Plants have several different photosynthetic pigments in their chloroplasts. (a) A student separated and identified the chloroplast pigments present in a leaf extract from a spinach plant using two slightly different methods. Method A • A type of chromatography known as thin layer chromatography (TLC) was used to separate the pigments. • A mixture of ether and cyclohexane was used as a solvent in TLC. Method B • The student repeated TLC but treated the spinach leaf extract with a chemical. The chemical causes a magnesium ion in a pigment to be replaced by two hydrogen ions. • The student used a leaf from the same spinach plant, and used the same solvent as in method A. The student calculated R values and compared these to reference values to identify the pigments. [Figure 3.1] shows the results for method A and method B.