The distribution constants (K-D,K-SF CO2) of 2-methyl-5-hexyloxymethyl-8-quinolinol (HMO(6)Q) between supercritical (SF) CO2 and water were determined at I = 0,1 M (H,Na)NO3 (1 M = 1 mol dm(-3)), 45 degrees C and 8.6 - 20.4 MPa. The log K-D,K- SF CO2 values at 8.6, 12.2, 15.7, and 20.4 MPa were 1.18 +/- 0.13, 1.76 +/- 0.14, 2.18 +/- 0.17, and 3.02 +/- 0.21, respectively. The K-D,K-SF CO2 value at 20.4 MPa was about one tenth of that (log K-D = 4.08 +/- 0.02) for the heptane-water system at 45 degrees C and an atmosphere.