Specimen: 50 mL (10 mL min.) aliquot of 24-hour 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 L-Dopa at least 72 hours before and during collection. Stability (Room): 8 hrs Stability (Refrigerated): 7 days Stability (Frozen): 30...