Factors Affecting Retention Time in Gas Chromatography

GC is a powerful analytical technique for the separation of volatile compounds, whose analyte separation depends on the interaction strengths of each compound with the stationary phase. Each component is separated from the column with a specific retention time (RT), the retention time of a compound depends on several factors such as the conditions of the analysis, the temperature and the type of column used, the dimensions of column and degradation column. sample etc... Some factors which affect the retention time in GC are mentioned here.

Component volatility:
Compared to non-volatile components, the volatile component moves rapidly through the GC column. Volatility is related to the size and boiling point of molecules. This means that smaller molecules have a short RT compared to larger molecules.

Component polarity:
The polarity of compounds is associated with the polarity of the stationary phase. When the stationary phase and the polarity of the compost are parallel, the RT increases. This happens when the compound has more interaction with a stationary phase.

Quantity of sample injected:
The amount of sample does not affect the retention time. If the sample is injected in large quantity, the peak presents a more than asymmetrical tail shape.

Amount of stationary phase:
The retention factor (k-value) of analytes is associated with the amount of stationary phase. If the most stationary phase exists, the retention factor is higher and hence the retention time will be longer.

Column length:
A longer column generally increases retention times and also improves separation.

Column temperature:
The high temperature of the GC column is the result of low retention time with poor separation.

Carrier gas flow and types:
Hydrogen gas offers a short analysis time, compared to other carrier gases (helium) used in gas chromatography. High flow can also reduce component retention time.