Recently, de Voogt et al. proposed isocratic reversedphase liquid chromatography (LC) retention (or capacity) factors (k) measured with an octadecyl group bonded silica (C18) column as a hydrophobicity indicator for fluorinated and nonfluorinated anionic surfactants. They measured k at varying volume fractions of methanol (φMeOH) in the aqueous eluent and extrapolated k at 100 % water (k0) for each surfactant. Since k0 reflects the actual sorption behavior from water to an organic solid phase (i.e., C18 phase), it can serve as a useful hydrophobicity indicator. While there have been decades of research employing LC retention measurements to characterize hydrophobic partition properties, most studies have been aimed at estimating Kow values for LC retention. The use of an LC approach is particularly sensible for anionic compounds because an alternative to Kow is required for this group of compounds. While de Voogt et al. used perfluoroalkyl carboxylates (PFCAs) and sulfonates (PFSAs) with different alkyl chain lengths, the PFAS of current concern are more diverse and thus an extension of the data set may be warranted. In addition, they performed the LC retention measurement at relatively high MeOH concentrations, primarily at φMeOH ≥ 0.5, and extrapolated k0 over a long range, which could introduce substantial uncertainty in the derived k0 values.