Separation of Chlorophyll a, Chlorophyll B, and Beta Carotene by Paper Chromatography

Topics: Color, Chemical polarity, Chromatography Pages: 4 (1323 words) Published: November 3, 2012
Pigments extracted from different greens have different polarities and may be different colors. Mixed pigments can be separated using chromatography paper. Chromatography paper is able to separate mixed pigments due to their polarity and solubility. Pigments of chlorophyll a, chlorophyll b and beta carotene will be separated on chromatography paper because each has its own polarity and solubility, which results in different distance traveled up the paper. Beta carotene is non-polar so it travels the highest distance, followed by chlorophyll a. Chlorophyll b is the most polar; therefore, it travels the shortest distance. The separated pigments on the chromatography paper can be eluted in acetone and absorbance spectrum is determined using spectrophotometer. Spectrophotometer produces a graph of the absorbance spectrum which shows the wavelengths (in nm) that are absorbed by the pigment and that are reflected. The reflected wavelength of chlorophylls a and b reflect the wavelengths of l light that are associated with green, which gives them their color. Beta carotene reflects the wavelengths that are associated with orange color, and that explains its color. Introduction

Chromatography paper can be used to separate mixed chemicals, including mixed chloroplast pigments prepared from extract from fresh green grass or spinach. The mixture of pigments was prepared from organic greens, which were cleaned, cut into small pieces and bathed in acetone overnight (S. W. Jeffrey). The different pigments, chlorophyll a, chlorophyll b, and beta carotene have different polarities, due to which the separation of these pigments is possible with chromatography paper. Beta carotene is non-polar, chlorophyll b is the most polar, chlorophyll a is more polar than beta carotene, but less polar than chlorophyll b. Chlorophyll a has a methyl group in its structure where chlorophyll b has an aldehyde; this difference results in different polarities (Lampman). Chromatography...
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