Isolation and Isomerization of Lycopene from Tomato Paste
Goal / Purpose
To extract the carotenoid pigments from canned tomato paste and separate them by column chromatography to obtain a solution that contains lycopene. Then record the ultraviolet-visible spectrum of this solution and analyze it for evidence of isomerization.
List of Materials
4.0g tomato paste
screw cap vial
ring stamd and clamp
50% mixture of acetone and low boiling petroleum ether
5ml extraction solvent
20ml 10% aqueous solution and 20ml of saturated sodium chloride
PEPARING CHROMATOGRAPHY COLUMN
Pack a column for chromatography- ref. OP-21a
clamp column to ring stand over 25ml beaker
close column with cork or rubber stopper
use OP-18c to extract the solid material from the tomato paste extract 3 times w/ successive 10-ml portions of 50% mixture
each time extract through filter paper into small flask
After 3rd extraction, transfer the residue to the filter and wash it with the 5ml extracting solvent; combining the wash liquid with the extracts. Wash combined extracts with 20ml potassium carbonate followed by 20ml of saturated sodium chloride solution. Dry w/ lycopene
Concentrate the pigment solution to a volume of .5ml by evaporation OP-19.
fill chromatography column with hexanes and let liquid drain until its surface just disappears into the sand layer. Transfer the pigment to the top of the column
Keep liquid level in column constant
When yellow carotene band begins to drain out of the column, replace the beaker by the collection vial and elute the lycopene band, collecting a 5.0ml sample of eluate. Use the midband lycopene sample for spectral analysis as soon as possible.
record spectrum midband lycopene sample over the 600-400nm range. Add a drop of .025% iodine solution to the lycopene solution and leave it in...
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