Relative Retention

Since absolute retention times are affected by many operation parameters, retention parameters less dependent on column dimension and analysis conditions may be desired. Such parameters are expressed by the relative relation of adjustable retention time between the standard sample and unknown sample: relative retention and retention index.
The advantageous point of relative retention is that it depends only on the ratio of distribution coefficients, and the effects from some parameters, such as column length and carrier gas flow, are basically cancelled out.
However, there are some limitations for relative retention. Measurement errors will increase for target peaks located far from reference peak and it is hard to find a relation with a chemical structure.