suitable for use as a stationary phase in zwitterionic high performance liquid chromatography may comprise porous silica particles the particles may comprise covalently bound zwitterionic groups methods for manufacturing and applying the silica particles exist application_number US 71093704 A description while the present invention has been described with specificity in accordance with certain of its preferred embodiments the following examples serve only to illustrate the invention and are not intended to limit the same if sources are not specifically described materials are known and commercially available reagents and chemicals used in the preparation of the invention were obtained as follows kromasil spherical silica particles 10 u03bcm particle size with 200 u00e5 pore size were obtained from eka chemicals bohus sweden the zwitterionic monomers 3 n n dimethyl n methacryloyloxyethyl ammonium propanesulfonate spe 3637 26 1 1 3 sulfopropyl 2 vinylpyridinium betaine spv were obtained from raschig chemie ludwigshafen germany while tert butyl hydroperoxide 5 m in octane was purchased from aldrich steinheim germany the zwitterionic amphiphile used for comparative u03b6 potential measurein combinawith nucleosil c 18 3 u03bcm 120 u00e5 macherey nagel d u00fcren germany was n don n dimethyl 3 ammonio 1 propanesulfonate sb12 aldrich thionyl chloride 99was obtained from fluka buchs switzerland and methanol hplc grade was from j t baker deventeer holland perchloric acid 70 p a was from riedel de ha u00ebn seelze germany acetone purum for washing was from svenda ab stockholm sweden and chloroform p a from prolabo fontenay s bois france water was purified by a milli q water purification system millipore bedford mass the salts sodium sulfate sodium chloride sodium bromide sodium tio cyanate sodium nitrate sodium iodide sodium perchlorate and ammonium acetate were.