Experiment 69

Objective

To identify the presence of proteins in a sample using the Ninhydrin test.

Introduction

When amino acids, dipeptides, or protein solutions are heated with dilute aqueous ninhydrin, a violet-colored complex forms, indicating the presence of proteins or amino acids.

Materials

Chemicals

●      Protein solution

●      Ninhydrin solution

●      Distilled water

Apparatus

●      Two test tubes

●      Two test tube holders

●      Dropper

●      Bunsen burner

Reagents

●      Dilute ninhydrin reagent prepared in one test tube

●      Dilute protein solution in another test tube

Procedure

1.    Place the protein solution in a test tube and secure it in a test tube holder.

2.    Add a few drops of the ninhydrin solution to the test tube.

3.    Heat the mixture for 5–6 minutes using a Bunsen burner.

4.    Stop heating once a color change is observed.

Observation

A violet color develops in the solution, indicating the presence of protein.

Questions

1.    What is ninhydrin?

2.    What is a protein?

3.    What color develops in the Ninhydrin test?