Sol–gel coated polydimethylsiloxane/β-cyclodextrin as novel stationary phase for stir bar sorptive extraction and its application to analysis of estrogens and bisphenol A

A sol–gel technique was used for the preparation of a stir bar coated with a composite composed of polydimethysiloxane and β-cyclodextrin (PDMS/β-CD). The sol–gel mechanism during coating procedure was discussed and successful binding of β-CD to the sol–gel network was confirmed by the IR spectra. Scanning electron micrographs of the stir bars revealed a homogeneous surface with a film thickness of 30–150 μm attributing to different coating times. Good thermal stability and solvent-resistance of the stir bar were found thanks to chemical binding formed between the stationary phase and the glass substrate. The PDMS/β-CD coated stir bar was proved to have better selectivity to polar compounds compared to the PDMS coated stir bar, and higher extraction capacity compared to the corresponding PDMS/β-CD coated fiber. Methods for the determinations of estrogens in environmental water, bisphenol A in drinking water and in leachate of one-off dishware by the PDMS/β-CD coated stir bar coupled with high-performance liquid chromatography (HPLC) were developed. The limits of detection were within the range of 0.04–0.11 μg l−1 for estrogens using UV detection and 8 ng l−1 for bisphenol A using fluorescence detection. Reproducibility with RSD less than 9.7% for extractions of real water samples at μg l−1 or ng l−1 level was obtained.