Sweeping-micellar electrokinetic chromatography for the simultaneous analysis of tricyclic antidepressant and β-blocker drugs in wastewater

The simultaneous analysis of tricyclic antidepressant (amitriptyline, clomipramine, doxepin and nortriptyline) and ß-blocker (alprenolol, labetalol and propranolol) drugs in wastewater was developed via sweeping–micellar electrokinetic chromatography (MEKC) together with a simple liquid–liquid extraction step. For sweeping–MEKC, the amount of organic modifier in the separation electrolyte, the concentration of phosphoric acid in the sample matrix and the injection time of the sample were optimized. Sensitivity enhancements of up to 305-fold were achieved via sweeping. This allowed limits of detection (LOD) from 7 to 27 ng/mL. The relative standard deviations of migration time, corrected peak area and peak height were less than 3.2%, 7.8% and 4.5%, respectively. Liquid–liquid extraction using dichloromethane as solvent afforded up to 21-fold enrichment of the drugs from spiked wastewater. No interference of the sample matrix was observed and recoveries were obtained in the range of 77–113% for all analytes except labetalol at three spiking levels of 16, 80 and 160 ng/mL. Detection at the ng/mL level makes this simple, environmentally friendly and cost effective method competitive against recently reported methods using advanced liquid-phase separation techniques for monitoring similar drugs in wastewater.