Analysis of plasma catecholamines by liquid chromatography with amperometric detection using a novel SPE ion-exchange procedure

Simultaneous determination of the three main catecholamines (Epinephrine, Norepinephrine, and Dopamine) has been implemented by means of liquid chromatography with amperometric detector working in oxidation at +800 mV. The chromatographic analysis was carried out on a reversed phase column (C8 Rainin 150 x 4.6 mm ID, 5 pm) with a mixture of methanol and an aqueous solution of 5 mM of citric acid, 20 mg L-1 octanesulfonic acid, and 20 mg L-1 EDTA (pH 2.9) as the mobile phase. An. original solid phase extraction pretreatment of plasma samples was developed using cationic ionic exchange cartridges with carboxypropylic adsorbent. The steps of the SPE procedure were carefully checked and optimal elution was carried out with perchloric acid. High extraction yield values were obtained for all catecholamines with good reproducibility. Linearity was observed in the 0.06-3.00 ng mL(-1) concentration range for all analytes. LOD and LOQ were respectively 0.03 ng mL(-1) and 0.06 ng mL(-1). The method was applied successfully to the analysis of some real plasma samples from young volunteers under experimental psychological stress.