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Original Articles

AN IMPROVED ASSAY BY HPLC WITH AMPEROMETRIC DETECTION FOR THE DETERMINATION OF PHENTOLAMINE IN PLASMA

, , &
Pages 557-564 | Received 28 Jun 1999, Accepted 20 Jul 1999, Published online: 06 Feb 2007
 

Abstract

An improved method for the determination of phentolamine in human plasma samples was developed. After being alkalinized, plasma samples (1 mL) were extracted with diethyl ether and then back-extracted with O.1 N HCl. Analyses were carried out on a Novapak C8 column eluted with a mixture of sodium monochloroacetate (pH 3) and acetonitrile (75:25). Amperometric detection was performed by oxidation at 1000 mV, using a glassy carbon electrode against Ag/AgCl. Calibration curves, constructed over a 1 to 30 ng/mL plasma concentration range, were linear (r=0.999). Intra-assay coefficients of variation and accuracy for the determined concentrations were comprised within 7.6–10.9% and 94.0–105.6%, respectively. Inter-assay coefficient of variation and accuracy ranges were 10.4–20.7% and 93.2–102.7%, respectively. The method's detection limit was 0.2 ng/mL, allowing determination of oral phentolamine pharmacokinetics after administration of a 40 mg dose.

It is concluded that the present procedure is suitable for pharmacokinetic and bioavailability studies of oral phentolamine formulations presently used in the treatment of erectile dysfunction.

ACKNOWLEDGMENT

The authors are indebted to Mr. A. Franco for excellent photographic material.

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