In ion-exclusion chromatography, ions are separated from nonelectrolytes (uncharged molecules) by an ion-exchange column. Nonelectrolytes penetrate the stationary phase, whereas ions with charge of the same sign as that of the stationary phase are repelled by the stationary phase. Because electrolytes have access to less of the column volume, they are eluted before nonelectrolytes. A mixture of trichloroacetic acid (TCA, pKa 5 20.5), dichloroacetic acid (DCA, pKa 5 1.1), and monochloroacetic acid (MCA, pKa 5 2.86) was separated by passage through a cation-exchange resin eluted with 0.01 M HCl. The order of elution was TCA , DCA , MCA. Explain why the three acids are separated and the order of elution.

In ion-exclusion chromatography, ions are separated from nonelectrolytes (uncharged molecules) by an ion-exchange column. Nonelectrolytes penetrate the stationary phase, whereas ions with charge of the same sign as that of the stationary phase are repelled by the stationary phase. Because electrolytes have access to less of the column volume, they are eluted before nonelectrolytes. A mixture of trichloroacetic acid (TCA, pKa 5 20.5), dichloroacetic acid (DCA, pKa 5 1.1), and monochloroacetic acid (MCA, pKa 5 2.86) was separated by passage through a cation-exchange resin eluted with 0.01 M HCl. The order of elution was TCA , DCA , MCA. Explain why the three acids are separated and the order of elution.

EBK A SMALL SCALE APPROACH TO ORGANIC L

4th Edition

ISBN:9781305446021

Author:Lampman

Publisher:Lampman

Chapter88: Column Chromatography

Section: Chapter Questions

Problem 5P

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