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Table 2 Experimental log Kow/D values for 12 surfactant test compounds and 2 reference compounds

From: A comparison of log Kow (n-octanol–water partition coefficient) values for non-ionic, anionic, cationic and amphoteric surfactants determined using predictions and experimental methods

Details of the test and reference compounds and their test conditions Experimental log Kow/D values determined using HPLC, slow-stirring and solubility ratio methods Meang Standard deviation
Class # Abbreviation pH HPLC [3] HPLC [7] Slow-stirring [2]a Solubility ratio method (using different CMC methods)
Surface tension [11]a SPME [6]a Literature mean CMC values [6]a
Non-ionic 1 C8EO4 7 4.20 3.50 2.64 NDc NDc NDc 3.42 1.10
2 C12EO4 7 6.40 ND 4.33 NDc NDc NDc 5.37 1.46
3 C12EO8 7 6.50 5.31 3.96 3.19 3.29 3.28 4.55 1.73
Anionic 4 C12AS 7 NA NA 1.92 − 0.11 − 0.61 − 0.42 0.91 1.44
5 C12E4S 7 NA NA 1.47 2.29 2.45 2.04 1.88 0.580
6 C12 carboxylate 7 NA NA 3.15 (5.20) 1.60 (3.65) 2.51 (4.56) 1.13 (3.18) 2.38 1.10
6 C12 carboxylate 2 NA NA 4.47 (4.47) ND ND ND 4.47 NR
6 C12 carboxylate 9 NA NA 1.47 (5.52) ND ND ND 1.47 NR
Cationic 7 C12TMACd 7 NA NA 0.68 2.25 2.21 2.24 1.47 1.11
8 C16TMACd 7 NA NA 1.83 3.65 3.46 3.06 2.74 1.29
9 C18BACd 7 NA NA 1.32 3.03 4.99 3.07 2.18 1.21
Amphoteric 10 C12–16ADBd 7 NA NA 3.69 1.88 ND 1.61 2.79 1.28
11 C12AAPBd 7 NA NA 2.59 1.75 ND 1.94 2.17 0.594
12 C12DAOd 7 NA NA 0.71 NDc NDc NDc 0.71 NR
Reference (neutral) 13 ATR 7 2.60 ND 2.67e ND 3.07 3.12 2.64 0.049
Reference (ionised) 14 PCP 7 NA ND 2.90f (5.55) ND 1.05b (3.70) 0.81b (3.48) 2.90 NR
  1. NA not applicable, as the HPLC method is only applicable to non-ionic compounds, ND not determined, NR not relevant
  2. aLog Kow values in brackets are calculated values of the neutral form of the compound, corrected for ionisation using Eq. 2
  3. bLog Kow values of pentachlorophenol have been calculated using the literature water solubility value of pentachlorophenol
  4. cNot possible to determine solubility in n-octanol quantitatively, so no log Kow data presented
  5. dThese cationic surfactants are permanently ionised under the test conditions
  6. eLiterature log Kow value for atrazine is 2.61
  7. fLiterature log Kow values for pentachlorophenol are 5.05 (at pH 5.1) and 5.87 for ionised and corrected neutral forms respectively [38]. A further similar literature value of 5.12 has also been reported [39]
  8. gCalculated using only values fully generated in this study (HPLC, Slow-stirring and Solubility ratio (based on CMC values determined by the surface tension method only)