Chapter 1 - Introduction

Question 1

What is liquid chromatography?

Answer 1

a physical separation technique conducted between two phases - a solid phase and a liquid phase.

Question 2

Chromatography meaning

Answer 2

“color writing”

Question 3

HPLC advantages

Answer 3

• Applicable to diverse analytes
• Precise and highly reproducible quantitative analysis
• HPLC coupled with MS
  
  • High separation power with sensitive detection

Question 4

HPLC perceived limitations

Answer 4

• Lack of an ideal universal detector
• Less separation efficiency than capillary gas chromatography
  
  • Still arduous for regulatory or quality control testing

Question 5

HPLC is amenable to _____ % of all existing compounds.

Answer 5

60 to 80

Question 6

GC is amenable for ______ % of all existing compounds.

Answer 6

15

Question 7

Primary separation modes of HPLC

Answer 7

1. Normal-Phase Chromatography (NPC)
2. Reversed-Phase Chromatography (RPC)
3. Ion-Exchange Chromatography (IEC)
4. Size-Exclusion Chromatography (SEC)

Question 8

NPC is particularly useful for the separation of

Answer 8

nonpolar compounds and isomers.

Question 9

NPC uses a _______ stationary phase and a _______ mobile phase.

Answer 9

polar; nonpolar

Question 10

One significant disadvantage of NPC is

Answer 10

easy contamination of the polar surfaces by highly retained sample components.

Question 11

NPC is primarily used in

Answer 11

chiral separations and preparative applications.

Question 12

RPC uses a ______ stationary phase and a ______ mobile phase.

Answer 12

nonpolar; polar

Question 13

In RPC, polar analytes elute

Answer 13

first.

Question 14

RPC typically uses a mixture of

Answer 14

methanol or acetonitrile with water.

Question 15

The mechanism of separation in RPC is mainly attributed to

Answer 15

hydrophobic interaction.

Question 16

RPC is used in approximately what percent of all HPLC analyses?

Answer 16

70%

Question 17

In ion-exchange chromatography, the separation mode is based on

Answer 17

the exchange of ionic analytes with the counter ions of the ionic groups attached to the solid support.

Question 18

In IEC, to force the migration of analytes, mobile phases consist of

Answer 18

buffers, often with increasing ionic strength (e.g. a higher concentration of NaCl)

Question 19

Size-exclusion chromatography is based solely on

Answer 19

the analyte’s molecular size.

Question 20

The goal of most HPLC analysis is to

Answer 20

separate analytes from other components in the sample for accurate quantitation.

Question 21

Baseline resolution is usually not needed for MS detection since

Answer 21

specific signals can be customized for each ion according to its molecular weight.