Why are amino acids detectable using the Ninhydrin test?

Which intermediate is formed during the Ninhydrin reaction with amino acids?

Analyze the stoichiometry of the Ninhydrin reaction. Why is it necessary to have two Ninhydrin molecules per amino acid?

What is the role of Sodium Hydroxide in the Ninhydrin test?

Which step in the Ninhydrin reaction mechanism specifically leads to the formation of the chromophore responsible for the color change?