we have a GC-MS with a DB-HeavyWax Column. Yesterday we changed the column for a new one (the same). The retention times of our samples shifted 8-11 min. Now, the peaks appear 8-11 min later. We are using a flow of 1.8 mL/min, if we try to do a retention lock, the pressure would be so high. The new column is the same model as the old one. We don't understand why we have this change in the RT's. Column : 123-7132.