response vs. column age

[The Chemist]

we are seeing higher response for a particular compound (low level 0.3 ug/ml) on brand new column. As the column is getting older the response drops to about half, but the peak shape remains pretty much the same - nice symmetrical

anybody any thoughts as to what might be going on?

thanks

[tom jupille]

Some questions:

• Are you measuring peak area or peak height?
  By "response", do you mean the slope of the calibration curve (the "response factor") or are you referring to the size of the peak at a single level?
  Is the plate count staying constant? If not, how much is it changing?
  Any change in column pressure?
  Any change in retention time?
  Has the decrease in response been gradual, or did it occur abruptly?

[Gerhard Kratz]

In addition to Tom my questions are:
- what do you mean with old - 1 day, one week, one month?
- how often you use a fresh standard
- do you see any degradation product?
- UV detection?