Zeolitic imidazolate framework-8 as sorbent of micro-solid-phase extraction to determine estrogens in environmental water samples

A novel micro-solid-phase extraction (μ-SPE) device coupled with ultra-high performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS) was established to determine five typical estrogens in aqueous samples. Zeolitic imidazolate framework-8 (ZIF-8) as sorbent was packed in polypropylene membrane to construct the μ-SPE device. Important extraction parameters including extraction time, extraction temperature, desorption solvent, desorption time and sample pH were carefully optimized to improve the extraction efficiency of the μ-SPE device. ZIF-8 sorbent showed an exceptional chemical stability and extraction efficiency for estrogens. In theory, the high extraction efficiencies may be due to the coordination bonding, intermolecular π–π interactions and hydrophobic interactions between ZIF-8 and the estrogens. Under the most favorable extraction conditions, for estrogens in aqueous samples, the proposed method provided low limits of detection (0.05–0.1 μg/L), wide linearity range (three orders), excellent correlation coefficients (0.959–0.999) and satisfactory measurement precision (4.9–9.2%). which can meet the demand of determining estrogens at the trace level. Finally, the proposed method was successfully applied to determine the estrogens in real sewage water samples.