||50 mL (10 mL min.) aliquot of 24-hour urine. Collect urine with appropriate volume of 50% HCl to maintain pH between 1–2. Do not use concentrated HCl. Record 24 hour volume on test request form and urine container. Ship refrigerated or frozen. Patient should strictly avoid Alpha- Methyldopa, Buspirone, Codeine, Isoproterenol metabolite, Mandelamine, L-dopa, Parcetamol, Metoclopramide, pepper, alcoholic beverages, tea/coffee, tobacco and strenuous exercise at least 72 hours before and during specimen collection.