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50 mL (10 mL min.) aliquot of 24-hour urine. Add 25 mL of 50% acetic acid as preservative at start of collection. Use 15 mL of 50% acetic acid for chioldren less than 5 years old. This preservative is intended to achieve a pH of between approximately 2 and 4. Record 24 hour volume on test request form and urine container.