chromatography..

[km1865]

Quick question.. for a nonpolar sample being run under TLC or column chromatography, does the eluent need to be polar in order to compete with teh number of free particles of the sample binding to the adsorbent, or can a nonpolar solvent be used to end up with experimentally useful results? i.e., since the nonpolar sample will not even interact with the strongly polar stationary adsorbent, cant any eluent be technically used, or does the eluent have to be polar in order to bind with the stationary adsorbent? Thanks!

---

Members don't see this ad.

 

[whiteshadodw]

Quick question.. for a nonpolar sample being run under TLC or column chromatography, does the eluent need to be polar in order to compete with teh number of free particles of the sample binding to the adsorbent, or can a nonpolar solvent be used to end up with experimentally useful results? i.e., since the nonpolar sample will not even interact with the strongly polar stationary adsorbent, cant any eluent be technically used, or does the eluent have to be polar in order to bind with the stationary adsorbent? Thanks!

its a little bit more complicated than that. but if you want good resolution, you want to choose a solvent where the nonpolar sample will have more affinity for the solvent than the plate. but you also want to choose a solvent based on how far the solvent can travel on the plate.

so lets say you get a polar plate, and nonpolar sample mixture along with some polar impurities or reactants (maybe you're monitoring the reaction rate/mixture). you're more likely going to pick a nonpolar 'eluent' since it will travel up the plate faster and since it will elute the nonpolar sample with it.