In chromatography, what is the role of a locating agent?

• A. To reveal colourless substances on chromatographic spots
• B. To change the color of amino acids
• C. To speed up separation
• D. To fix spots

Answer: (A)

Locating agents are used to detect and visualize substances that may be colorless after the chromatogram is developed. Many components don’t leave visible spots on their own, so applying a locating agent chemically reacts with the substances to produce a visible color or glow. This makes the spots easy to see, allowing you to determine their positions and calculate Rf values to identify the components. They aren’t about speeding up the separation or fixing the spots. So the correct idea is that the locating agent reveals colourless substances on chromatographic spots.