Question

In Preparative Gas Chromatography with a mixture, 3-pentanol was found to have a starting collection time of 3.81 minutes and an ending collection time of 5.38 min. What is its retention time? Which compounds have higher/lower retention times, and what are some factors that affect retention time?

Answer 1

Retention time is the time taken by the component to pass through the chromatography column. It is the time from the injection of sample into the chromatographic column to the elution of the component. It is usually measured in seconds or minutes.

Each component have different retention time based on interaction with stationary phase inside the chromatography column.

Retention time for 3-Pentanol= (5.38minutes) - (3.81 minutes)= 1.57 minutes

• Retention time is based on the strength of interaction of the component with the stationary phase. The more stronger the interaction of component with stationary phase, more time will be taken by the component to migrate through the chromatography column which leads to longer retention time. If there is low interction of component with stationary phase then it takes less time to migrate through the column, which leads to shorter retention time.

Factors that affect retention time:

1. The rate gas flow inside the column
2. Column degradation
3. Column Length
4. Column temperature
5. Boilin point of component