Figure 8. Detection of major chemical functional groups by color reactions.

(A) Organic acid color reaction (0.05% BPB - ethanol solution): The BPB was used to detect the carboxylic acid group, along with yellow color change. (B) Ninhydrin color reaction: The existence of amide groups can induce mulberry color change in Ninhydrin color reaction. (C) Dragendorff color reaction: The compound, containing nitrogen atoms, can cause orange or yellow color change in Dragendorff color reaction. However, there are not any color changes when the nitrogen atoms are in the form of amide groups or not in existence.