2D chromatography

Question 1

What does ortogonal selectivity mean?

Answer 1

It means it requires two opposite retention modes

Question 2

Why is it beneficial to use two dimensions?

Answer 2

-Greatly increased peak capacity
* Improved resolution due to increased selectivity without greatly
increasing analysis time
-A single gradient can be
inadequate for the
separation of complex
samples

Question 3

Do we want the first dimension to be really slow or really fast?

Answer 3

Really slow. And second dimension really fast.

Question 4

What does Orthogonality mean?

Answer 4

– retention times in the 1st dimension independent of the retention
times in the 2nd dimension
– different separation modes is required

Question 5

What are examples of using two different modes?
Why can’t we use normal phase and reversed phase together?

Answer 5

• HILIC x RPLC; HILIC in 1D due to slow re-equilibration
• IEC x RPLC
• SEC x RPLC

Because that would require two different (and opposite) stationary phases

Question 6

What is RPLC?

Answer 6

reversed phase liquid chromatography

Question 7

Give an example of a mode setup that works well

Answer 7

IEC x RPLC
» IEC: Aqueous solution of increased ionic strength
» RP: 10% to 90% acetonitrile in water