Which factors can increase the retention time

A longer retention time may be caused by back pressure developing during analysis. The following factors may increase the retention time of analyte (drug molecule):

  •     Pump has not been cleaned satisfactorily
  •     Unfiltered buffer used
  •     High buffer capacity was used with solvent (methanol and/or acetonitrile)
  •     Guard column blockage
  •     Unfiltered dissolution sample was injected


Retention time of the drug can be increased (right hand graph) if back pressure develops during HPLC sample analysis