In the DCPIP test for vitamin C, what happens to DCPIP in the presence of vitamin C?

• A. DCPIP turns blue
• B. DCPIP turns colorless
• C. DCPIP turns red
• D. DCPIP remains green

Answer: (B)

DCPIP is blue when it is in its oxidized form, and vitamin C acts as a reducing agent that donates electrons to the dye. When vitamin C reduces DCPIP, it loses its blue color and becomes colorless. So the presence of vitamin C makes DCPIP turn colorless. If there were no vitamin C, the dye would stay blue. This color change is how the test signals vitamin C activity.