Carbon quantum dots-modified ferrofluid for dispersive solid-phase extraction of phenolic compounds in water and milk samples

In this study, novel carbon quantum dots/oleic acid-coated Fe3O4 composites (Fe3O4-OA/CQDs) were successfully synthesized via a simple synthesis strategy and used to prepare the ferrofluid for the extraction and determination of phenolic compounds from water and pretreated milk samples followed by HPLC. The ferrofluid was composed of ionic liquids (ILs) and Fe3O4-OA/CQDs. With the introduction of CQDs, the ferrofluid showed good dispersing capability in aqueous samples, and the method exhibited lower relative standard deviations (RSDs) (1.1-2.1%), which indicated its good reproducibility. In addition, a proper carbon chain length for ILs might maintain the integrity of the ferrofluid during the extraction process and increase the extraction efficiency of the method. Under the optimum conditions, the limits of detection were in the range of 0.09-0.17 mu g L-1. And the intra-day and inter-day precision (RSD%) for the analytes at 20 and 100 mu g L-1 were in the range of 1.5-2.6% and 1.6-2.8%, respectively. The recoveries of bisphenols and 4-tert-octylphenol in water and milk samples were between 94.5 and 102.1%, and the RSDs were all in range of 1.7 to 4.1%. (C) 2018 Elsevier B.V. All rights reserved.