title: Possibilities of retention prediction in fast gradient liquid chromatography. Part 3: Short silica monolithic columns.
abstract: We studied possibilities of prediction of the gradient elution data for alkylbenzenes, flavones and phenolic acids on two short octadecyl silica gel monolithic columns, namely a Chromolith Flash C18, 25×4.6mm, and a "new generation" Chromolith High Resolution C18, 50×4.6mm, in fast 1-2min gradients. With fixed short gradient times and varying gradient ranges of acetonitrile concentration in water, high flow rates of the mobile phase (3-5mL/min) could be used. The gradient elution data were predicted from four gradient models based on two-parameter and three-parameter isocratic retention equations. Various gradient retention models can be used for prediction of chromatograms and optimization of separation within a fixed gradient time. A two-parameter log-log model introduced in 1974 and a three-parameter model introduced in 1980 provided slightly more accurate prediction than the Linear Solvent Strength (LSS) semi-logarithmic two-parameter model, most frequently used in reversed-phase LC. A three-parameter model introduced in 1978 provided slightly improved accuracy of prediction of gradient data with respect to two-parameter models, in contrast to another, more recent three-parameter empirical model introduced in 2010 (which failed for gradients starting at a non-zero concentration of acetonitrile). Both a longer (5cm) and more efficient Chromolith HR column and a shorter (2.5cm) slightly less efficient Chromolith Flash column provide useful separations in fast gradients (1-2min) at high flow rates (3.5-5mL/min), especially in second dimension of two-dimensional LC×LC, in combination with HILIC separation on monolithic microcolumn in D1.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemical, Technology, University of Pardubice, Studentská 573, 53210 Pardubice, Czech Republic. Electronic address: pavel.jandera@upce.cz.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jandera
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemical, Technology, University of Pardubice, Studentská 573, 53210 Pardubice, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Hájek
mesh_terms: D000097:Acetonitriles; D001555:Benzene Derivatives / Q000032:analysis; D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D047309:Flavones / Q000032:analysis; D015233:Models, Statistical; D012822:Silicon Dioxide / Q000737:chemistry*; D012997:Solvents; D014867:Water
chemical_list: D000097:Acetonitriles; D001555:Benzene Derivatives; D047309:Flavones; D012997:Solvents; C026679:octadecylsilica; D014867:Water; D012822:Silicon Dioxide; C032159:acetonitrile
keywords: Fast separations; Gradient elution; Modeling of chromatography; Monolithic columns; Two-dimensional chromatography