Dispersive liquid-liquid microextraction of propranolol enantiomers from human plasma based on the solidification of a floating organic droplet.

A dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet was developed and validated for the extraction of propranolol enantiomers from human plasma. The studied enantiomers were extracted from diluted and alkalized plasma samples using 1-undecanol as the extracting solvent. HPLC-fluorescence detection analyses were carried out on a chiral column, using n-hexane-ethanol (80:20, v/v) plus 0.2% triethylamine as the mobile phase, at a flow rate of 0.8 ml/min. The significant factors in the microextraction procedure, including extracting and disperser solvents volume, solution pH and salt contents were optimized by using a central composite design and the response surface methodology. Under optimized conditions, the mean recoveries were approximately 14% with linear responses over the 0.5-100 ng/ml concentration range for both enantiomers. The LOQ was 0.5 ng/ml (S/N = 10). Intra-day (n = 5) and inter-day (n = 3) assay precision (1 and 50 ng/ml) showed RSD lower than 8 and 9.5% for studied enantiomers, respectively. Finally, the method was successfully used for the determination of propranolol enantiomers in plasma samples obtained after single drug administration of racemic propranolol tablet to three healthy volunteers. The plasmatic concentrations of (-)-(S)-PROP were higher than those of (+)-(R)-PROP in all times after oral administration of the racemic drug. The obtained results proved that the proposed method is a powerful technique for sample preparation, providing suitable recoveries, efficient cleanup, high selectivity and sensitivity and low consumption of organic solvent for determination of the studied enantiomers in plasma samples after oral administration of the racemic drug to volunteers.