SOLID-PHASE EXTRACTION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF AMITRIPTYLINE AND NORTRIPTYLINE IN HUMAN PLASMA

A simple, rapid cost-efficient solid-phase extraction and high perform ance liquid chromatographic method for the determination of amitriptyl ine and nortriptyline in human plasma is described. After conditioning of solid-phase sorbent diluted plasma samples were passed through the cartridge. Potentially interfering substances were washed, followed b y elution of amitriptyline, nortriptyline and maprotiline (internal st andard) from the sorbent. Eluates were collected, evaporated, reconsti tuted and injected directly and monitored at 215 mm Samples were chrom atographed on a 5 mu m Supelcosil LC-PCN (150 x 4.6 mm) using 0.01 M d ipotassium hydrogenphosphate (pH adjusted to 7 with 85% ortophosphoric acid)/acetonitrile/methanol (15:60:25, v/v) as the mobile phase. Reco veries for amitriptyline and nortriptyline were 96% and 85%, respectiv ely. The limit of detection and quantification for amitriptyline and n ortriptyline were 1 ng/mL and 5 ng/mL, respectively. The calibration c urves for amitriptyline and nortriptyline in human plasma were linear over the range 5-500 ng/mL. The method was applied in single dose (75 mg) clinical pharmacokinetic studies of amitriptyline in depressed pat ients.