INVESTIGATION OF CROSS-LINKING CHIRAL STATIONARY PHASES WITHIN CAPILLARY COLUMNS

Four diamide chiral stationary phases (CSPs), undecenoyl-L-valine-(S)-alpha-phenylethylamide (CSP-1), OV-225-L-valine-tert.-butylamide (CSP-2), XE-60-L-valine-tert.-butylamide (CSP-3) and polycyanoethyl vinyl siloxane 25% cyanoethyl-L-valine-tert.-butylamide, were cross-linked within both glass and fused-silica capillary columns with dibenzoyl peroxide (DBP) as the cross-linking reagent. The effects of the CSP skeleton on the degree of cross-linking and racemization (decrease in enantiomeric excess) of the stationary phase during cross-linking were investigated. The performance of the cross-linked columns in terms of enantioselectivity, thermal stability, acid-base characteristics and column efficiency were determined and compared. The results show that the CSP skeleton may have considerable effects on both cross-linking and racemization.