Selective extraction of β-blockers from biological fluids by column-switching high-performance liquid chromatography using an internal-surface phenylboronic acid precolumn

Abstract A column-switching HPLC method using an internal-surface phenylboronic acid precolumn for the selective extraction of β-blockers from biological fluids has been developed. Filtered urine and plasma samples (50 μl) were injected onto the precolumn equilibrated with methanol-0.05 M disodium hydrogenphosphate (5:95, v/v). After the precolumn had been washed breifly, the selectively retained β-blockers were eluted with methol-0.05 M phosphate buffer (pH 2.0) and transferred to a reversed-phase analytical column, on which they were then separated. Even after exposure to at least 160 injections of non-treated urine and plasma samples, the retention efficiency of the precolumn was maintained with no increase in back pressure. Quantitative recoveries and good reproducibility were demonstrated with pindolol.