What is retention time?

Retention time refers to the period of time that a substance or molecule spends in a chromatography column before being eluted. It is a characteristic of the specific compound and is influenced by various factors such as the chemical composition of the sample, the stationary phase of the column, the mobile phase, temperature, and pressure. The retention time is an important parameter in chromatography as it is used to determine the identity of a compound by comparing the retention time of the unknown compound with that of a known standard. In gas chromatography, for example, the retention time is measured in minutes and can be affected by changes in flow rate, column length, and temperature. In liquid chromatography, the retention time is typically measured in hours and can be affected by changes in solvent composition, pH, and ionic strength.