Varying retention times: Causes and Solutions

                          Possible Cause                                                Solution
 
 

Gradient - insufficient column-regeneration time     Ion pairing - insufficient equilibration time     Isocratic - insufficient equilibration time

Increase equilibrating time in mobile-phase A to obtain constant retention times for early peaks Increase equilibration time; ion pairing may require as much as 50 column volumes for mobile-phase changeover Pass 10-15 column volumes of mobile phase through column for equilibration