Chromatography

Question 1

Chromatography Types

Answer 1

There are two types of chromatography, column and planar

Question 2

GLC (Definition)

Answer 2

Gas Liquid Chromatography is the partition of an analyte between a gaseous mobile phase and a liquid stationary phase that is IMMOBILISED on surface of an inert solid

Question 3

GLC (Diagram)

Answer 3

Draw Diagram on nearest piece of paper, compare with notes

Question 4

GLC (Gas Supply)

Answer 4

Gas needs to be inert, relate to the type of detector, nature of stationary phase, operation environment, cost of gas. Note that scrubbers are used to remove O2 or impurities from gas

Question 5

GLC (Injection System)

Answer 5

The injection needs to be rapid to avoid band spreading/poor res. Sample is a volatile solution, injector is in a hot block to volatise. Note that precision can be improved by using a robot (auto-sampler) or a sampling valve

Question 6

GLC (Column Oven)

Answer 6

Temperature Programming = High Res. and Dec. Analysis time

Question 7

GLC (General Elution Problem)

Answer 7

Separation increases as length of column increases however peak broadening also increases. Optimum resolution at lower temperatures but then elution time decreases = zone broadening

Question 8

GLC (Detector)

Answer 8

The detector TCD (Thermal Conductivity Detector) is used generally. It is simple, non-destructive. Works by measuring thermal conductivity of eluent

Question 9

LLC (Efficiency)

Answer 9

Increase efficiency by reducing plate height, therefore having more plates per unit length of stationary phase. To reduce plate height you reduce the size of particles in the stationary phase, however in doing this you need to pump mobile phase at higher pressure (HPLC)

Question 10

LLC (Pump)

Answer 10

Must be resistant to corrosion. By having two reciprocating pumps, you can have a smooth flow without pulsing (which affects reproducibility)

Question 11

LLC (Injector)

Answer 11

Introduces sample to mobile phase (NO BUBBLES ALLOWED). Injector can be automated (auto-sampler like GLC)

Question 12

LLC (UV Detector)

Answer 12

Requires analyte to have chromophore, detector has a dual wavelength, and has multi wavelength detectors

Question 13

LLC (Definition)

Answer 13

Liquid-Liquid Chromatography is a type of partition chromatography where the liquid phase is coated on solid support. The chromatography occurs in a column which withstands high pressures and is packed with a stationary phase (silica)

Question 14

HPLC (LLP)

Answer 14

Liquid-Liquid Partition

Question 15

HPLC (LBP)

Answer 15

Liquid-Bonded Phase Partition

Question 16

HPLC (LL vs LB)

Answer 16

Liquid-Liquid: Stationary phase held by physical absorption onto solid support
Liquid-Bonded: Stationary phase covalently bonded to solid support

Question 17

HPLC (Normal/Reverse)

Answer 17

Normal - Polar Stationary/Non-Polar Mobile

Reverse - Non-Polar Stationary/Polar Mobile

Question 18

HPLC (Applications)

Answer 18

Forensics, Pharmaceuticals, Clinical medicine

Question 19

Chromatography Definition

Answer 19

Chromatography is the separation of two or more substances by virtue of their different affinities towards a stationary phase and a mobile phase that moves in relation to the stationary phase