Chromatographic supports, scale

The limitations of standard reversed-phase materials have been partially overcome by introducing modem, specially deactivated hydrocarbon-silica pha.ses ]126]. the hydrocarbonaceous phases immobilized on alumina or zirconia support ]127] and the polymeric materials ]128]. Using the latter two types of stationary phase materials one can determine the HPLC capacity factors at acidic, neutral and alkaline conditions. This way a universal, continuous chromatographic hydrophobicity scale can be constructed like the standard log P scale ] 129]. 

The concept of theoretical plates in chromatography is described elsewhere, and is not repeated here (18,19). Pieri et al. have described the application of the theoretical plate concept to column scale-up and demonstrated its utility in scale-up of pheromone separation over silica gel (15). We have found this same approach to be useful in separations over ion exchange resins used as chromatographic supports. In essence, this approach gives an estimate of column length for a given separation if the particle size is changed. This is based on empirical correlation of the number of theoretical plates, JV, ... 

To avoid the possibility that a small peptide from a phage-displayed library will not bind adequately when immobilized on a solid support, Baumbach and Hammond suggested that combinatorial peptide libraries for protein purification be synthesized directly on resins that could be used as chromatographic supports on a large scaled, in this way, any ligand that is identified is already on a platform or format that would facilitate implementation in downstream processing. The one-bead-one-peptide solid phase library format is ideally suited for this purpose, if the library is built on chromatographic resins that can withstand the harsh solvent conditions used for peptide synthesis. 

For large-scale preparative separations, porous particles with larger diameters are used. Use of chromatographic supports with a larger particle size allows the use of higher flow rates at lower back pressure, especially at the early stages of protein or peptide purification. 

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