Test For Presence Of Sugar In Urine

Aim

To perform a test detecting the presence of sugar in the given sample of urine.

Theory

Urine is a liquid waste that is produced by the kidney which needs to be eliminated from the body. Through the process of urination, urine is excreted from the urethra. In humans, urine is a yellowish liquid containing water and several other chemical components such as uric acid, urea, traces of enzymes, hormones, and carbohydrates.

Properties Of Urine

  • It has a characteristic pale yellow color
  • The yellow color is imparted by the yellow pigment known as urochrome
  • The urine pH ranges from 4.6 to 8
  • More than 95% of urine constitutes water
  • Organic substances of nitrogenous origins found in urine are creatine, uric acid, urea.
  • Other organic matter in urine are lactic acid, oxalic acid
  • Inorganic constituents are potassium chloride, sodium chloride, phosphates, and sulphates.
  • Urine abnormally can contain other constituents such as ketone bodies, sugar(glucose), protein, bile and blood
  • Glucose is usually not found in urine. It appears when in blood, the glucose levels exceed the renal threshold of glucose i.e., 160 to 180 mg/dl.
  • When glucose is present in urine it is termed as glucosuria. It indicates diabetes mellitus.

Sugar presence in a sample of urine can be detected by performing the following two tests:

  • Benedict’s test
  • Fehling’s test

What is Benedict’s Test?

A Benedict’s solution serves as a reagent in this test. The reagent is a blend of copper, sodium citrate and sodium carbonate and copper II sulphate pentahydrate (CuSO4.5H2O)

What is Fehling’s test?

In this test, the reagents are

Fehling’s solution – A: Aqueous solution of copper II sulphate – Has a blue color

Fehling’s solution – B: Aqueous solution of sodium potassium tartrate – Colourless and clear

When the urine sample is boiled with reagents, the CuSO4 found in Benedict’s and Fehling’s solution is reduced by the reducing agent, glucose for the formation of a colored cuprous oxide precipitate.

Depending on the glucose concentration, a yellow, green and brick-red formation of precipitates of oxides take place.

The table below depicts the color sequence on the basis of glucose level concentration.

Sugar level (Percentage)

Precipitate color

Absence of sugar

Blue

0.5%-1%

Green

1%-2%

Yellow

2% or higher

Brick red

1. Benedict’s Test

Material Required

  • Benedict’s solution
  • Test tube
  • Test tube holder
  • Measuring cylinders
  • Urine sample
  • Burner

Procedure

  • From the urine sample bottle, using the measuring cylinder, accurately take a 2ml sample of urine.
  • Add the sample to a test tube
  • Using a measuring cylinder, accurately take 5ml of Benedict’s reagent
  • To the tube containing the sample of urine, add Benedict’s reagent
  • Test tube should be held securely with the test tube holder to heat it on the burner for 2 minutes
  • While it is heating, keep stirring the tube continuously
  • Observe the changes

Observation And Conclusion

Upon heating the sample, gradually, a yellow precipitate becomes apparent. This indicates that the given sample of urine contains sugar. Different precipitates are formed depending upon the sugar concentration in urine which can be yellow, green, brick red.

2. Fehling’s Test

Material Required

  • Fehling’s solution A
  • Fehling’s solution B
  • Test tube
  • Test tube holder
  • Urine sample
  • Measuring cylinder
  • Burner

Procedure

  • From the urine sample bottle, using the measuring cylinder, accurately take a 2ml sample of urine.
  • Add the sample to a test tube
  • Using a measuring cylinder, accurately take 2ml of Fehling’s solution A
  • To the tube containing the sample of urine, add Fehling’s solution A
  • Using a measuring cylinder, accurately take 2ml of Fehling’s solution B
  • To the tube containing the sample of urine, add Fehling’s solution B
  • Test tube should be held securely with the test tube holder to heat it on the burner for 2 minutes
  • While it is heating, keep stirring the tube continuously
  • Notice the changes

Observation And Conclusion

On heating the sample, the presence of sugar is indicated in the sample of urine when a green precipitate is apparent. Different precipitates are formed depending upon the sugar concentration in urine which can be yellow, green, brick red.

For more information on related biological concepts and experiments, please register at BYJU’S.

Related Links:

Leave a Comment

Your email address will not be published. Required fields are marked *