Chromatography: Principles, Types, and Applications in Science
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52 Terms
What is chromatography?
A technique used to separate a mixture into its individual components.
What are the three main purposes of chromatography?
Separation, identification, and quantification of mixture components.
What are the two phases in chromatography?
Stationary phase and mobile phase.
What is the stationary phase?
The phase that interacts with compounds and causes separation.
What is the mobile phase?
The phase that moves compounds through the stationary phase.
Why do compounds separate during chromatography?
They interact differently with the stationary phase.
What happens to compounds that interact strongly with the stationary phase?
They move more slowly.
What happens to compounds that interact weakly with the stationary phase?
They move more quickly.
Who invented chromatography?
Mihail Tsvet.
When did Tsvet invent chromatography?
1900.
What adsorbent did Tsvet use in his original experiment?
Calcium carbonate.
What pigments did Tsvet separate?
Chlorophylls and carotenoids.
When was the term "chromatography" first used?
1906.
What type of chromatography did Tsvet develop?
Adsorption column chromatography.
Why was Tsvet's work initially overlooked?
Political turmoil and language barriers.
How is chromatography used in food testing?
Detecting contaminants and additives.
How is chromatography used in forensic science?
Analyzing substances from crime scenes.
How is chromatography used in pharmaceuticals?
Purifying and analyzing drugs.
How is chromatography used in environmental analysis?
Monitoring pollutants in air, water, and soil.
What is the main purpose of column chromatography?
To purify compounds and separate mixtures.
Is column chromatography fast or slow?
Slow.
What is the stationary phase in column chromatography?
Silica gel (polar).
What is the mobile phase in column chromatography?
A mixture of polar and nonpolar solvents.
How does a polar compound behave in column chromatography?
It interacts strongly with silica and moves slowly.
How does a nonpolar compound behave in column chromatography?
It interacts weakly with silica and moves quickly.
What happens if the solvent is too polar?
Compounds move too quickly, causing poor separation.
What happens if the solvent is too nonpolar?
Compounds move very slowly or not at all.
What does TLC stand for?
Thin Layer Chromatography.
What is the stationary phase in TLC?
Silica gel (polar) coated on a glass plate.
What is the mobile phase in TLC?
A mixture of polar and nonpolar solvents.
What is TLC mainly used for?
Testing purity, identifying compounds, and monitoring reactions.
How can TLC determine purity?
Pure compounds usually produce one spot.
How can TLC identify the number of compounds in a mixture?
Each compound produces a separate spot.
How is TLC used with column chromatography?
To monitor separation and select the best solvent.
How far above the bottom of the plate is the baseline drawn?
1.5 cm.
What is the baseline?
The line where samples are spotted.
Why should TLC samples not be too concentrated?
They produce poor spots and inaccurate results.
What tool is used to spot samples on a TLC plate?
A capillary tube.
Where should the solvent level be relative to the baseline?
Below the baseline.
When should TLC development be stopped?
When the solvent front is about 1 cm from the top.
How can TLC spots be visualized?
UV light or iodine vapor.
What does Rf stand for?
Retardation Factor.
What is the formula for Rf?
Rf = (distance traveled by spot) / (distance traveled by solvent front).
What is the range of Rf values?
0 < Rf ≤ 1.
What does a larger Rf value indicate?
The compound traveled farther and interacted less with the stationary phase.
What does a smaller Rf value indicate?
The compound traveled less and interacted more strongly with the stationary phase.
Can an Rf value be greater than 1?
No.
Which compounds generally have the lowest Rf values on silica gel TLC?
The most polar compounds.
Which compounds generally have the highest Rf values on silica gel TLC?
The least polar compounds.
Why is silica gel considered polar?
It contains many polar Si-OH groups that interact strongly with polar molecules.
In normal-phase TLC, which compounds move fastest?
Nonpolar compounds.
In normal-phase TLC, which compounds move slowest?
Polar compounds.