What is the purpose of chromatography in chemistry?
To separate and identify components of a mixture.
Different types of chromatography are chosen depending on the sample and stationary/mobile phases.
Name three common types of chromatography.
- Thin-layer chromatography
- Column chromatography
- Gas chromatography
TLC uses a plate, CC uses a packed column, GC uses a gas mobile phase with a column.
Fill in the blank:
In TLC, a plate is coated with a ______ and a solvent moves up the plate.
solid
The solid acts as the stationary phase while the solvent is the mobile phase.
True or False:
In column chromatography, the solvent moves down the column.
True
The stationary phase (solid) is packed in the column and components are separated by interaction with it.
What factor determines the separation of substances in chromatography?
Relative solubility and retention
Compounds with higher solubility in the mobile phase move faster; retention is determined by affinity for the stationary phase.
Fill in the blank:
The ratio used to quantify the movement of a spot in TLC is called the ______ value.
Rf
Rf = distance travelled by substance / distance travelled by solvent front.
True or False:
Retention time in gas chromatography can be compared with standards to identify substances.
True
Each compound has a characteristic retention time under specific conditions.
How can mass spectrometry be combined with gas chromatography?
To analyse separated components.
GC separates compounds and MS provides molecular weight and structural information.
Fill in the blank:
In TLC, the Rf value is always between ______ and 1.
0
Rf = 0 if the substance does not move and Rf = 1 if it moves with the solvent front.
What is the mobile phase in gas chromatography?
Gas
A carrier gas, such as helium or nitrogen, transports components through the column.
True or False:
Rf values and retention times are compared with standards to identify unknown substances.
True
This allows identification of compounds in mixtures.
What laboratory application uses TLC to identify analgesics or metal ions?
Test-tube separation and identification
TLC separates components for visualisation and comparison with known standards.
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3.1.1 Atomic structure50
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3.1.2 Amount of substance47
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3.1.3 Bonding90
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3.1.4 Energetics62
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3.1.5 Kinetics55
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3.1.6 Equilibria & Kc24
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3.1.7 Redox equations17
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3.1.8 Thermodynamics27
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3.1.9 Rate equations24
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3.1.10 Kp12
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3.1.11 Electrode potentials46
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3.1.12 Acids and bases69
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3.2.1 Periodicity22
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3.2.2 Group 2 metals24
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3.2.3 Group 7 (halogens)31
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3.2.4 Period 3 oxides35
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3.2.5 Transition metals95
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3.2.6 Ions in aqueous solution39
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3.3.1 Intro to organic chemistry42
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3.3.2 Alkanes49
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3.3.3 Halogenoalkanes36
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3.3.4 Alkenes36
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3.3.5 Alcohols43
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3.3.6 Organic analysis36
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3.3.7 Optical isomerism12
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3.3.8 Aldehydes & ketones20
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3.3.9 Carboxylic acids & derivatives25
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3.3.10 Aromatic chemistry29
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3.3.11 Amines41
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3.3.12 Polymers24
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3.3.13 Amino acids, proteins, DNA61
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3.3.14 Organic synthesis12
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3.3.15 NMR spectroscopy14
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3.3.16 Chromatography12
