Urinalysis - The Carter Center

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Procedure
1. Prepare fresh solution of sodium nitroprusside by shaking few
crystals of sodium nitroprusside in 10 ml of distilled water.
2. Add 0.2 ml aqueous sodium nitroprusside to 5ml urine
3. Add 0.5 ml of 40% sodium hydroxide. During this time the urine
turns red due to the action of creatinine and other interfering
substances.Add 3.5ml of 30% glacial acetic acid, and the color
may change to blue or dark if melanin present which is indication
for a positive reaction.
C. Oxidation by Atmospheric Air
Allow the urine sample to stand exposed to the air undisturbed for 24
hours. If melanogen presents, it will slightly oxidize to melanin by the air,
and turns dark brawn or black from the top downwards.
• Homogenstic acid gives the same effect, but the darkness of
melanogen is not accelerated appreciably by alkali.
* Microscopic examination of sediment for melanin cast is also possible.
Exercises:
1. Discuss by comparison the Benedict's Qualitative and Glucose
oxidase Tests.
2. List down the possible substances, which give false positive
results in non-specific tests for glucose determination.
3. Mention the physiological effects of ketone accumulation in blood.
4. Write the principle of the test for determination of bilirubin and
hemoglobin.
5. Write the general principles for the two types of determination of
urinary protein.