VINYL MODIFICATION OF FUSED-SILICA SURFACES IN POLYSILOXANE-COATED 10-50 MU-M I D CAPILLARIES FOR OPEN-TUBULAR LIQUID-CHROMATOGRAPHY

Attempts were made to improve the stability of narrow-bore open-tubular columns for liquid chromatography. In addition, the LC selectivity shift for thin stationary phase films was examined. Three different pretreatment methods based on vinyl-containing reagents were tested in 50 mum I.D. fused-silica capillaries. The modified capillaries were coated with the stationary phase PS 255, a polydimethylvinylsiloxane, and cross-linked. The columns were evaluated according to selectivity in LC and also to the degree of immobilization and column inertness in GC. Deactivating the capillaries with polydimethylvinylsiloxane was the preferred method. It was not possible to confirm bonding between the deactivation layer and the cross-linked polysiloxane stationary phase film. The proposal that the selectivity shift, for thin stationary phase films in open-tubular LC, originated from influence of the fused-silica surface on the stationary phase configuration could be excluded. The polydimethylvinylsiloxane method was also used in narrow-bore (10 mum I.D.) columns. Preliminary LC studies with anthracene derivatives as model substances indicated that deactivation has no influence on the efficiency.