& A method termed pseudo-stir bar hollow fiber solid=liquid phase microextraction (HF-SLPME) was utilized to extract three b-blockers—atenolol, metoprolol, and propranolol—in environmental waters. The extracted b-blockers were then separated, identified, and quantified by highperformance liquid chromatography with fluorescence detection. In HF-SLPME a porous polypropylene hollow fiber filled with MWCNTs reinforced organic solvent that acts as an analyte trap to pre-concentrate b-blockers from water samples. Both ends of the hollow fiber segment are sealed with magnetic stoppers. This device is placed inside the aqueous feed solution and plays the rule of a pseudo-stir bar. The effective parameters are optimized. The extracted b-blockers were analyzed at room temperature by high-performance liquid chromatography-fluorescence detection. The results showed that practical pre-concentration factors varied from 25.2–822. Under the optimized extraction conditions, the method showed good linearity and low limits of detections, 15.0, 10.0, 1.0 lgL
1 for atenolol, metoprolol, and propranolol, respectively. Relative recovery of b-blockers in real water samples were between 89.7–93.1 for tap water, 88.9–90.7 for clinical waste water, and 91.2–93.8 for industrial waste water with RSDs between 0.7–1.4%.

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