Question

1. Describe stationary phases and strong versus weak mobile phases for Reverse-phase chromatography, Hypophilic Imteraction chromatography, and Ion Exchange chromatography.

2. Describe commonly used ion exchange materials and elution modes.

3. Describe “ion-exchange,” “ion-pair,” and “ion” chromatography.

Please try to answer ALL questions, thank you!!!!

Answer 1

Reverse phase chromatography - Molecules that possess some degree of hydrophobic character, such as proteins, peptides andnucleic acids, can be separated by reversed phase chromatography

Stationary phase- Hydrophobic solid support, consists of hydrophobic ligands chemically grafted to a porous, insoluble beaded matrix. The matrix must be both chemically and mechanically stable. Generally composed of silica or polystyrene. Linear hydrocarbon chains (n-alkyl groups) are the most popular ligands used in reversed phase applications.

Mobile phase- Decreasing the mobile phase polarity by adding more organic solvent reduces the hydrophobic interaction between the solute and the solid support resulting in de-sorption. Usually contain strong acids at low pH with large concentrations of organic solvents.

The more hydrophobic the molecule the more time it will spend on the solid support and the higher the concentration of organic solvent that is required to promote de-sorption.

Hydrophilic Interaction Chromatography - Valuable alternative to reversed-phase liquid chromatography separations of polar, weakly acidic or basic samples.

Stationary phase- Silica gel with decreased surface concentration of silanol groups, or with chemically bonded amino-, amido-, cyano-, carbamate-, diol-, polyol-, or zwitterionic sulfobetaine ligands are used as the stationary phases.

Mobile phase- Aqueous-organic mobile phases rich in organic solvents

Ion Exchange chromatography- In cation exchange chromatography positively charged molecules are attracted to a negatively charged solid support. Conversely, in anion exchange chromatography, negatively charged molecules are attracted to a positively charged solid support.

Stationary phase- The stationary phase surface displays ionic functional groups (R-X) that interact with analyte ions of opposite charge.

Mobile phase- proteins are eluted by increasing the ionic strength (salt concentration) of the buffer or, occasionally, by changing the pH . As ionic strength increases, the salt ions (typically Na+or Cl-) compete with the bound components for charges on the surface of the medium and one or more of the boundspecies begin to elute and move down the column.