TEST FOR UROBILIN IN URINE

UROBILIN :- Urobilins are oxidation products of urobilinogen. Urobilins are orange-coloured and are responsible for the normal colour of the urine, whereas urobilinogen is colourless. Urobilin does not react with Ehrlich's reagent, but reacts with Schlesinger's zinc acetate reagent.

Schlesinger's Test for Urobilin (Urobilinogen + Urobilin)

Principle Urobilinogen is oxidised to urobilin with tincture of iodine. When mixed with alcoholic zinc-acetate solution, zinc-urobilin is formed which shows a green fluorescence. 
 

Reagent 1. Tincture of iodine Prepare a saturated solution of iodine in 70 % ethanol

2. Zinc-acetate reagent Prepare a saturated solution of zinc-acetate in absolute ethanol. 

Procedure 1. To about 10 ml of urine in a test tube add a few drops of tincture of iodine

2. In another test tube, place about 10 ml of zinc-acetate reagent.

3. Mix the two solution by pouring from one tube to another, backwards and forwards,several times (10-12 times)

4. Filter the mixed solution through Whatman No. I filter paper.

5. Examine the filtrate for green fluorescence by viewing from above against a dark back ground and passing through the direct rays of a fairly strong light. The fluorescence is more easily detectable under ultraviolet light. Results Normal urine gives a very mild fluorescence. The test is reported as positive, negative or increased.

Note

1. Bilirubin, if present, must be removed from the urine as for theurobilinogen test.

2. The test can be performed for the detection of urobilin only, if the first step of oxidization with iodine is omitted.