column and shows a pattern similar to other nonpolar compounds on this wide-pore C3 column. The retention factor at high water contents shows a tailing off, which may indicate a lack of sorption capacity on this lower surface area/lower carbon content column. Figure shows the fit for N-butylaniline on the Bonus RP column. For this compound/column pair, the organic phase composition ranges from 2 -70 % organic, and shows that for this broad range of organic composition, the fit is not very good. While we could eliminate the outliers at the extremes of the organic composition range by visual inspection, that would be a very subjective process, so we elected to narrow the organic range of the fitted data by step-wise elimination of the extrema points, depending on the magnitude of the residuals in the corresponding retention factors. We elected to