High-performance liquid chromatographic method for the simultaneous determination of low-molecular-mass oligomers of polyethylene glycol in aqueous skin extracts.

The isocratic, reversed-phase, high-performance liquid chromatographic (HPLC) method presented provides a simple and rapid analytical technique for the simultaneous determination of low-molecular-mass oligomers of polyethylene glycol (PEG) in aqueous polymer samples containing polar contaminants of biologic origin. In the present case, individual molecular mass species were quantitated in aqueous skin extracts arising from the investigation of PEG transport through mammalian skin. PEGs were isolated and purified by solid-phase extraction using large-pore kieselguhr (Extrelut QE) cartridges, which selectively retained polar contaminants from excised skin specimens. Sample recoveries were found to be dependent upon molecular mass, ranging from 18.28% to 86.10%, but were highly reproducible. The mean inter-sample error (n > or = 5) for the extraction of twenty-six molecular mass species of PEG was less than 3%. Satisfactory resolution of primary molecular mass components was accomplished using a base-deactivated, C8 column (Supelcosil LC-8-DB) and a mobile phase consisting of methanol and water. Corresponding run times for the complete separation of individual oligomers ranged from 8 to 30 min, while the limit of detection for a particular molecular mass species was approximately 5 micrograms/ml. The method was further employed to determine the weight-average (Mw) and number-average (Mn) molecular mass distributions and polydispersity for three commercial PEG blends, as well as to characterize the methylene chloride/water distribution coefficients for twenty-two molecular mass species ranging from 282 to 1206 Da.