Polydopamine-functionalized magnetic iron oxide for the determination of trace levels of lead in bovine milk.

In this work, a novel sorbent based on polydopamine-functionalized magnetic ferric oxide (Fe3 O4 ) was synthesized and applied for dispersive solid phase extraction of Pb(II) in bovine milk samples. The extracts were analyzed by flame atomic absorption spectrometry (FAAS). The sorbent was characterized with different analytical techniques (XRD, FT-IR, SEM, TEM, VSM and EDX). To reach the maximum extraction efficiency of Pb(II), some effective parameters on both adsorption and desorption steps were optimized with the aid of central composite design and response surface methodology. Under the optimal conditions, the method provided an enhancement factor of 40.5 corresponding to the absolute recovery of 81%. LOD and LOQ were found as 0.13 and 0.43 ng mL-1 , respectively. The calibration curve was linear over the concentration range of 3.0-300 ng mL-1  (R2  = 0.9957). The intra and inter-day precisions (RSD%) of the method were calculated as 3.2% and 5.6%, respectively. Finally, the method was successfully applied for the determination of Pb(II) in different bovine milk samples. The Pb(II) content in one of the investigated milk samples was found to exceed the maximum permissible limit (20 μg L-1 ) set by Codex Alimentarius Commission. The relative recoveries were obtained within the range of 86.5-93.6.