laboratory diagnostic - toxicology - Oxalic acid - urines, ®, Acidified 24hr urine (pH 2-3), 50ml. Urine acidification: Urines are to be stored in the refrigerator during the sample collection. The acidification should be performed by the referring laboratory by adding Hydrochloric acid (HCl) 12N to obtain a pH between 2 and 3 (5 to 20 mL of acid depending on the total urine volume and the initial sample pH; Mix the urine well before dividing into aliquots. Specify diuresis. Chemistry - Spectrophotometry, ssso, todylaboratories®, bmn, code L16LD2210