Solid-phase microextraction coupled with capillary electrophoresis for the determination of propranolol enantiomers in urine using a sol–gel derived calix[4]arene fiber

A new type of diglycidyloxy-calix[4]arene coated fiber made by sol–gel method was initially prepared for capillary electrophoresis (CE) sample pretreatment. By using headspace solid-phase microextraction (SPME) combined with a novel back-extraction facility coupled off-line to capillary zone electrophoresis (CZE), the simultaneous determination of propranolol enantiomers in human urine was achieved. The clean up effect and preconcentration effect were realized for the first time without derivatization during the SPME process in terms of these strong polarity and thermal stable compounds. Ultrasonic back-extraction and field amplified sample injection (FASI) technologies were employed. Extraction and back-extraction parameters were optimized. Preconcentration of the sample by calix[4]arene fiber based SPME and FASI increased the sensitivity, yielding a limit of detection (LOD) of 0.01 μg/ml by CZE–diode array detection (DAD). Method repeatability (RSD < 6.5%) and fiber reusability (>150 extraction procedures) were observed over a linear range (0.05–10 μg/ml) in urine samples. Based on the superior thermal stability, high alkali- and solvent-resistant ability, marvelous repeatability and long lifetime of the novel fiber, this SPME–FASI–CZE procedure could meet the demand of minimum required performance limit (MRPL) set by the World Anti-doping Agency (WADA) for the detection of propranolol in urine samples.