Ion Exchange Chromatography

Question 1

What is IEC?

Answer 1

retention is based on electrostatic interaction between solute ions and fixed ion charge on the stationary phase
cations need cation exchanger
anions need anion exchanger

Question 2

Backbone for SP

Answer 2

polystyrene/divinylbenzene
polymethacrylate
polyalcohol
hydroxyethylmethacrylate (HEMA)

silicate

Question 3

What mobile phase characteristics should be considered?

Answer 3

pH and it will affect the exchange groups of the SP

Question 4

Heavy crosslink resin have _____ IE sites and tr ______

Answer 4

more, increases

Question 5

Heavy crosslinking leads to ___________

Answer 5

slow equilibration of solutes. tr and N increase

Question 6

What is the pH range for silica based columns?

Answer 6

2

Question 7

What is the pH range for pH stable columns?

Answer 7

1

Question 8

What is ion capacity?

Answer 8

the number of functional groups per unit weight of the stationary phase

Question 9

K describes the relative selectivity of resin for + and - ions. Greater the K value ______________

Answer 9

means forward reactions is more favorable

selectivity of one of the ions for exchange resin is higher

Question 10

The larger the radius of the ions ____________

Answer 10

the smaller the solvent shell

Question 11

The larger the solvent shell _________

Answer 11

the less access the ion will have the exchange groups which will result in less retention and lower selectivity

Question 12

Increasing the percentage of crosslinking of the resin usually ________ the retention on polymer based columns

Answer 12

increases

Question 13

Why is the concentration outside the resin higher than inside the resin? (for similar charged ion/resin)

Answer 13

since the ions have the same charge, electrostatic repulsion will decrease the concentration inside the resin

Question 14

Advantages of silica based exchanger

Answer 14

lower capacity
N is better
do not swell with organic solvents

Question 15

Disadvantages of silica-based

Answer 15

peak tailing due to unreacted silanols

limited pH range

Question 16

The retention of solute ions will _______ if the concentration of counter ions is increased with the MP.

Answer 16

decrease

Question 17

Ions of ______ acids (phenols) or bases (aniline) may lose charge and are retained _______ on ion-exchange columns.

Answer 17

weak, less

Question 18

___________the charge of the solute ions increases its affinity for the IE sites on the column.

Answer 18

increasing, Pu4+ > La3+ (decreasing retention order)

Question 19

Ions with the ________ degree of solvation exhibit greater binding affinity and are retained less.

Answer 19

greater,

Cs+ > Rb+ > K+ > Na+ > Li+

Question 20

Attraction between induced dipole and the nearby resin charge ______ the binding for the ion.

Answer 20

increase

Question 21

Increasing the ion-exchange capacity ______ the retention, but selectivity ________.

Answer 21

increases, remains constant