Column liquid chromatographic determination of hydrolysed bopindolol, in the picogram per millilitre range in plasma, using cartridge extraction and dual electrochemical detection.

A highly sensitive and specific column liquid chromatographic assay with electrochemical detection was developed for hydrolysed bopindolol, an active metabolite of bopindolol (Sandonorm) in human plasma. The pre-chromatographic sample preparation involved Extrelut column clean-up followed by liquid extraction of the organic extract into dilute acetic acid. Separation was on a Nucleosil ODS 3-microns column at 40 degrees C, with a phosphate buffer-methanol mobile phase. Detection was performed at +450 mV with an ESA electrochemical detector. Mepindolol was used as internal standard and quantitation was based on peak-area ratios. Total analysis time was 14 min per sample. The recovery rate of the assay was at least 70% for both compounds. A detection limit as low as 25 pg/ml, starting with 1 ml of plasma, was achieved. The day-to-day reproducibility and accuracy, checked with quality-control samples, demonstrated the reliability of this assay used by different analysts, on different chromatographic systems and over a long period of time.