High Performance Liquid Chromatography – HPLC

High Pressure – HPLC Adsorbents

It is known that HPLC, Column Chromatography and TLC techniques are governed by the same basic laws. The separation is influenced by the quality of the sorbent, the physical elution parameters and the solvent system. Therefore, it is theoretically simple to change from one technique to the other. Practically, however, it is a very complex matter. This complexity is even amplified if the sorbents used differ in their separation behavior.

SAI developed HPLC adsorbents that can be used with any liquid chromatograph. They have extremely narrow particle size ranges and optimum permeability when packed in columns. The HPLC procedure avoids shortcomings of the conventional gravity column, such as excessive interstitial volumes of "large" dimensions. Due to the short time of residence of the sample on the column, a considerable reduction of peak broadening is obtained as optimum elution flow conditions at minimum time of diffusion are exercised. The separation efficiency of this technique is at least equivalent to that of gas chromatography. Compounds composed of large molecules and those that are prone to cracking when exposed to elevated temperature survive an HP liquid chromatography. The latter pertains to almost 85 percent of all known organic compounds as they are high boiling and of high molecular weight.

SAI developed two series of high resolution products: Silicas and Aluminas.

HPLC Silica

SAI 60 Angstrom Silicas are irregularly shaped particles of porous, rigid structure. Their particle range is very closely controlled and by this virtue they neither contain too many fines that clog the columns nor too many coarse particles that impair the separation. Back pressure of the column is kept relatively low and still a high number of theoretical plates per length can be obtained. Closely controlled narrow cuts of this kind also facilitate the uniform packing of the columns.

Clean sieve cuts are essential for HPLC sorbents. SAI sorbents guarantee 90% plus to be within the limits indicated on the label. Not every sorbent in the market meets this high quality. The particle distribution of a high quality 32-100 micron silica is shown on the graph.

SAI’s complete range of silicas, from 3-500 microns, facilitates a scaling up from the micro-analytical to the preparative scale. The same is true when analytical procedures must be scaled down in order to monitor pilot plant runs.

1 = good cut between 32 and 100 microns
2 = bad cut
3 = theoretical curve of a "monodispersed phase" at 63 microns

Sorbent Selection
The following SAI Silica Gel Sorbent Catalog #s are recommended: