New frontiers and cutting edge applications in ultra high performance liquid chromatography through latest generation superficially porous particles with particular emphasis to the field of chiral separations (original) (raw)
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Analytical Chemistry, 2015
A variety of brush-type chiral stationary phases (CSPs) were developed using superficially porous particles (SPPs). Given their high efficiencies and relatively low back pressures, columns containing these particles were particularly advantageous for ultrafast "chiral" separations in the 4−40 s range. Further, they were used in all mobile phase modes and with high flow rates and pressures to separate over 60 pairs of enantiomers. When operating under these conditions, both instrumentation and column packing must be modified or optimized so as not to limit separation performance and quality. Further, frictional heating results in axial thermal gradients of up to 16°C and radial temperature gradients up to 8°C, which can produce interesting secondary effects in enantiomeric separations. It is shown that the kinetic behavior of various CSPs can differ from one another as much as they differ from the well-studied C18 reversed phase media. Three additional interesting aspects of this work are (a) the first kinetic evidence of two different chiral recognition mechanisms, (b) a demonstration of increased efficiencies at higher flow rates for specific separations, and (c) the lowest reduced plate height yet reported for a CSP.
Journal of Chromatography A, 2012
In this study two types of silica particles, one fully porous and the other superficial porous (core-shell or fused-core) were modified with a polysaccharide-type chiral selector and evaluated for the separation of enantiomers in nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC). The major goal of this project was to critically evaluate the contribution of the "flow through particles" to enhancing peak efficiency in CEC compared to nano-LC. The better performance of fused-core silica particles compared with silica particles of comparable size but having through pores questions the previous assumption that "flow through particles" is the major contributor to enhancing peak efficiencies observed in CEC. In addition, based on the results of this study it is suggested that contrary to previous reports on core-shell particles behaving poorly in narrow bore columns, these materials are quite suitable for CEC, at least in capillary columns of 100 m I.D.
Journal of chromatography. A, 2017
To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core(®), core shell or porous shell) particles with very large (1000Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications.
Journal of Chromatography A, 2020
Column selection often centers on the identification of a stationary phase that increases resolution for a certain class of compounds. While gains in resolution are most affected by selectivity of the stationary phase or modifications of the mobile phase, enhancements can still be made with an intentional selection of the packing material's microstructure. Unrestricted mass transfer into the particle's porous structure minimizes band broadening associated with hindered access to stationary phase. Increased efficiency, especially when operating above the optimal flow rates, can be gained if the pore size is significantly larger than the solvated analyte. Less studied are the effects of reduced access to pores due to physical hindrance and its impact on retention. This article explores the relationship between pore size and reversed phase retention and specifically looks at a series of particle architectures with reversed phase and size exclusion modes to study retention associated with access to stationary phase surface area.
Journal of Chromatography A, 2014
The challenges in HPLC are fast and efficient separation for a wide range of samples. Fast separation often results in very high operating pressure, which places a huge burden on HPLC instrumentation. In recent years, core-shell silica microspheres (with a solid core and a porous shell, also known as fused-core or superficially porous microspheres) have been widely investigated and used for highly efficient and fast separation with reasonably low pressure for separation of small molecules, large molecules and complex samples. In this review, we firstly show the types of core-shell particles and how they are generally prepared, focusing on the methods used to produce core-shell silica particles for chromatographic applications. The fundamentals are discussed on why core-shell particles can perform better with low back pressure, in terms of van Deemter equation and kinetic plots. The core-shell particles are compared with totally porous silica particles and also monolithic columns. The use of columns packed with core-shell particles in different types of liquid chromatography is then discussed, followed by illustrating example applications of such columns for separation of various types of samples. The review is completed with conclusion and a brief perspective on future development of core-shell particles in chromatography.
Effect of particle size distribution on the separation efficiency in liquid chromatography
2014
In this work, the influence of the width of particle size distribution (PSD) on chromatographic efficiency is studied. The PSD is described by lognormal distribution. A theoretical framework is developed in order to calculate heights equivalent to a theoretical plate in case of different PSDs. Our calculations demonstrate and verify that wide particle size distributions have significant effect on the separation efficiency of molecules. The differences of fully porous and core-shell phases regarding the influence of width of PSD are presented and discussed. The efficiencies of bimodal phases were also calculated. The results showed that these packings do not have any advantage over unimodal phases.
Core-shell particles lead the way to renewing high-performance liquid chromatography
TrAC Trends in Analytical Chemistry, 2015
In this review, we present the latest highlights and trends in the use of core-shell particles as stationary phases in columns for liquid chromatography (LC). These highly homogeneous particles have a diameter of 1.3-5 μm with a solid silica core and a porous surface that make their performance excellent compared to fully-porous particles. Use of these columns has been growing exponentially since their first largescale manufacture in 2006, and they are an emerging trend in the analysis of biological, toxicological and pharmaceutically interesting compounds. We review the main theoretical aspects responsible for their surprisingly good chromatographic behavior and analytical features. We also summarize state-ofthe-art analytical applications taking advantage of this column technology that is leading the current revolution in LC.
Journal of chromatography. A, 2014
Fast chiral supercritical fluid chromatography (SFC) separations have become important due to 12 the increasing use of high throughput experimentation (HTE) in organic synthesis. These HTE 13 experiments can generate hundreds of samples for chiral analysis that need to be assayed in a 14 short time. In general, chiral SFC can provide much faster analysis times compared to liquid 15 chromatography (LC). Additionally, columns packed with smaller particles can provide faster 16 and more efficient separations. In this study, the effect of the particle size on the speed and 17 resolution of chiral separations by SFC was evaluated. The performance of Chiralcel OD 18 columns packed with either 5 µm or 3 µm particles were compared using van Deemter and other 19 kinetic plots. The results clearly illustrate the benefits of using smaller particle stationary phases 20 for improved speed and chiral chromatographic performance by SFC.
Analytical and Bioanalytical …, 2010
The characterization of mass-transfer processes in a chromatographic column during a separation process is essential, since the influence of the mass-transfer kinetics on the shape of the chromatographic band profiles and on the efficiency of the separation is crucial. Several sources of mass transfer in a chromatographic bed have been identified and studied: the axial dispersion in the stream of mobile phase, the external mass-transfer resistance, intraparticle diffusion, and the kinetics of adsorptiondesorption. We measured and compared the characteristics and performance of a new brand of shell particles and those of a conventional brand of totally porous silica particles. The shell stationary phase was made of 2.7-µm superficially porous particles (a 1.7-µm solid core is covered with a 0.5-µm-thick shell of porous silica). The other material consisted of totally porous particles of conventional 3.5-µm commercial silica. We measured the first and second central moments of the peaks of human insulin over a wide range of mobile phase velocities (from 0.02 to 1.3 mL/min) at 20°C. The plate height equations were constructed and the axial dispersion, external mass transfer, as well as the intraparticle diffusion coefficients were calculated for the two stationary phases.