Chemical change often take place in urine when the are left standing at room temperature for a long period of time. Below are some of the change;
- Urea breakdown to ammonia via bacteria action, as such resulted in raising of urine pH.
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Urobilinogen is oxidized to urobilin when urine is left to stand at room temperature for long time.
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Glycolysis take place as result of bacteria action.
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Urates precipitation take place in acidic urine.
In other to prevent the change not to take place in urine, the urine sample should be preserved in the refrigerator at 4°C. Chemical are also used to preserved urine specimens, mostly the specimens that are to be keep for 24hours before analysis.
Chemical preservatives
There are that often used to preserved urine sample, some of the chemical are;
- Concentrated hydrochloric acid (conc.HCl) ; 10ml of Conc. HCl is used to preserved urine specimens that is to keep for the next 24hours before analysis. But note that sample for estimations of protein or urate should not be acidified, such sample should store in the refrigerator, or preserved with thymol.
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Thymol and other chemical; thymol is crystal in nature. Little quantity of it to preserved urine specimens for estimation of total protein and creatinine. Other chemicals are chloroform which are used to preserved urine when the urine are to be subjected for chemical investigation. Boric acid is used to preserved urine which is collected for examination of bacteria infection.
Keeping large volume of urine for 24 hours, often yield problems, as such it is advisable to keep small representative portion of the urine instead of the whole urine collected.
To collect representative of urine sample from the whole sample, mix the urine thoroughly and carefully measure specific volume of urine to represent the whole sample, make sure to note the volume measure. Discard volume at list into 4 small universal bottle, label with the patient details I.e.
Patient name, age, sex, date of collection, time of collection, and test requested.
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