Question about gas chromatography - O Chem.. The retention time for cyclohexane

Question

Question about gas chromatography - O Chem..

The retention time for cyclohexane on a gas chromatography instrument is 0.75 minutes. The temperature of the gas chromatography column is 70 degrees C and the gas flow rate is 60 mL/minute.

A.) Would the retention time be higher or lower if the column temperature is raised to 100 degrees C?

B.) Would the retention time be higher or lower if the flow rate is changed to 30 mL/minute?

C.) Would the retention time be higher or lower if the column length was decreased to 1/2 the length?

Explanation / Answer

A.) Would the retention time be higher or lower if the column temperature is raised to 100 degrees C?

Retention time will lower, because increase in column temperature will facilitate fast equilibrium and will leads to fast elution of the peaks

B.) Would the retention time be higher or lower if the flow rate is changed to 30 mL/minute?

Retention time will be higher, because of decreasing in flow of gas will leads to less interaction of sample with carrier gas

C.) Would the retention time be higher or lower if the column length was decreased to 1/2 the length?

Retention time will be higher due to decrease in column length leads to less equilibrium

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