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Caraway Method for Uric Acid

Caraway method for uric acid post we briefly summarise about: principle, reagents requirements, procedure, result, application and limitations of caraway method.

Caraway Method, Blood contains uric acid, which is a waste product. It’s made when the body breaks down purines, which are compounds. The majority of uric acid is dissolved in the blood, passed via the kidneys, and excreted in the urine. Purine-rich foods and beverages raise uric acid levels as well.

Principle

The Caraway method is based on uric acid oxidation in a protein-free filtrate, followed by phosphotungstic acid reduction to tungsten blue. The intensity of blue hue, which is directly proportional to the concentration of uric acid in serum and measured at 660 nm, is directly proportional to the concentration of uric acid in serum (red filter).

Requirements

Materials

1. Spectrophotometer

2. Standard flasks

3. Test tube

4. Test tube Stand

Reagents

1. 14% Sodium carbonate

2. Distilled water

3. Lithium carbonate

4. Phosphoric acid

5. Sodium tungstate

6. Uric acid

Reagents

Uric acid

Dissolved 5g of sodium tungstate in 400 ml of distilled water. Added 40ml of 84% phosphoric acid and refluxed gently for 2 hours. Cooled, transferred to 50ml standard flask and made up to the mark with distilled water. Stored the reagent in a brown bottle.

Stock standard

Weighed about 100mg of uric acid in a small beaker. Also weighed 60mg of lithium carbonate into the beaker. Added 15-20ml of water heated the solution to about 60 degree Celsius and poured into 100ml standard flask and made up to the mark with distilled water.

Working standard

Diluted 2ml of stock standard to 100ml with water. 1ml of the working standard containing 20µg of uric acid.

Procedure

1. In to different test tubes pipetted out 0.5, 1.0, 1.5, 2.0, 2.5ml of working standard corresponding to the µg values 10-50 respectively and made upto 3ml with distilled water.

2. The given unknown solution was made up to 100ml with distilled water. From this 20ml was taken for the experiment. This was made up to 3ml with distilled water.

3. To all the tubes added 1ml of uric acid reagent follower by 1ml of 14% sodium carbonate solution and let it stood for 15minutes and the blue colour developed was read in the colorimeter at 640nm against a reagent blank.

4. A standard graph was drawn by plotting the concentration of uric acid on the x-axis and colorimeter reading on y-axis. From Caraway method the concentration of uric acid present in the unknown solution was calculated.

Calculation

The amount of uric acid present in 100ml of the given sample is ————— mg/dl.

Further Readings

Reference