Electrochemical detection of catecholamines in urine and plasma after separation with HPLC

The catecholamines in plasma and urine were determined by electrochemical detection after separation on a HPLC column RCM 100 C 18. Linear calibration plots of epinephrine, norepinephrine and dopamine have been obtained in the range expected to appear in urine or plasma. Coefficients of variation (0.5 to 10%), recovery rates (60 to 80%) and the standard deviation were satisfactory, whereas plasma dopamine showed a greater variation (10-15%). The values ascertained by this technique were compared with those determined by the radioenzymatic assay of Da Prada et al. They showed a good correlation for norepinephrine r = 0.92, p less than 0.001 and epinephrine r = 0.80, p less than 0.01, but less for dopamine r = 0.1. Experimental details of isolation from plasma with Al2O3 adsorption and desorption with HClO4, and from urine with ion exchange chromatography on Bio-Rex 70 and elution with boric acid are described. Technical modifications which improve the method are reported. The optimized assay could reliably be employed in investigations of more than 3000 urine and plasma samples obtained from patients and athletes before and after exercise.