Interferences by anti-TB drugs in a validated HPLC assay for urinary catecholamines and their successful removal

A validated high performance liquid chromatographic assay for urinary catecholamines is presented. After addition of 3,4-dihydroxybenzylamine as internal standard (IS) to urine, norepinephrine (NE), epinephrine (E), dopamine (DA) are extracted by ion exchange chromatography and eluted with boric acid. After paired ion separation, quantitation is by electrochemical (coulometric) detection after correction of internal standard recovery. Novel interferences by anti-TB drugs on norepinephrine assay are discussed. A simple method for their removal using alumina is presented.