Separation and Identification of Photosynthetic Pigments in Spinach Leaves

Separation and Identification of Photosynthetic Pigments in Spinach Leaves

Introduction

All organisms require energy to complete metabolic processes within their cells. In plants, protists, and cyanobacteria, the energy needed to carry out metabolism is acquired through the process of photosynthesis. This process captures light energy from the sun and converts it to glucose and oxygen (Henderson et al., 2010). During photosynthesis, pigments within photosynthesizing parts of the plant, called chloroplasts, participate heavily in absorbing light. In spinach leaves, the four prominent pigments that contribute to photosynthesis include: chlorophyll-a, chlorophyll-b, beta-carotene, and xanthophyll. To separate these pigments, paper chromatography will be used. To hypothesize about the experiment, the group members questioned whether or not paper chromatography would sufficiently separate the pigments in the spinach extract. Paper chromatography is the process that separates compounds based upon the compound's polarity and solubility (Chang, 2007). In this experiment, the paper or plate used in paper chromatography is made up of polar substances. The solvent used (petroleum ether and acetone) is slightly non-polar. The pigments then, will either be dissolved in the plate and develop as a band near the bottom of the plate (the origin) or be dissolved in the solvent and carried with the solvent front, developing as a band towards the top of the plate. The group that will carry out the experiment of paper chromatography predicted that the most polar pigment (chlorophyll-b) will form a band closest to the origin, and the most non-polar pigment (β-carotene) will form a band closest to the solvent front. Chlorophyll-a, which is a polar pigment will settle closer to chlorophyll-b, but further from the solvent front from xanthophyll, which is only slightly polar. Again, this experiment will use paper