SOLID-PHASE EXTRACTION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF DOBUTAMINE IN PLASMA OF DIALYZED PATIENTS

An isocratic reversed-phase high performance liquid chromatographic me thod has been developed for the determination of dobutamine in the pla sma of dialysed patients. A solid phase extraction method with a Sep-P ak C-18 cartridge was used to isolate the drug and isoxsuprine (intern al standard) from plasma. The separation was carried out on an ODS-Hyp ersil column with 0.1 M phosphate buffer: acetonitrile: methanol (72:2 0:8 v/v/v) as the mobile phase. The recovery of dobutamine added to pl asma by the extraction procedure was 87+/-2.3% (mean+/-SD). The accura cy and reproducibility of the method were within acceptable limits ove r the concentration range 0-1000 ng/mL. Quantification was by fluoresc ence detection at 275 nm excitation and 310 nm emission wavelengths wi th a detection limit of 5 ng/mL for dobutamine. This procedure was app lied to ascertain the pharmacokinetics of dobutamine infusion in nine patients with cardiogenic shock and end-stage renal disease undergoing haemodialysis.