A novel evaluation method for extrapolated retention factor in determination of n-octanol/water partition coefficient of halogenated organic pollutants by reversed-phase high performance liquid chromatography

The retention factor corresponding to pure water in reversed-phase high performance liquid chromatography (RP-HPLC), kw, was commonly obtained by extrapolation of retention factor (k) in a mixture of organic modifier and water as mobile phase in tedious experiments. In this paper, a relationship between log kw and log k for directly determining kw has been proposed for the first time. With a satisfactory validation, the approach was confirmed to enable easy and accurate evaluation of kw for compounds in question with similar structure to model compounds. Eight PCB congeners with different degree of chlorination were selected as a training set for modeling the log kw − log k correlation on both silica-based C8 and C18 stationary phases to evaluate log kw of sample compounds including seven PCB, six PBB and eight PBDE congeners. These eight model PCBs were subsequently combined with seven structure-similar benzene derivatives possessing reliable experimental Kow values as a whole training set for log Kow − log kw regressions on the two stationary phases. Consequently, the evaluated log kw values of sample compounds were used to determine their log Kow by the derived log Kow − log kw models. The log Kow values obtained by these evaluated log kw were well comparable with those obtained by experimental-extrapolated log kw, demonstrating that the proposed method for log kw evaluation in this present study could be an effective means in lipophilicity study of environmental contaminants with numerous congeners. As a result, log Kow data of many PCBs, PBBs and PBDEs could be offered. These contaminants are considered to widely exist in the environment, but there have been no reliable experimental Kow data available yet.

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► A novel log kw evaluation protocol was proposed for the first time.
► The approach greatly simplified Kow measuring procedure for lipophilic compounds.
► Log Kow data of 21 PCBs, PBBs and PBDEs were determined for the first time.