OSAZONE TEST - For differentiation of reducing sugar

Osazone test is performed to differentiate the reducing sugars on the basis of crystal formation.

Table of Contents

REAGENTS:

1. Phenylhydrazine mixture consisting of:

i. Phenylhydrazine, and

ii. Anhydrous sodium acetate.

2. Original solution (0.8.) – containing a carbohydrate

PRINCIPLE:

Aldehyde or keto group containing sugars reacts with the amine group of phenylhydrazine to give phenylosazone.

PROCEDURE:

Take phenylhydrazine mixture and till about half an inch of the test tube with it.
Add 3 to 5ml of sugar solution (original solution) to the test tube.
Mix thoroughly and place it in a boiling water bath.
Note the appearance of a yellow crystalline precipitate in the test tube.
Remove and allow the test tube to cool slowly.
Do not cool the test tube under tap water.
Examine the crystals under the microscope and make a drawing.
Draw only what you see.

NOTE:

Osazones of glucose are formed in 10-15 minutes whereas those of disaccharides take up to 45 minutes. Sucrose does not react with phenylhydrazine to form crystalline compounds called osazones.

Observation and Result:

SUGAR	OSAZONE	SHAPE
Glucose	Glucosazone	Needle-shaped
Fructose	Fructosazone	Needle-shaped
Galactose	Galactosazone	Fluffy ball shaped
Lactose	Lactosazone	Fluffy ball shaped
Maltose	Maltosazone	Sunflower shaped