Chemistry A2 · Analytical techniques. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
In gas/liquid chromatography the sample is injected, turned to vapour and carried through a long heated column by an unreactive gas such as nitrogen or helium. This carrier gas is the mobile phase. The stationary phase is a non-polar liquid of high boiling point, held on a solid support inside the column.
Each component spends part of its time dissolved in the liquid and part in the gas. A component that is more strongly attracted to the stationary phase stays in the column longer.
The retention time is the time from injection until the component reaches the detector. The area under each peak shows how much of that component is present.
Students use peak heights to find the percentage composition. The amount is shown by the area under the peak, so a short, wide peak can represent more substance than a tall, narrow one.
Answer: P is 25% and Q is 75% of the mixture
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