Rapid separation and sensitive detection method for β-blockers by pressure-assisted capillary electrochromatography–electrospray ionization mass spectrometry

A new method for rapid separation and sensitive detection of β-blockers by pressure-assisted capillary electrochromatography (pCEC) with electrospray ionization mass spectrometry (ESI-MS) using silica-based monolithic column was studied in this paper. The proposed method has been confirmed to be very powerful since the fast mass transfer property and good permeability of silica monolithic column was used in this pCEC–ESI-MS system. In this work, a silica monolithic column was prepared with sol–gel method for simultaneous fast separation of β-blockers. Furthermore, in order to obtain the highly selective and sensitive result of pCEC–ESI-MS, both the CEC separation and MS detection parameters were optimized in detail. Under the optimized conditions, namely 80% acetonitrile and 20% 20 mmol/L ammonium acetate (pH 6.0) as the mobile phase, 20 kV and 8 bar as the separation voltage and the assisted pressure, isopropanol/water (1:1, v/v) containing 7.5 mmol/L acetic acid as the sheath liquid, and 3 μL/min as the flow rate of sheath liquid, seven β-blockers were well separated within 11 min with detection limits in the range of 0.15–0.80 ng/mL (defined as S/N = 3). The recoveries of spiked urine samples of these β-blockers were between 86.3 and 103% with the RSDs lower than 8.0%. The real samples from some male volunteers were successfully analyzed and confirmed with the proposed method. Comparing with GC–MS or LC–MS, the new method has some superiority (such as fast analysis capacity and simple pretreatment) in clinical practice and doping control.