Liquid chromatographic analysis of di(2-ethylhexyl) phthalate: application to pharmacokinetic studies in the mongrel dog.

A high-performance liquid chromatographic (HPLC) assay was developed for the determination of di(2-ethylhexyl) phthalate (DEHP) in serum or plasma. Plasma DEHP concentrations that were measured by HPLC in specimens obtained from hemodialysis patients were in good agreement with corresponding concentrations that were measured by gas chromatography with selected ion monitoring (GC-SIM) (r2 = 0.996). Plasma DEHP concentrations were measured after intravenous DEHP administration (1.2-4.4 mg DEHP/kg body weight) to determine the effect of bilateral ureteral ligation on DEHP elimination in the mongrel dog. DEHP plasma clearance (approximately 6.3 ml/min/kg), steady-state distribution volume (approximately 0.21/kg), and terminal half-life (approximately 50 min) were unchanged in two dogs following bilateral ureteral ligation. DEHP terminal half-life and steady-state distribution volume were substantially smaller (25- to 70-fold) than reported previously in the rat or dog.

Reversed-phase liquid chromatography and gas chromatography/mass fragmentography compared for determination of tricyclic antidepressant drugs.

We compare measurement of the tricyclic antidepressants desipramine, imipramine, nortryptaline, and amitryptaline by reversed-phase "high-performance" liquid chromatography and by gas chromatography/mass fragmentography. The liquid-chromatographic procedure does not require ion-pairing reagents, and involves detection at 215 nm. The within-day and between-day CVs for this method were less than 5% and less than 7%, respectively, and linear-regression analysis of peak height vs concentration for each of the drugs showed excellent correlation (r greater than 0.97) over the range 0-250 microgram/L. Potential interferences with the internal standard (N-desmethyldoxepin) and nortryptaline were oxazepam and N-desmethyldiazepam, respectively, as shown by mass spectrometry. The interference could be circumvented by increasing the column temperature to 50 degrees C. We conclude that reversed-phase liquid chromatography with detection in the far-ultraviolet wavelengths provides an alternative to gas-chromatographic procedures for the tricyclic antidepressants, provided the analyst has prior knowledge of the patient's other medications.