Chromatography separates photosynthetic pigments because solvent movement carries pigments different distances according to their solubility and interactions with the stationary phase.
Coverage 2017–2024 · Updated 15 Jul 2026
Photosynthetic pigments can be separated and identified because they differ in solubility in the mobile solvent and attraction to the stationary phase.
Extract pigments, place a small concentrated spot on paper or a thin-layer plate, keep the spot above the solvent, allow the solvent front to rise, then mark the solvent front immediately and observe the separated bands.
If a pigment travels 4.2 cm while the solvent front travels 6.0 cm, Rf = 4.2 ÷ 6.0 = 0.70. Identify a pigment using both its colour and an Rf reference obtained with the same solvent and stationary phase.
Rf has no unit and normally lies between 0 and 1. It depends on the solvent and stationary phase, so an Rf from different conditions is not a secure identification; band distance alone is not pigment abundance.
This objective is assessed through structured response, commonly using Identify / State / Outline.
Identify / State / Outline / Describe / Explain
Build the answer around this relationship: Chromatography separates pigments because they move different distances with the solvent.
Representative question
Describe the process used to obtain this chromatogram.
Photosynthesis converts light energy into chemical energy in carbon compounds. Carbon dioxide is reduced to carbohydrate using hydrogen from water, glucose is the main stored product, and released oxygen comes from photolysis of water. Pigment evidence is tested with chromatography and Rf, spectra questions separate absorption from action, and rate/evidence questions use limiting factors, controls, and CO2 enrichment context.
