title: Optimization of a solid-phase extraction protocol for fractionation of selected steroids using retention data from micro thin-layer chromatography.
abstract: In this paper a simple protocol is described for estimating of solid-phase extraction (SPE) elution volumes of steroids based on retention data generated from micro-planar chromatography. Particularly, the retention of selected steroids, including estrogens and progestagens, was studied on wettable with water octadecylsilica HPTLC plates and mobile phases composed of methanol:water mixtures ranging from 20 to 100% (v/v). It was found that TLC retention data can be linearized by plotting R(M) values of steroids against a reciprocal form of the organic modifier molar fraction (1/X(s)). Using such a mathematical approach, the retention parameter of steroids investigated could be easily back-calculated for a wide range of mobile-phase compositions, using few initial experimental data points. The hold-up time of SPE cartridges filled with 0.5 g of C-18 adsorbent was determined experimentally, and appropriate retention factor values (k(SPE)) for components of interest studied were calculated. Using an appropriate slope and intercept coefficients of the linear-regression equation formed as log k(SPE) = aR(M) + b, the steroids SPE elution volumes were predicted beyond the experimental data range that was available for a solid-phase extraction experiment, particularly for mobile phases that contained a high level of water.
authors.affiliation: Section of Toxicology and Bioanalytics, Department of Environmental Biology, Koszalin University of Technology, Poland. pkarz@wp.pl
authors.forename: Paweł K
authors.initials: PK
authors.lastname: Zarzycki
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Włodarczyk
authors.forename: Magdalena B
authors.initials: MB
authors.lastname: Zarzycka
authors.forename: Bronislaw K
authors.initials: BK
authors.lastname: Głód
mesh_terms: D053000:Analytic Sample Preparation Methods; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D000432:Methanol / Q000737:chemistry; D012044:Regression Analysis; D052616:Solid Phase Extraction / Q000379:methods*; D013256:Steroids / Q000737:chemistry / Q000302:isolation & purification*; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D013256:Steroids; D014867:Water; D000432:Methanol