Vortex-assisted liquid-liquid extraction combined with field-amplified sample injection and sweeping micellar electrokinetic chromatography for improved determination of β-blockers in human urine.

A new micellar electrokinetic chromatography (MEKC) method was developed and validated for the analysis of carvedilol and propranolol in human urine samples. In this study, vortex-assisted liquid-liquid extraction (VALLE) coupled with field-amplified sample injection and sweeping was employed for biological sample clean-up and sensitivity enhancement in MEKC. After VALLE, the urine samples were analyzed by MEKC. Tris-phosphate buffer (60mmolL(-1), pH 2.0) containing 40% (v/v) methanol was first filled into an uncoated fused-silica capillary (56cm, 50µm i.d.). The pretreated urine sample was loaded by electrokinetic injection (10kV, 250s). The stacking and separation were performed using Tris-phosphate buffer (30mmolL(-1), pH 3.0) containing 30% (v/v) methanol and 50mmolL(-1) sodium dodecyl sulfate (SDS) at -25kV. Detection was carried out at 195 and 214nm for carvedilol and propranolol, respectively. The suggested method is linear (r(2)≥0.997) over a dynamic range of 0.005-1µgmL(-1) in urine. The intra- and inter-day relative standard deviation and relative error values of the method were below 20%, which shows good precision and accuracy. Finally, this method was successfully applied to the analysis of real urine samples.