Polar silanes and their use on silica supports

#The present invention relates to new stationary phases and their use in HPLC (High Performance Liquid Chromatography), LC/MS and other preparative and analytical methods. More particularly, this invention relates to new silanes, their immobilization on silica supports and use of the modified silica supports as stationary phases in liquid chromatography (LC), LC/MS and other preparative and analytical methods.

#HPLC is widely used to separate analytes in liquid samples. The sample is injected in an eluent into a chromatography column. The sample components are separated by one or more mechanisms including sorption, size exclusion, ion exchange or other interactions with the chromatography packing. The sample components are then detected by any conventional detector, e.g., UV, fluorescence or conductivity.

#Silica-based RP (reverse phase) packing materials are commonly used in chromatography columns. They contain unreacted silanol groups on the silica surfaces. Residual silanol sites can interact with polar analytes, especially with basic compounds via ion exchange, hydrogen bonding and dipole-dipole mechanisms. These interactions can create problems ranging from increased retention to excessive tailing and irreversible adsorption of the sample. These undesirable effects can be minimized by using ultra pure silica and maximizing the surface coverage with hydrophobic ligands and endcapping reagents. However, highly aqueous mobile phases are often required to conduct separation of hydrophilic analytes by RP HPLC. Conventional RP C18 columns show a reversible loss of retention when operated under these conditions. The rate and degree of retention loss can vary greatly among different columns. A common explanation for this effect is that the hydrophobic alkyl chains are not wettable and appear to fold down on the silica surface to avoid the exposure to hydrophilic media. In this folded or matted-down state, the alkyl chains have reduced surface area for hydrophobic interaction with the solutes resulting in loss of retention. Reid, T. S.; Henry, R. A., American Laboratory 24-28 (July 1999).

#FIG. 1 shows the comparison of silanol activity using developed ethanolsulfonamide C16 column, conventional C18 and two commercial polar-embedded phases A and B. Developed ethanolsulfonamide C16 column exhibits superior efficiency and peak shape.

#FIG. 2 shows the results of the amitriptyline test using newly developed ethanolsulfonamide C16 and ethanolamide C18 phases. Both phases provide excellent peak shapes.

#FIG. 3 shows the results of the polarity test using newly developed ethanolsulfonamide C16 and ethanolamide C18 phases. Both phases show excellent peak shapes for acidic (phenol and p-butyl benzoic acid) and basic analytes (pyridine and N,N-dimethyl aniline).

#The present invention relates to modified silanes and their use in forming modified silica supports. The silica supports have polar phases bound to their surface and are suitable for use in chromatographic separations. In a preferred embodiment, such modified silica supports are useful in reverse phase (RP) chromatography such as described herein in more detail as is well known in the prior art.

#The specification will first describe the modified silica support having a polar phase according to the present invention. Then it will describe the polar phase and different methods for making the modified silica support, including methods for making the polar phase.

#The modified silica support has the following Formula 1: 4