Stationary phase monolithic

The most important feature of monolithic media is that the mobile phase flows exclusively through the separation unit. In contrast, there is no flow inside the conventional porous chromatographic particles and only a partial flow through the perfusion beads. Just as with the membrane adsorbers, monolith stationary phases may be operated with a minimum in mass transfer resistance with the concomitant advantages in terms of speed and throughput. 

In order to obtain improvement in fast separations for bioanalysis by HPLC-MS/MS, the use of monolithic stationary phases may be the way. 

Vegvari, A., and Guttman, A. (2006). Theoretical and nomenclatural considerations of capillary electrochromatography with monolithic stationary phases. Electrophoresis 27, 716—725. 

Neutral hydrophobic bulk monolithic stationary phase... 

Bedalr, M., and El Rassl, Z. (2003). Capillary electrochromatography with monolithic stationary phases III. Evaluation of the electrochromatographic retention of neutral and charged solutes on cationic stearyl-acrylate monoliths and the separation of water-soluble proteins and membrane proteins. /. Chromatogr. A 1013, 47-56. 

Ping, G. C., Zhang, W. B., Zhang, L. H., Schmitt-Kopplin, P., Zhang, Y. K., and Kettrup, A. (2003). Rapid separation of nucleosides by capillary electrochromatography with a methacrylate-based monolithic stationary phase. Chromatographia 57, 629-633. 

Since 1992, a vast variety of rigid organic monolithic stationary phases with different chanistry, functionality, and column geometry has been reported for HPLC as well as CEC applications, as summarized by the number of excellent reviews [25-32,213], The development and enhancanent of monolithic stationary phases is stiU a rapidly growing area of research with scientific and industrial interest. 

Monolithic stationary phases have to be regarded as the first substantial further development of HPLC columns, as they present a single particle separation medium, made up of porous polymer. As a consequence of their macroporous structure, they feature a number of advantages over microparticulate columns in terms of separation characteristics, hydrodynamic properties, as well as their fabrication ... 

Due to the fact that the polymer can chemically be attached to the column wall during polymerization, monolithic stationary phases do not necessitate frits to retain the column packing. 

Monolithic stationary phases do not possess interparticulate voids, which results in enhanced separation efficiency due to reduced band broadening. 

Dne to the macroporons strnctnre of monolithic stationary phases (flow channels), the solvent is forced to pass the entire polymer, leading to faster convective mass transfer (compared to diffnsion), which provides for analyte transport into and out of the stagnant pore liqnid, present in the case of microparticulate columns. 

Due to the fact that thermally initiated free radical copolymerization is by far the most routinely employed method for fabrication of organic monolithic stationary phases, the pore formation mechanism is discussed for this particular kind of polymerization. 

Absorbance signals seen in NIR consist of combination and overtone bands of hydrogen bonds such as C-H, N-H, 0-H, and S-H, which are aroused by large force constants and small mass. NIR spectra thus cover precious information on chemical as well as physical properties of analyzed samples due to characteristic reflectance and absorbance patterns [121-123], which makes this analysis method applicable to the characterization of monolithic stationary phases. 

Monolithic stationary phases as a comparatively young species of HPLC column can only be accepted as a serious alternative to particle-packed columns if column robustness is in the same order of magnitude than their microparticulate counterparts. 

A comprehensive survey of monolithic stationary phases that have been inttoduced in literature together with their key applications in separation science can be found in Table 1.1. 

Due to their defined monomodal macropore distribution (see Section 1.2.1), monolithic stationary phases, based on polymerization of organic precursors, are predestined for efficient and swift separation of macromolecules, like proteins, peptides, or nucleic acids, as their open-pore structure of account for enhanced mass transfer due to convection rather than diffusion. In fact, most of the applications of organic monolith introduced and investigated in literature are directed to analysis of biomolecule chromatography [29]. 

Sinner and Buchmeiser prepared a new class of functionalized monolithic stationary phases (norbornene monoliths) by a ROMP process that tolerates a huge variety of functional monomers [69]. They used this approach in order to chemically attach (3-cyclodextrin onto the monomer prior... 

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