Ultrasound assisted dispersive SDS-coated amino-functionalized magnetic iron oxide nanoparticles for the efficient removal and recovery of phthalate esters from drinking and environmental water samples

The research presented in this paper investigates the removal of four phthalate esters named dimethyl phthalate (DMP), diethyl phthalate (DEP), butylbenzyl phthalate (BBP) and dibutyl phthalate (DBP) by ultrasound assisted dispersive magnetic solid phase extraction (UADM-SPE) and their determination using high performance liquid chromatography. In recent years, magnetic nanoparticles (MNP) have been appearing as a new type of important functional SPE materials, but they are very sensitive to oxidation and agglomerations; hence, their surface were coated with several organic [1] and inorganic [2] materials; which not only cause to protection of magnetic nanoparticles, but also provide a component substrate at the surface of nanoparticles for adsorption of analytes. SDS-coated amino-functionalized magnetic iron oxide nanoparticles were applied as an efficient adsorbent for both removal and pre-concentration of these phthalate esters. The surface modification of synthesized surface modified magnetic nanoparticles was made by self-assembly of SDS as micelle around amino-functionalized magnetic iron oxide nanoparticles in an acidic medium and these particles act like a magnetic core micelles. This method (UADM-SPE) consists of two main steps: firstly, phthalate esters are absorbed through a series of interactions on the surface of SDS-coated amino-functionalized magnetic iron oxide nanoparticles (removal step) and in the second step, the recovery of adsorbed analytes will be performed by desorption of them into a suitable solvent (desorption step). Response surface methodology based on doehlert design, as a multivariate statistic technique, was applied to optimize the level of effective parameters for improving the removal efficiency. Type and volume of desorption solvent were optimized separately. Under the optimum condition (pH=6.5, the ratio of SDS/MNP=2, extraction time=1 min, and desorbing solvent=200 ml of methanol), extraction recoveries for 100 ng/ml of phthalate esters were in the range of 67-97% with pre-concentration factors in the range of 134-180. Replicating the experiment in above condition for five times, gave the relative standard deviations lower than 8%. The calibration curves showed high linearity (R2=0.99) in the range of 0.1-800 ng/ml and the limit of detections were in the range of 0.08-0.15 ng/ml. The proposed method was successfully applied for both removal and trace determination of these four phthalate esters in drinking and environmental water samples.