Core–shell molecularly imprinted polymer-based solid-phase microextraction fiber for ultra trace analysis of endosulfan I and II in real aqueous matrix through gas chromatography–micro electron capture detector

In this study, core–shell molecularly imprinted polymer selective for endosulfan I and II was prepared by copolymerization of Fe3O4@SiO2-methacrylamide composites and N,N′-methylene-bis-acrylamide. The synthesized polymer was thoroughly characterized by FT-IR, TGA, and SEM. The adsorption properties of the MIP and NIP were demonstrated by equilibrium rebinding experiments, pseudo-second-order kinetic model, LF-isotherm and Scatchard analysis. The competitive recognition studies were performed with endosulfan I and II and structurally similar compounds: aldrin, dieldrin and heptachlor. The imprinting factors (IF) of endosulfan I and II were found to be 10.1 and 9.1, respectively, which were much higher than the imprinting factors (IF) of other cyclodienes. The imprinted polymer was then coated on stainless steel wire to develop an easy and simple laboratory made solid phase microextraction device for selective extraction of endosulfan I and II from water samples of environmental importance. Also the main parameters influencing coating of fiber and microextraction procedure were investigated and optimized using Plackett–Burman and Central Composite designs. The developed method was thoroughly validated for its linearity, selectivity, precision and accuracy. The developed MISPME methodʹs linearity ranged from 7 to 5 × 103 ng l−1 (R2 = 0.999) and from 10 to 5 × 103 ng l−1 (R2 = 0.999) for endosulfan I and II, respectively. The limits of detection for endosulfan I and II were found to be 2 ng l−1 and 3 ng l−1, respectively. However, the limits of quantification for endosulfan I and II were 7 ng l−1 and 10 ng l−1, respectively.