Spinach Column Chromatography Lab Report

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This experiment aims to identify the pigments in spinach using column chromatography. The two categories of pigments which exist in spinach are carotenoids and chlorophylls. β-Carotene is non-polar and is a series of repeated isoprene units, see Figure 1 for structure. It varies from α-Carotene by the double bond on the left carbon ring which is shifted over to the left by one set of carbons in α. The chlorophylls are also similar; however, β has a higher polarity than α. Their structures are displayed below in Figure 2; they have more rings and integration of non-carbon elements than carotene molecules which makes them the more polar pigments. The nitrogen and magnesium bring new electronegativity into the structure and are the primary drivers of the polarity increase. Polarity occurs when charge, electronegativity, in unbalanced in a molecule and it greats a dipole. This dipole develops a positive and negative side which increases it willingness to interact with other molecules, especially those with dipoles. These are intermolecular forces, IMF, and they are listed from strongest to weakest: ionic, hydrogen-bonding, dipole-dipole, London dispersion. Ionic forces come from salts such as NaCl. Interactions outside of ionic forces are under …show more content…

There were two collection of green pigments which were combined before the TLC testing. This combination could have introduced the xanthophylls to the chlorophylls. Because the two pure greens were not tested separately it cannot be known whether we eluded are different point, indicating their different polarities. Additionally, the column is delicate and needs to be wet at all times, this can cause errors because there is solvent mixing during the transitions which is inevitable. However, this mixing can be minimized by not allowing the solutions to mix at the top of the column through adding a new solvent only once the old one is below the top of the

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