Determination of Uric Acid in urine sample

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BACKGROUND

Uric acid is the end product of Purine and nucleolide metabolism, which occurs in kidney and small intestine. Normal range of uric acid, the level is 0.5 – 1 g for every 24 hours.

The aim is to determine the presence of uric acid in the given sample of urine.

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REQUIREMENTS

Chemicals:    2% Sodium Carbonate solution

Silver Nitrate solution

Benedict’s Reagent

20% Sodium Carbonate Solution

Conc. Nitric Acid

Liquor Ammonia

5% Sodium Hydroxide (NaOH)

Apparatus:    Test Tube

Burette

China Dish

Filter Paper

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PROCEDURE

Schiff test

A small amount of urine is treated with 2% Sodium Carbonate. Moisten the filter paper strip with Silver Nitrate solution. Add 1 – 2 drops of mixed urine sample to the filter paper.¹

Benedict’s test

The blue colour tungstous acid is reduced from phosphor tungstic salt by uric acid, in an alkaline medium.

Experiment procedure

3 ml of urine sample is taken in a test tube along with it add 1 ml of Benedict’s reagent, 2 ml of 20% Sodium Carbonate Solution. Mix all the contents by shaking well in hands. (Caution note: Benedict’s Reagent is a vigorous and poisonous reagent; to be used only with burette).^1,2

Murexide test

The Alloxantin is formed by condensing Dialuric acid and Alloxan. The Dialuric acid is formed from oxidizing uric acid. The Purpuric acid is formed as a result of Ammonim Hydroxide reacting with Alloxantin. The formation of ammonium purpurate (Murexide) gives the reddish purple colour.

Experiment procedure

2 – 4 drops of nitric acid is added to 5- 8 drops (1 ml) of sample urine are heated to ensure that every trace of nitric acid and water are evaporated and reddish Purpuric Acid is acquired. Add few drops of Liquor Ammonia which forms Ammonium Purpurate, turning the deposits to reddish violet colour. Add 5% Sodium Hydroxide.²

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CONCLUSION

The colour of the filter paper turns to dark brown or black in Schiff test. The colour of the solution turns blue which confirms the presence of uric acid in urine in Benedict’s test. In murexide test, the reddish-brown turns reddish violet in turn into Bluish Violet confirming the presence of uric acid.

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REFERENCES

1. Mohanty & Basu; Fundamentals of Practical Clinical Biochemistry; 37.
   
2. Joshi A. Rashmi; A Textbook of Practical Biochemistry; 2002: 41.