Cloud Point Extraction Combined with Liquid Chromatography Coupled to Tandem Mass Spectrometry for the Determination of Verapamil in Urine

Based on cloud point extraction, a HPLC method was developed for the determination of verapamil in urine. Non-ionic surfactant Triton X-100, an environmentally friendly solvent, was used for the micelle-mediated extraction. Some parameters that influence the extraction, such as the concentration of Triton X-100, effect of pH, incubation time, equilibration temperature and centrifugation parameters, were studied and optimised. The method suggested for the HPLCtandem mass spectrometry determination of verapamil in urine after cloud point extraction was validated. The calibration curve was linear in the range of 0.2-50 ng/mL. The limits of detection (3 sigma) and quantification (10 sigma) were 0.06 and 0.2 ng/mL, respectively. The matrix effect (96.5%), recovery of the extraction procedure (96%) and overall process efficiency (92.6%) were also estimated. All data validation is consistent with international acceptance criteria and no significant matrix effect was observed. The results show that the sensitivity, metrological characteristics, ecological safety, simplicity and convenience of the suggested procedure exceed its analogues based on extraction using organic solvents.