C1.3.4—Photosynthetic pigment separation

Chromatography separates photosynthetic pigments because solvent movement carries pigments different distances according to their solubility and interactions with the stationary phase.

Exam analysis

Chance of appearing4%of analysed past papers

Latest appearanceNovember 2024

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Recent exam appearances

November 2024Paper3 ["SL"] · TZ23(c)[ 1 ]C1.3.4—Photosynthetic pigment separation

November 2024Paper3 ["SL"] · TZ23(b)[ 3 ]C1.3.4—Photosynthetic pigment separation

November 2024Paper3 ["SL"] · TZ23(a)[ 1 ]C1.3.4—Photosynthetic pigment separation

November 2023Paper1 ["SL"] · TZ213[ 1 ]C1.3.4—Photosynthetic pigment separation

May 2021Paper1 ["SL"] · TZ212[ 1 ]C1.3.4—Photosynthetic pigment separation

Coverage 2017–2024 · Updated 15 Jul 2026

Pigments separate because each partitions differently between a moving solvent and the stationary phase. A pigment that is more soluble in the solvent and less strongly attracted to the stationary phase moves farther.

A pigment chromatogram labels the origin, pigment distance and solvent-front distance used to calculate Rf.

$R_f = \frac{d_{pigment}}{d_{solvent\ front}}$

Extract pigments in an organic solvent and place a concentrated spot on the origin.
Keep the origin above the solvent; let the solvent rise.
Mark the solvent front immediately, then measure from the origin to each spot's centre.
Compare colour and Rf only with standards run under the same solvent, temperature and stationary phase.

light energy → excited pigment electrons → ATP and reduced NADP → CO₂ reduced using hydrogen from water → organic carbon compounds; photolysis of water releases O₂

A chromatogram separates pigments; Rf compares their movement under matched conditions.
An absorption spectrum measures captured wavelengths; an action spectrum measures whole-process rate.
A limiting-factor experiment changes one condition, controls the others and measures O₂ production or CO₂ uptake per unit time.

When a rate curve plateaus, identify which factor was relieved and which may now be limiting. When evaluating CO₂ enrichment, separate strong control from ecological realism and do not extrapolate beyond the tested conditions.

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Describe the process used to obtain this chromatogram.

Concept essentials

Chromatography separates pigments because they move different distances with the solvent.
Rf equals pigment distance from the origin divided by solvent-front distance from the origin.
Known Rf values and colours help identify separated pigments.
Organic solvents extract photosynthetic pigments from leaf or algal tissue.