HPLC-based KOW estimation methods for polybrominated diphenyl ethers.

Description

Octanol-water partition coefficients (KOW) of selected polybrominated diphenyl ethers (PBDEs), polychlorinated naphthalenes (PCNs), and hexabromocyclododecane (HBCD) isomers are estimated using retention time measurements on reversed-phase HPLC columns. Three methods are evaluated in terms of experimental simplicity and speed, and accuracy of K OW estimation, using chlorobenzenes (CBzs) and polychlorinated biphenyls (PCBs) as reference compounds. All three methods are found to be affected by structural differences between the calibration compounds. Differences in elution are found to be related to the planarity of the compounds. Simple isocratic measurements are shown to be insufficient for accurately estimating the KOW of hydrophobic compounds. Both a gradient elution method and a method based on a calibration using temperature-dependent KOW values of CBzs are able to estimate K OW values for these compounds with good accuracy. Log KOW values of 5.07--8.12 are reported from the gradient method, and 5.54 to 7.18 from the temperature-dependent method for mono- to hexa-brominated PBDEs, which agree well with recently published log KOW values measured directly by slow-stirring.

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