Fouchet's test for bilirubin IN URINE

Fouchet's test 

Principle- Barium chloride reacts with sulphate radicals in the urine to form a precipitate of barium sulphate. Available bile pigments adhere to the precipitate and are detected by oxidation of bilirubin which is yellow, to biliverdin which is green, on treatment with ferric chloride in the presence of trichloroacetic acid. 

Reagents

1.10% barium chloride (w/v)

 2. Fouchet's reagent:

 Trichloroacetic acid          25 g

            Distilled water                     50 ml

10% ferric chloride            10 ml Diluted to 100 ml with distilled water.

Procedure- 1. Determine the pH of the urine. If alkaline,acidify with 33% acetic acid.

 2. Add 5 ml of 10% barium chloride to 10 ml of urine. Mix well. If the precipitate produced is insufficient, add a drop of dilute sulphuricacid or ammonium sulphate solution.

3. Filter through Whatman no. 1 filter paper.

4. Carefully unfold the filter paper and place it on the top of a dry filter paper. Add 1 drop of Fouchet's reagent on the precipitate in the centre of the wet filter paper. A green colour is produced if bile is present. The amount of bilirubin in the urine is proportional to the intensity of the green colour.

Note

1. Salicylates will produce pink or mauve colour, so ignore such colour.

2. Bilicyanin will form a blue colour.