pressure spike in random injections

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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Instrument: Perkin Elmer Altus

I seem to be getting a random pressure spike in random injections - to me I think it looks like it could be air. I don't get this if I am just running mobile phase, it only happens if I do an injection and it's not every injection.

Furthermore, just last week or so the instrument ran perfectly fine, I just noticed it when I ran a sequence this past Thursday and again yesterday. I don't see any air bubbles in the syringe when the system injects, so...

I am just here to get some more ideas as to where I might look. Do I need to do a more thorough cleaning and purging of the syringe and loop? Here's a chromatogram of the pressure spike and what I am getting on my detector response when it happens. I was fortunate enough that it didn't overlap with any of my actives, or appear close enough to influence the results.


It looks like your rotor seal needs some maintenance.
Good luck.
Gerhard Kratz,
That up/down deflection is a normal injection Peak and is caused by the pressure change inside the system when the injection valve changes from the load to the inject position. Its size will vary depending on the volume injected (which effect the TIME), the detector and settings used to observed it, the noise level of your baseline, and the viscosity of the liquid injected. It would not appear if no injection was made. It is normal. Have you had any formal training in HPLC ? Might want to read up on it or get some local help using the system.
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