Organic Chemistry Laboratory Essay

1880 Words Aug 18th, 2012 8 Pages
CHEM 333L
Organic Chemistry Laboratory
Revision 1.1

Isolation of Lycopene from Tomato Paste using Column Chromatography
In this laboratory exercise we will isolate the pigment Lycopene from tomato paste. In a follow up lab, we will examine the UV-VIS spectrum of Lycopene, isomerize it and then examine the isomer’s spectrum for comparison.

Lycopene, the red pigment of the tomato, is a C40-carotenoid made up of eight Isoprene units; making it a tetraterpene.

Other sources of the compound include:
Vegetable Source
Gac
Tomato
Tomato Juice

µg Lycopene per Gram Wet Weight
2000 – 3000
8.8 – 42
86 – 100

Page |2

Tomato Sauce
Tomato Ketchup
Watermelon
Pink Grapefruit
Pink Guava
Papaya

63 – 131
124
23 – 72
…show more content…
It is essential that the components move through the column as a narrow horizontal band in order to come off the column in the least volume of solvent and not overlap with other components of the mixtures. Therefore, the column should be vertical, and the packing should be perfectly uniform, without voids caused by air bubbles.
The preferred method for packing silica gel and alumina columns is the slurry method, whereby a slurry of the adsorbent and the first eluting solvent is made and poured into the column. When nothing is known about the mixture being separated, the column is prepared in ligroin or hexanes, the least polar of the eluting solvents.
We will extract crude Lycopene from tomato paste and apply the extract to our column. Tomato paste, as a source for our Lycopene, has the advantage that its Lycopene concentration is significantly higher, gram for gram, than that of a ripe tomato. The main drawback of using tomato paste is that trans-Lycopene may isomerize during the cooking process during which the paste is produced. We will then pack a column for purifying the Lycopene. We will use neutral
Alumina (Grade II-III), a fairly active adsorbant, to separate the Lycopene from other tomato paste pigments.
Lycopene, with its 13 double bonds, is attracted to alumina more strongly than are
β-carotene

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