Organic Chemistry Laboratory Essay
Organic Chemistry Laboratory
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:
µg Lycopene per Gram Wet Weight
2000 – 3000
8.8 – 42
86 – 100
63 – 131
23 – 72 …show more content…
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