Page 25 - Practical Handout bio 2 mnu 2025_Neat
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Level two – Semester 4 - PharmD Biochemistry-II PB-403 (Practical course) 2024/2025
Preservation of urine Specimen:
1. Urine samples must be tested in the laboratory within 2 hours of
collection to get the correct results.
2. Refrigeration (4-6°C): is the best general method of preservation of
urine samples for up to 8 hours.
3. The following chemical preservatives can be added to the 24-hour
urine sample:
HCl It is used for the preservation of a 24-hour urine sample for
adrenaline, noradrenaline, and steroids.
Toluene It forms a thin layer over the surface and acts as a physical
barrier for bacteria and air.
Thymol It inhibits bacteria and fungi.
Formalin It is an excellent chemical for the preservation of formed
elements.
Changes that occur in standing urine at room temperature:
Due to the production of ammonia from urea by
Increase in pH
urease-producing bacteria.
Crystals Due to the precipitation of phosphates and calcium
formation (making the urine turbid).
Loss of ketone Since they are volatile.
bodies
Decrease in Due to glycolysis and utilization of glucose by cells
glucose and bacteria.
Bacterial proliferation and Disintegration of cellular elements
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