SELECTIONGUIDE
RestekCapillaryGCColumnSelectionGuide
Column Length
Longer columns providemore resolving power, but increase analysis time and column purchase
costs. As you consider whether the increase in resolution is worth the extra time and expense,
remember that the benefit of using a longer column ismuch greater if you are performing a
temperature programmed analysis than if you are performing an isothermal analysis. In an
retention time varies directlywith column length: if column length is
doubled, analysis timewill double as well. The increase in resolutionwill be only approximately
40%, however, because resolution is related to the square root of column length, as shown in
the equation below. In a
retention times aremore
dependent on temperature than on column length. As column length is increased, the increase
in resolutionwill be the same as for an isothermal analysis, but therewill be only amarginal
increase in analysis time.
