Quantification of Pentazocine in Human Plasma by HPLC with Electrochemical Detection

Resolution and quantitation of pentazocine enantiomers in human serum by reversed-phase high-performance liquid chromatography using sulfated beta-cyclodextrin as chiral mobile phase additive and solid-phase extraction

A sensitive and stereospecific HPLC method was developed for the analysis of (-)- and (+)-pentazocine in human serum. The assay involves the use of a phenyl solid-phase extraction column for serum sample clean-up prior to HPLC analysis. Chromatographic resolution of the pentazocine enantiomers was performed on a octadecylsilane column with sulfated-beta-cyclodextrin (S-beta-CD) as the chiral mobile phase additive. The composition of the mobile phase was aqueous 10 mM potassium dihydrogenphosphate buffer pH 5.8 (adjusted with phosphoric acid)-absolute ethanol (80:20, v/v) containing 10 mM S-beta-CD at a flow-rate of 0.7 ml/min. Recoveries of (-)- and (+)-pentazocine were in the range of 91-93%. Linear calibration curves were obtained in the 20-400 ng/ml range for each enantiomer in serum. The detection limit based on S/N=3 was 15 ng/ml for each pentazocine enantiomer in serum with UV detection at 220 nm. The limit of quantitation for each enantiomer was 20 ng/ml. Precision calculated as R.S.D. and accuracy calculated as error were in the range 0.9-7.0% and 1.2-6.2%, respectively, for the (-)-enantiomer and 0.8- 7.6% and 1.2-4.6%, respectively, for the (+)-enantiomer (n=3).

HPLC separation of pentazocine enantiomers in serum using an ovomucoid chiral stationary phase

A stereospecific HPLC method was developed for the analysis of (-) and (+) pentazocine in human serum. Each enantiomer and the internal standard nalophine were isolated from serum using a liquid-liquid extraction procedure. Recoveries of 99.05 +/- 5.37 and 97.42 +/- 2.78% were obtained for (-) and (+) pentazocine, respectively. Resolution of the enantiomers was obtained by using an ovomucoid chiral stationary phase with a mobile phase of methanol:acetonitrile: 10 mM phosphate buffer, pH 5.8 (20:5.3:74.7 v/v/v). A resolution (Rs) value of 1.80 was obtained for the pentazocine enantiomers. Linear calibration curves were obtained in the 10-100 ng/mL range for each enantiomer in serum. The detection limit based on a signal-to-noise ratio of 3 was 5 ng/mL for each enantiomer in serum using fluorescence detection with excitation at 275 nm and emission set at 335 nm. The lowest quantifiable level was found to be 10 ng for each enantiomer. Precision and accuracy of the method were in the 3.8-4.8% and 1.3-4.2% ranges, respectively.