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 L-Dopa at least 72 hours before and during collection.
HPLC-EC
3 days',pre_test_info=strictly avoid L-Dopa at least 72 hours before and during collection.