The influence of solvent structure on the reordering-resolvation of alkyl modified silica

The current work examines the reordering-resolvation of octyl modified sili ca in contact with binary hydro-organic solvents at near aqueous conditions . As such, it is as an extension of a number of previous investigations, th at has been concerned with the influence of various stationary phase parame ters on the reordering-resolvation of alkyl and alkylamide bonded phases un der totally aqueous eluent conditions. The organic modifiers used are two s tructure-making solvents, methanol and acetonitrile, and two structure-brea king solvents, 1,4-dioxane and dimethyl sulfoxide. These two classes of sol vents have either a positive or a negative influence on the temperature, T- 0, where reordering-resolvation occurs relative to water. Likewise, plots o f T-0 vs. mole% of the organic modifier are linear within the concentration range where the two classes of solvents behave as either structure-making or structure-breaking agents. (C) 2000 John Wiley & Sons, Inc.