Determination of plasticizers in aqueous samples using simultaneous homogeneous liquid–liquid and dispersive liquid–liquid microextraction and GC–MS

The alkyl or aryl esters of 1,2–benzenedicarboxylic acid commonly known as phthalate esters (PEs), and di–(2ethylhexyl) adipate (DEHA) are used as plasticizers in order to improve the flexibility of various polymers. Also, PEs and DEHA are used in several industrial sectors such as paints, cosmetics, glues, photographic films, insect repellents and etc [1]. Due to wide applications of these chemical compounds, the production amount of them is several million tons per year. The migration of PEs and DEHA from plasticized products into the environment and foods consumed by human due to not covalently bounded of these compounds to plastics can constitute a great menace to the environment and human health [2]. It was shown that PEs are estrogenic, carcinogenic, and have an endocrine disruption activity [3]. So, their determination in environmental matrices and human body has attracted great importance among the researchers. Now, mostly chromatographic techniques such as gas and high–performance liquid chromatography are used for analysis of PEs [4, 5]. But, due to trace concentrations of these compounds in real samples and in order to obtain the reliable results performing a sample preparation procedure before chromatographic techniques is essential. In the present work, a green mode of simultaneous homogeneous liquid–liquid microextraction and dispersive liquid–liquid microextraction assisted by sodium sulfate has been developed for the extraction and preconcentration of some phthalate esters and di–(2–ethylhexyl) adipate from different aqueous samples prior to their determination by gas chromatography–mass spectrometry. In this method, an appropriate mixture of sodium sulfate solution (phase separation agent and disperser solvent) containing iso–propanol (extraction solvent) is rapidly injected into an aqueous solution containing sodium sulfate and the selected analytes. By this action the extraction solvent is dispersed as fine droplets into the aqueous phase. After centrifuging the extractant containing the extracted analytes is collected on the surface of the aqueous phase. Under the optimum conditions, limits of detection and quantification were obtained in the ranges of 14–33, and 47–110 ng L–1, respectively. The extraction recoveries and enrichment factors of the selected phthalate esters ranged from 79–94% and 395–470, respectively. The relative standard deviations were ≤ 7% for intra– (n=6) and inter–day (n=4) precisions at a concentration of 250 ng L–1 of each analyte.