The types of nonfluorinated structure also have a significant influence on the values of log k0. The log k0 values are in the order X:2 FTS > X:3 FTCA > X:2 FTCA > PFSA > PFCA when compounds with the same nCF2 are compared. Specifically, log k0 of X:2 FTS is 1.29±0.23 greater, X:3 FTCA is 0.91±0.02 greater, X:2 FTCA is 0.56±0.34 greater, and PFSA is 0.45±0.01 greater than that of PFCA at the same nCF2. The fluorotelomer substances have nonfluorinated carbon atoms, which make log k0 greater than perfluoroalkyl compounds with the same nCF2. Sulfonates appear to be more retained by the C18 column than carboxylates with the same number of (perfluoro)carbon atoms. Log k0 values of perfluoroalkyl ether acids are also greater than those of PFCAs with the same nCF2 but the difference varies widely (by 0.75±0.45 for PFECAs, 1.36±0.76 for PFESAs), reflecting the variable structure of ether-containing PFAS.