Here, we report C18-LC retention factors measured for a vastly extended set of anionic PFAS including alternatives to PFOA or PFOS. Nonfluorinated compounds from three groups of alkyl surfactants (i.e., carboxylates, sulfonates, sulfates) are also tested for comparison. The use of a shorter C18 column than in past studies allows measurement at φMeOH < 0.5. Mathematical models are fitted to the k data to extrapolate or interpolate k values at φMeOH of 0 (k0), 0.25 (k25), and 0.5 (k50). k25 and k50 are also included because they can be interpolated more frequently and determined more accurately than k0. For all k values, 95% confidence intervals (CIs) are provided to account for uncertainty. These k values are compared to environmentally relevant partition coefficients available in the literature to evaluate their potential as hydrophobic sorption indicators.