PROPERTIES OF SOME C-18 STATIONARY PHASES FOR PREPARATIVE LIQUID-CHROMATOGRAPHY .2. COLUMN EFFICIENCY

Apparent column efficiencies were measured for 2,6-dimethylphenol, 3-phenyl-1-propanol, m-cresol and methyl benzoate on six columns packed with two commercial octadecyl silica, using methanol-water solutions as the mobile phase. The columns having the less dense packing are also the most efficient (the long-term stability problem conventionally associated with low packing-density columns has not been studied). The dependence of the column efficiency on the sample size is well accounted for by the Knox-Pyper model, using the isotherm data previously determined and the solution of the ideal model to account for the thermodynamic contribution to band broadening.