Monolithic supports, chromatography

He, B., Regnier, F., Microfabricated liquid chromatography columns based on collocated monolith support structures. J. Pharm. Biomed. Anal. 1998, 17, 925-932. 

Montes Sanchez F.J., Martin del Valle E.M., Galan M.A. and Cerro R.L. 2004. Modeling of monolith-supported affinity chromatography, Biotechnol. Prog., 20, 811. 

Despite the fact that the first silica monolithic supports have been already reported in the late 1970s, the first uniform porous silica rods used for reversed-phase chromatography... 

Although solid-phase chemistry traditionally has been performed in batch reactors, it can easily be implemented in a continuous-flow fashion (see [77] for a review), in analogy to the packed beds used in chromatography. Similarly to the current trend in HPLC, monolithic supports may replace the beads [77]. 

For example, our group developed a ROMP-based synthesis for these types of materials [68-74, 92-99] and described the use of these supports in heterogeneous catalysis [45, 98]. Since that time, numerous reviews have expounded the twenty-first century advancements in monolithic supports for separation science, heterogeneous catalysis, and tissue engineering [1, 100-114]. The published research from 2012 also includes the development of large-volume monolithic supports for biomolecule chromatography [115], boronate affinity chromatography columns [116], and monolith-supported Pt-based nanoparticles for hydrosilylation reactions [74]. 

The latest innovation is the introduction of ultra-thin silica layers. These layers are only 10 xm thick (compared to 200-250 pm in conventional plates) and are not based on granular adsorbents but consist of monolithic silica. Ultra-thin layer chromatography (UTLC) plates offer a unique combination of short migration distances, fast development times and extremely low solvent consumption. The absence of silica particles allows UTLC silica gel layers to be manufactured without any sort of binders, that are normally needed to stabilise silica particles at the glass support surface. UTLC plates will significantly reduce analysis time, solvent consumption and increase sensitivity in both qualitative and quantitative applications (Table 4.35). Miniaturised planar chromatography will rival other microanalytical techniques. 

Still, a lot needs to be done to develop large monolithic units, which would handle kilogram and larger production scales and guarantee to the process managers the stability of the support and its presence on the market over several decades. However it is realistic to expect that SMC will attract widespread use within a decade in a variety of applications, from chromatography to bioconversions, solid phase extractions and solid phase synthesis. 

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