What to do if the retention time of a drug is reduced during HPLC analysis

A shorter retention time is caused by the drug molecule interacting less with the stationary phase. This may occur if an undiluted biorelevant drug sample is injected into an HPLC or the dilution is insufficient. If the variation (relative standard deviation) is greater than your inhouse limit and still occurs after sample dilution, a guard column can help with this issue.


Retention time of the drug can be reduced (right hand graph) if biorelevant drug samples are injected undiluted

If the chromatographic properties change substantially during a sequence, a washing cycle can be introduced.