Determination of partition coefficients of chlorinated phenols,guaiacols and catechols by shake-flask GC and HPLC

The logarithm of the partition coefficients in the n-octanol-water system, log P, of 21 chlorinated phenols, guaiacols and catechols are determined, by both shake-flask gas chromatography (GC) and high pressure liquid chromatography (HPLC). In the shake-flask GC method, the water phase, after equilibration with spiked octanol, was analysed by glass capillary GC with electron capture detection. The relative responses of individual phenols were compared with those from before partition, and the partition coefficients were calculated. In the HPLC method, the capacity factors were used for calculating the log P values by calibration using four chlorophenols with known log P values. The use of short columns with 3 μm packing materials, combined with amperometric detection, offers fast and sensitive determinations.The results from both these methods have high precision, and agree well with the values calculated according to Hansch (1). The small deviations between the results obtained by shake-flask GC and HPLC for the compounds which have high dipole moments can be explained by the influence of different dipole moments and hydrogen bonding affinities in the solute-solvent and solute-stationary phase interactions. Compared with these interactions, the salt effect for concentrations lower than 1 M sodium chloride is negligible.