Observations on the Wetting of Reversed-phase HPLC Packings

Library Number:
T. Walter;P. Iraneta;M. Capparella
HPLC''97, Birmingham, June 22-27, 1997
Content Type:
Content Subtype:
Deuterium oxide; Sulfanilamide; Procainamide
SymmetryShield RP8 5 µm Steel 3.9 mm 150 mm SymmetryShield RP18 5 µm Steel 3.9 mm 150 mm Symmetry C18 5 µm Steel 3.9 mm 150 mm Symmetry C8 5 µm Steel 3.9 mm 150 mm
ABSTRACT: The behavior of reversed-phase HPLC packings is strongly dependent on the interaction of the mobile phase with the stationary phase. One important aspect of this interaction is wetting, or spreading of the mobile phase on the stationary phase surface. The penetration of the mobile phase into the pores of porous packings is strongly affected by the degree of wetting, as well as by the pressure difference across the interface, and the pore size distribution of the packing. Because most of the surface area of porous packings resides in the pores, the extent of penetration of mobile phase into the pores affects retention times. We have developed chromatographic protocols to observe the wetting of reversed-phase packings, and determined the extent of wetting using water/methanol mobile phases of varying water content. Results are presented for a range of C18- and C8 silica packings, showing the effects of different pore size distributions and bonded phase coverages. Results will also be presented for novel reversed-phase packings containing an internal polar group [prepared by bonding silica with 3-(chlorodimethylsilyl)propyl-N-octylcarbmate or -N-octadecylcarbamate], which are wetted even by completely aqueous mobile phases.

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