title: Narrow-bore core-shell particles and monolithic columns in the analysis of silybin diastereoisomers.
abstract: Two chromatographic narrow-bore columns, a novel 2.6 μm particle-packed Kinetex™ C18 core-shell (50×2.1 mm id) and monolithic Chromolith(®) FastGradient RP-18e (50×2 mm id), were evaluated for the analysis of diastereoisomers of the flavonolignans silybin and 23-O-acetylsilybin under isocratic conditions. The main advantages of the core-shell column are markedly higher efficiency (hmin =2.8 versus 5.6 for silybin A) and better peak symmetry. The Kinetex column exhibits only a slight change in the height equivalent of the theoretical plate with a higher linear velocity of the mobile phase. The monolithic column shows notably higher selectivity in terms of selectivity factor (1.21 versus 1.12) in the analysis of critical-pair of diastereoisomers (silybin A and silybin B) and enables shorter run duration (approx. twofold) together with lower backpressure. The resolution power was found to be comparable, but the Kinetex column required a higher pressure of the mobile phase that, together with the higher chance of clogging, can be a disadvantage in the separation of biological samples. Successful baseline separation of silybin diastereoisomers in real pharmaceutical sample on monolithic column was accomplished.
authors.affiliation: Institute of Microbiology, Centre of Biocatalysis and Biotransformation, Academy of Sciences of the Czech Republic, Prague, Czech Republic. marholp@gmail.com.
authors.forename: Petr
authors.initials: P
authors.lastname: Marhol
authors.forename: Radek
authors.initials: R
authors.lastname: Gažák
authors.forename: Petr
authors.initials: P
authors.lastname: Bednář
authors.forename: Vladimír
authors.initials: V
authors.lastname: Křen
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D012117:Resins, Synthetic / Q000737:chemistry*; D000077385:Silybin; D012838:Silymarin / Q000737:chemistry* / Q000302:isolation & purification; D013237:Stereoisomerism
chemical_list: D012117:Resins, Synthetic; D012838:Silymarin; D000077385:Silybin