Fast analysis of catecholamine metabolites MHPG and VMA in human plasma by HPLC with fluorescence detection and a novel SPE procedure

A fast and sensitive high-performance liquid chromatographic method has been developed for the determination in human plasma of MHPG (3-methoxy-4-hydroxyphenylethylenglycol) and VMA (vanillyl mandelic acid), the main metabolites of epinephrine and norepinephrine. Analyses were carried out at 325 nm while exciting at 285 nm on a reversed-phase column (Atlantis C18, 150 mm × 4.6 mm I.D., 5 μm) using a mobile phase composed of 2% methanol and 98% aqueous citrate buffer at pH 3.0. A careful solid-phase extraction procedure, based on mixed-mode reversed-phase - strong anion exchange Oasis cartridges (MAX, 30 mg, 1 mL), was developed for the pre-treatment of plasma samples. Extraction yields were satisfactory, always higher than 90%. Calibration curves were linear over the 0.2-40.0 ng mL⁻¹ concentration range for MHPG and over the 0.5-40.0 ng mL⁻¹ concentration range for VMA. The method was successfully applied to plasma samples of former drug users undergoing detoxification therapy and subjects “at risk” of developing drug addiction.