CHARACTERIZATION OF RETENTIVITY OF REVERSED PHASE LIQUID-CHROMATOGRAPHY COLUMNS

There are dozens of commercially available reversed phase columns, most marked as C-8 or C-18 materials, but with no useful way of classifying their retentivity. A useful way of ranking these columns in terms of column "strength" or retentivity is presented. The method utilizes a value for ln k'w, the estimated retention of a solute from a mobile phase of 100% water, and the slope of the plot of ln K' vs. E(T)(30), the solvent polarity. The method is validated with 26 solutes varying in ln k'w from about 2 to over 20, on 14 different reversed phase columns. In agreement with previous work, it is found that the phase volume ratio of the column is the most important parameter in determining retentivity. It is strongly suggested that manufacturers adopt a uniform method of calculating this value and that it be made available in advertising, rather than the uninterpretable "% carbon".