apHera High pH

Reversed-Phase Columns
Amino Columns
Ordering Information
Product Literature

In recent years reversed phase chromatography has become predominant throughout high performance liquid chromatography applications. Column packings have generally been alkyl-bonded silica gels such as ODS, and, to a lesser extent, polystyrene-based porous gels. Silica based phases are mechanically stable and generally high in NTP. However, they cannot be used under alkaline conditions and their residual silanol groups tend to adsorb organic bases.

Conventional polystyrene gels are free from residual silanol groups and can be used under alkaline conditions but they are also low in NTP and undergo excessive shrinkage and swelling with various solvents, thus limiting the range of eluents that can be used. Polymer based reversed phase columns have, therefore, generally been viewed as inferior in strength and separation efficiency.

apHera™ reversed phase columns were developed specifically to provide the superior advantages of both silica and polystyrene columns, without the disadvantages of either. This was accomplished using a vinyl alcohol copolymer base that keeps the surface wetted even with high carbon loads. The columns are packed with butyl (C4), octyl (C8) or octadecyl (C18) packings obtained by the introduction of the alkyl function on the hydroxyl groups of vinyl alcohol copolymers. The porous structure has an average pore diameter large enough to produce ideal results for small analytes, peptides and small proteins. These columns equal silica based columns in separation efficiency with organic solvents but provide efficiency with buffered and alkaline solutions not possible on silica. Shrinkage and swelling are minimal in a broad range of solvents, and the high NTP values of these columns are practically unaffected by differing solvent polarities, unlike polystyrene based polymer columns. One of the most significant features is the logical elution order of alkylated bases where retention increases proportionately with increasing chain length.

The apHera columns represent a fundamental advance in liquid chromatography with a greatly expanded field of reversed phase applications.

Ordering Information

apHera amino columns are based on covalently bonded polyamine specifically optimized for the separation of mono- and oligosaccharides. The elution order mono-, di-, tri-saccharide shows increased elution volume with increased acetonitrile concentration and complete stability fo both acidic and alkaline eluates. The small, robust PVA copolymer bead provides mechanical and chemical strength as well as high column efficiency. Conventional amino columns based on silica do not show long column life, perhaps due to hydrolysis of the silica particle by the basic amino group. Since apHera uses a strong alkaline compatible polymer, these problems are eliminated. Stable retention time and long columns life are also characteristic of the column.