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a sample mixture of ethyl benzoate and dodecane is injected on two GC columns. Column A...

a sample mixture of ethyl benzoate and dodecane is injected on two GC columns. Column A has DC710 silicone oild as the stationary phase, and column B uses polyethylene glycol as the stationary phase. Which substance would be certain to elute first from column A and would the same material be expected to elute first from column B? Which column, A or B, would be expected to give the better seperation of these two substances?

Solutions

Expert Solution

Silicon oil and Polyethylene glycol both have polymeric structure having ether linkage. But the basic difference is the end gruop. In silicon oil the end group is an alkyl group. But in Polyethylene glycol the end group is hydroxyl group. Thus Polyethylene glycol is more polar than that of silicon oil.

Depending on this it can be concluded that dodecane(non-polar substance) will be eluted first in both of the columns. Ethyl benzoate is more polar tha dodecane and will prefer to bind with polar staionary phase. so it will elute at last in both columns.

The Polyehylene glycol will be better stationary phase as a result of the functional group present in it as mentionted earlier. It will bind ethyl benzoate more effectively . Hence column B will give better sepation.

queen_honey_blossom answered 2 years ago
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