High performance liquid chromatographic determination of the enantiomers of beta-adrenoceptor blocking agents in biological fluids. I: Studies with pindolol.

This paper describes a high-performance liquid chromatographic procedure for the analysis of (+)- and (-)-pindolol in biological fluids. Racemic pindolol is extracted from alkalinized plasma or urine into ether, then purified by two steps of back extraction. The final extract is reacted with (S)-(-)-alpha-methylbenzyl isocyanate at room temperature, forming urea diastereoisomers as suggested by mass spectral analysis. Separation of the two diastereoisomers is accomplished by high-performance liquid chromatography with fluorescence detection. The assay is reproducible and precise for both (+)- and (-)-pindolol in human plasma and urine, as judged by a coefficient of variation of less than 10% at most concentrations. The standard curves for (+)- and (-)-pindolol in plasma are linear between 10-100 ng/mL, and between 100-2500 ng/mL in urine. The lower limit of detection is approximately 2 ng/mL for each enantiomer in plasma. This procedure can be readily adapted for the stereospecific assay of other beta-adrenoceptor blocking agents as demonstrated by the base-line separation of atenolol and acebutolol.