Question

A mixture of lipids is applied to a silica gel column, and the column is then washed with increasingly polar solvents. Arrange the lipids in order of elution by placing the first lipid to elute at the top. Eluted first cholesterol ester diglyceride sphingosine phosphatidic acid phosphatidylcholine Eluted last

Answer 1

The question is difficult to answer since it remains unclear as to what type of chromatography technique the lipids are exposed to. If we think in a more generalized way that the lipids are separated from a mixture and the separation is based on the level of binding since the column is said to be washed with increasingly polar solutions. So, it becomes clear that the lipids inside the column interact and depending on the level of interactions they are eluted when they are exposed to polar solvents.

Considering the structure of the lipids, the highest level of interactions is available to phosphatidic acid, phosphatidylcholine, diglyceride, etc. They interact through ionic interactions between negative charge groups and depending upon how strong the interaction a more polar solution would be needed to disrupt that interaction.

The lipids to be eluted in the order of first to last

sphingosine

cholesterol ester

Diglyceride

phosphatidic acid

phosphatidylcholine

Note: The structure of the lipids are not provided since they are very complex and not easy to draw without a hand I hope you can find them in your textbook. The answer is based on the presumption that the chromatography employed here is ion-exchange chromatography if that turns out to be false then the answer would not remain the same and I would ask you to refer that in the comment section, so that I may change the answer. For any query feel free to ask in the comment section & I will get back to you.