New column gives me different values from replaced column..

[Johnhz2000]

Hi all,

I am having trouble with getting repeatable values when changing out an old column to a new column (Waters symmetry 3.5 um, 4.6x150 mm). Is this something that is common? I compared values of a run using the replaced column vs. the new column and they are different approx by 7%. I need some suggestions as to why this is happening. Thanks.

[tom jupille]

A certain amount of column-to-column variability is normal. The other issue, of course, is that your old column may have changed in use. If you can go back and find chromatograms run when that column was new, you will be able to tell if column aging is the problem.

Unless you have a method with *very* tight system suitability specs for retention time, and so long as you are getting acceptable resolution on the new column, I wouldn't worry about it.

[HW Mueller]

What is changing 7%?

[Johnhz2000]

The HPLC area of a certain peak has changed by about 7% from an old column to a new column. Both old and new column give the same resolution for this critical pair peaks (resolution is approx. 1.1 and retention times differ by about half a minute or so), but have different numbers. Thanks.

[HPLCaddict]

Resolution of 1.1? The first thing I'd try is to improve resolution
At 1.1, I suppose those peaks show a considerable overlap. Integration precision might be worse than 7% under these conditions