Sometimes when my original method contains a gradient there is a mismatch between the number of steps in my “Original” and “Translation” methods. Why does this happen and when should I expect it to happen?

This occurs because of a significant change to either column diameter or dwell volume (e.g., when transferring a method from one LC system to another LC system). In some instances, these differences can effectively act as a hold time at the initial %B. Depending on the scenario, an isocratic hold may be needed or not needed in the translated method for equivalence.

• Scenarios when an initial isocratic hold will be added to the translated method:
  • The dwell volume of the original method is greater than the dwell volume of the translated method.
  • Going from a narrow bore (ID) column to a wide bore (ID) column.
  • Going from a shorter (length) column to a longer (length) column with the ID of the columns changing.
  • Any combination of the above.
• Scenarios when an initial isocratic hold is not needed in the translated method:
  • The dwell volume of the translated method is greater than the dwell volume of the original method.
  • Going from a wide bore (ID) column to a narrow bore (ID) column.
  • Going from a long (length) column to a shorter (length) column with the ID of the columns changing.
  • Any combination of the above.