Jun 15, 2017
90
16
Status
Pre-Dental
will thhe most nonpolar substance always elute first in column chromatography? I just got a question where ether is on silica gel. I thought 1-butanol would elute first (vs. nonpolar ether) because it is most polar out of given choices, but the answer is cyclohexane (most nonpolar). I'm thinking the silica gel is the thing that is polar, and any solvent included with it can be disregarded essentially; is that true?
 

Clight96

2+ Year Member
Mar 9, 2017
50
111
Status
Pre-Dental
will thhe most nonpolar substance always elute first in column chromatography? I just got a question where ether is on silica gel. I thought 1-butanol would elute first (vs. nonpolar ether) because it is most polar out of given choices, but the answer is cyclohexane (most nonpolar). I'm thinking the silica gel is the thing that is polar, and any solvent included with it can be disregarded essentially; is that true?
Silica gel is extremely polar and so the most polar substance will stick harder (like-like), therefore it will elute last, because it is held so tightly onto the gel. The opposite logic applies for the least polar substance, therefore the most nonpolar substance will always elute first. Solvent can be disregarded unless it directly asks something involving it, like ether vs. hexanes, etc
 
OP
D
Jun 15, 2017
90
16
Status
Pre-Dental
Silica gel is extremely polar and so the most polar substance will stick harder (like-like), therefore it will elute last, because it is held so tightly onto the gel. The opposite logic applies for the least polar substance, therefore the most nonpolar substance will always elute first. Solvent can be disregarded unless it directly asks something involving it, like ether vs. hexanes, etc
Will there be any substances besides silica gel that I may see on the DAT that I should know of? Or will the column always be polar so it wouldnt matter regardless
 
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