||50 mL (10 mL min.) aliquot of random urine. Add 50% HCl drop by drop to bring the pH between 1–2. Do not use concentrated HCl. Ship refrigerated or frozen. Patient should strictly avoid Alpha-Methyldopa, Buspirone, Codeine, Isoproterenol metabolite, Mandelamine, L-dopa, Paracetamol, Metoclopramide, pepper, alcoholic beverages, tea/coffee, tobacco and strenuous exercise at least 72 hours before and during specimen collection.