selectivity studies ignore the electroosmotic and band broadening properties of different electrolyte solutions. However, the study of the selectivity yielded good information about the suitability of the electrolyte systems for the particular separation problem. Although a high solubilizing power of SDS caused the corticosteroids to partition strongly into the SDS micelles, a good separation could be achieved at low SDS concentrations.

Optimization of selectivity and resolution in micellar electrokinetic capillary chromatography with a mixed micellar system of sodium dodecyl sulfate and sodium cholate

“…The first biological (organic) buffer that we investigated was MOPS, which is effective in the pH range 6.5-7.9. Although the MOPS-SDS-SC system gave good separations of the corticosteroids [24], it was not optimal because we recognized that the separation of the corticosteroids was better at pH values around nine, which is in accordance with many other studies [5, . To ensure that the buf- fering capacity would really work we had to choose another buffer.…”

Micellar electrokinetic chromatography for simultaneous determination of six corticosteroids in commercial pharmaceuticals

“…Cai and El Rassi introduced neutral surfactants to form complexes with anionic borates through the association of polyhydroxy groups under alkaline conditions [6]. Some MEKC methods have used bile salts to analyze corticosteroids, these include a study by Jumppanen and Wiedmer et al who used borate and SDS to optimize separation [7], and one by Wiedmer et al, who used [(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxy-propanesulfonic acid, sodium cholate, and SDS for serum applications [5]. Bumgarner and Khaledi used phosphate, borate, and/or alkyl sulfonates with SDS and acetonitrile or sodium taurocholate and sodium glycodeoxycholate to examine the influence of the number of hydroxyl functional groups on the steroidal backbone of the bile salts [8,9].…”

Retention modeling and resolution optimization for a group ofN‐phenylpyrazole derivatives in micellar electrokinetic chromatography using empirical and physicochemical models

“…As an example, it can be cited the overlapping resolution mapping (ORM) [3][4][5][6][7][8][9], iterative regression strategies [10], physicochemical approaches [11][12][13][14], empirical equations [15][16][17][18], and artificial neural networks (ANNs) [19]. In order to carry out these studies, several designs can be used, e.g., the Plackett-Burman design [20,21] and the orthogonal array design (OAD) [22] which are factorial designs suitable for screening the influence of many parameters and to monitor possible interactions among a large number of factors, or the central composite design [23,24] that can provide a response surface for the prediction of areas of optimum performance. From the different strategies cited, the ORM has been one of the most used [3][4][5][6][7][8][9] because it allows the deduction of the optimal separation conditions from an overlay of all the graphs obtained plotting the resolution versus different separation conditions.…”