Packing materials for HPLC

Commercial alumina packing materials for HPLC have lower column efficiency values and lower specific surface areas (typically 100-250 m g ) which leads to a lower sample capacity. Another disadvantage of alumina is that the highly active surface has a tendency to catalyse deterioration reactions, which is particularly important for molecules which undergo base-catalysed degradation, because of the basic nature of the alumina surface. 

Relatively few molecular separations have been studied from the utilitarian standpoint. One of these, the purification of fullerenes via 8 , is discussed on p. 170. In a reciprocal experiment the separation of 4 " , 6 , and 8 with a column using a chemically-bonded C o silica stationary phase has been re-ported. Chromatographic selectivity has been achieved for amino acid esters and alkali metal cations on silica-bonded calix[4]arene tetraesters, the structure of which has been explored by and Si-CP-MAS NMR. Silica-bonded calixarenes have also been used as packing materials for HPLC columns that are capable of separating disubstituted aromatics, peptides, and nucleosides. The HPLC separation of phenols using 6 ° as a constituent of the eluent has been described. ... 

Ikai, T., Yamamoto, C., Kamigaito, M., and Okamoto, Y. (2008) Immobilized-type chiral packing materials for HPLC based... 

Tanaka, N. An approach to high-performance packing materials for HPLC. Chromatography 1999, 20, 190-193. 

The most common packing material in HPLC columns (Figure 13.4, C) is a solid with an organic group attached to it. For instance, the solid may have a hydrocarbon chain containing 18 carbons attached to it, making it hydrophobic. This type of column is called a C18 column or a reverse-phase column. Columns can be made with varying polarities and functionalities and thus can be used to carry out a wide variety of separations. 

Variation of the mobile-phase pH is one of the most powerful tools in controlling the separation for ionizable analytes. The main drawback of silica-based HPLC packing materials is their narrow applicable pH range. The other limitations are surface activity (or polarity), which for specific applications (such as separation of proteins or biologically active compounds) could play a major role. All these factors are the driving force for the search in alternative base materials for HPLC packings. 

Table 4.2 Some alkylsilyl-modified silica column packing materials for use in SPE and HPLC...

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