A new method for the analysis of β₂-agonists in human urine by pressure-assisted capillary electrochromatography coupled with electrospray ionization-mass spectrometry using a silica-based monolithic column

A new pressure-assisted capillary electrochromatography coupled with electrospray ionization-mass spectrometry method using a silica-based monolithic column as separation media was developed for the analysis of β₂-agonists in human urine. Experimental conditions including the mobile phase, separation voltage, assisted pressure, and sheath liquid were optimized for the analysis: mobile phase composed of 82% (v/v) ACN and 18% (v/v) 20 mmol/L ammonium acetate (pH 6.0); separation voltage 25 kV; assisted pressure 2 bar; and the sheath liquid consisting of 7.5 mmol/L acetic acid in isopropanol/water 50/50% (v/v) that was delivered at a flow rate of 3.0 μL/min. Six β₂-agonists were separated within 12.5 min with LODs (defined as S/N = 3) in the range of 0.25-2.0 ng/mL. The absolute LODs of the developed method for analyzing six β₂-agonists ranged from 5.75 to 46.0 fg. Method repeatability of run-to-run and column-to-column was satisfactory. The recovery obtained from the analysis of spiked urine samples was between 88.2% and 106% with RSDs lower than 6.68%. The method was successfully applied to the analysis of real urine sample from volunteers.