Ionic liquid coated copper wires and tubes for fiber-in-tube solid-phase microextraction

• Ionic liquids coated copper wires and tube were developed as a SPME device.
• Online SPME-HPLC analysis system was built by coupling the SPME device to HPLC.
• The SPME device provides good extraction efficiency for estrogens.
• Online analysis method is efficient to detect five estrogens analytes in water samples.

A fiber-in-tube solid-phase microextraction (SPME) device was developed by filling eleven copper wires into a copper tube, and all of those were functionalized with ionic liquids. Its morphology and surface properties were characterized by scanning electron microscopy. It was connected into high performance liquid chromatography (HPLC) equipment by replacing the sample loop of six-port injection valve, building the online SPME-HPLC system. In the optimization of extraction conditions, sampling rate, sample volume, pH of sample and desorption time were investigated with five estrogens as model analytes. Under the optimum conditions, an online SPME-HPLC analysis method was achieved, showing enrichment efficiency from 611 to 1661 and a good linearity of 0.06–60 μg L−1 with low detection limits of 0.02–0.05 μg L−1. It was applied to detect estrogens analytes in two water samples, with recoveries in the range of 85–114%. Relative standard deviation (n = 3) of extraction repeatability is in the range of 1.9–3.0%. Relative standard deviation of extraction tubes (n = 3) is in the range of 12–19%. The extraction mechanism is probably related to hydrophobic, π-π and dipole-dipole interactions between ionic liquids coating and estrogens analytes.