Chromatography (Lecture 12)

Question 1

What is the mobile phase?

Answer 1

solvent moving through the column, can be either liquid or gas

Question 2

What is the stationary phase?

Answer 2

It stays in place inside the column, is most commonly a viscous liquid chemically bonded to the inside of the column or to solid particles, or solid particles themselves can be the stationary phase

Question 3

What is the eluent?

Answer 3

the fluid entering the column

Question 4

What is the eluate?

Answer 4

the fluid exiting the column

Question 5

What is elution?

Answer 5

the process of passing the gas or liquid mobile phase through the chromatography column

Question 6

What is absorption chromatography?

Answer 6

It is where the solute is adsorbed onto a solid surface. The solid surface is the stationary phase and the mobile phase is the liquid solute. Can be used to test urine for drugs.

Question 7

What is partition chromatography?

Answer 7

It occurs within a column or on paper where the solute is dissolved in a liquid mobile phase which bonds to the surface of the column which acts as the stationary phase. It can be used for the separation and identification of amino acids (specifically the type with paper).

Question 8

What is ion-exchange chromatography?

Answer 8

It is where molecules of the liquid mobile phase pass through a solid stationary phase resin. If the molecule and the resin are oppositely charged, the molecule will attach itself to the resin. It can be used to analyse drinking water for pollutants.

Question 9

What is molecular exclusion chromatography?

Answer 9

It is also called size exclusion chromatography. It is different from the other types as there is no interaction between the liquid mobile phase and the stationary phase. It works as smaller molecules get caught in the stationary phase (solid silica beads) and have longer retention times but large molecules will pass straight through. This has been used for analysing protein biotheraputics.

Question 10

What is affinity chromatography?

Answer 10

It involves enzymes and their substrates. Molecules of the analyte that are substrates of the enzyme will bond to the enzyme and the other molecules will pass through. The stationary phase consists of solid beads which enzymes are bonded to. The mobile phase is liquid. It can be used for the purification and concentration of an enzyme solution.

Question 11

What is a chromatograph?

Answer 11

a graph showing the detector response as a function of elution time

Question 12

What equations are associated with chromatographs?

Answer 12

the equation for adjusted retention time = t’(r) = t(r) - t(m)
the equation for separation factor = 𝛼 = [t’(r₂)]/[t’(r₁)] = k₂/k₁
the equation for retention factor = k = (t(r) - t(m)) / t(m)

Question 13

Which equations can be used to calculate retention time at the partition coefficient?

Answer 13

Retention factor = k = (t(r) - t(m)) / t(m)
k = (time solute spends in stationary phase)/(time solute spends in mobile phase) = (moles of solute in stationary phase)/(moles of solute in mobile phase)
k = [c(s) x v(s)] / [c(m) x v(m)]

Question 14

Which equations can be used to calculate retention time at the partition coefficient (at eqm)?

Answer 14

K(D) = c(s) / c(m)
k= K(D) x [V(s) / V(m)] = (t(r) - t(m)) / t(m) = t'(r) / t(m)
𝛼 = [t'(r₂)]/[t'(r₁)] = k₂/k₁ = K(D₁) / K(D₂)

Question 15

The greater the ratio of partition coefficients between mobile and stationary phases…

Answer 15

the greater the separation between two components of a mixture

Question 16

What is retention volume?

Answer 16

the volume of mobile phase required to elute a particular solute from the column
V(r) = t(r) x u(v)
u(v) is the volume flow rate (volume per unit time) of the mobile phase