Below are two chromatograms using the exact same certified HPLC Column, with the exact same NIST traceable standards on the exact same day. The older HPLC instrument and the newer instrument may be plumbed differently. This is only an example of how two different instruments can produce very different results with these conditions.
Recommendation: Make sure all fittings are new, secure and all tubing is well cut and is as short as possible. Not all HPLC instruments offer optimal extra volume. Check with your instrument manufacturer on how to optimize your system.
Hint! Use the MicroSolv PQ Kit for determining system extra column volume before transferring methods to different instruments, departments or clients.