STEREOSELECTIVE ANALYSIS OF NADOLOL IN HUMAN PLASMA

A stereoselective method, involving a single liquid-liquid extraction step, was developed and validated for the analysis of nadolol in human plasma, The assay involved extraction of nadolol and desmethyl-nadolo l (as internal standard (IS)) from alkalinized plasma into dichloromet hane, The organic solvent was separated and evaporated under nitrogen at 40 degrees C, A chiral derivatization scheme with (R-(-)-napthyleth ylisocyanate (50 mu L of 0.1% solution in dichloromethane for 60 min) was employed to convert the enantiomers of nadolol into the correspond ing diastereomeric derivatives, The residue was reconstituted in the m obile phase and injected onto a C-18 column, The mobile phase was a mi xture of methanol:tetrahydrofuran:water 152:7:41 by vol) containing ab out 0.001% v/v of both phosphoric acid and tetramethylethylenediamine. Fluorimetric detection was performed at excitation 230 and emission 3 30 nm, The assay was specific for the enantiomers of nadolol and the l ower limit of quantitation was 2 ng/mL for each of the enantiomers, An alysis of quality control samples resulted in precision estimates of 7 % RSD for inter-assay and 10.1% RSD for intra-assay and the predicted concentrations deviated less than 9.4% of the nominal values for the f our enantiomers, The extraction recoveries of the individual enantiome r was about 70%, Stability of nadolol enantiomers were established for four freeze/thaw cycle periods and in the autosampler at 5 degrees C for at least 116 h.