HPLC test

What happens to the given substance under reverse phase conditions when the pH of the mobile phase is raised?

• Retention time doesn't change

• Retention time will increase

• Retention time will decrease

Which of the following mobile phases would provide the strongest elution conditions in reversed phase chromatography?

• 50% water, 50% acetonitrile

• 50% water, 25% acetonitrile, 25% THF

• 100% acetonitrile

• 50% acetonitrile, 50% THF

What will happen with the retention time of the given molecule in reversed-phase HPLC if the water content of the mobile phase is increased?

• Increase

• Decrease

• Stay the same

Rank the solvents in order of increasing strength under HILIC conditions. Place the weakest solvent first and the strongest last.

• Water – Methanol – Acetonitrile – Isopropanol

• Water – Acetonitrile – Isopropanol – Methanol

• Water – Methanol – Acetonitrile – Isopropanol

• Acetonitrile – Isopropanol – Methanol – Water

What is the most commonly used stationary phase in reversed phase chromatography?

• C18

• Silicagel

• C8

• Carbon

In what order will these substances elute from the column in reverse-phase chromatography? Start with the least retained substance.

• C A D B

• A C D B

• B A C D

• C A B D

In what order will these substances elute from the column in reverse phase chromatography? Start with the least retained substance.

• C A B D

• B A C D

• C B A D

• A B D C

Which one is the binary pump?

• A

• B

The chromatograms shown were obtained with four different mobile phase systems (same sample, reverse phase conditions): 30% THF, 30% acetonitrile, 30% methanol, and 40% methanol.
Which chromatogram was obtained with 30% methanol?

• 1

• 2

• 3

• 4

What is the purpose of gradient elution in HPLC?

• To increase retention time

• To reduce resolution

• Improve the separation of complex mixtures

• To reduce the pressure drop in the column