Evaluation of sample work-up methods and internal standards for the determination of catecholamines in urine by HPLC with electrochemical detection.

Two sample work-up methods: (I) one consisting of adsorption of the catecholamines onto alumina followed by ion pair extraction and (II) another consisting of isolation by cation exchange and subsequent adsorption onto alumina, have been evaluated for the assay of urinary catecholamines by means of HPLC with electrochemical detection. With the aim of achieving high precision, two internal standards, i.e. dihydroxybenzylamine and epinine, have been compared. The results indicate that clean HPLC chromatograms are obtained with both work-up methods and that the highest precision (RSD < 4%) is achieved with method II and with epinine as internal standard, whereas the lowest precision is obtained with method I and with dihydroxybenzylamine.