Chromatography Forum

I have a Shimadzu LC2030 with PDA detector. I analyze at 200 nm using a gradient of water and acetonitrile and a new Agilent Zorbax Eclipse XDB-C18 4.6 x 150 mm, 5um pore at 40C. My guard column has less than 10 runs on it. My co-worker is using an equivalent system and can mostly separate these pesticide peaks between 2-3 minutes elution time - but his are much sharper peaks! The starting eluent is basically 30% acetonitrile in water.

I would love to share a jpg - but don't know how to put it here.

Can anyone explain why my peaks are so dull and not sharp at all for my peaks of interest?

So it's a gradient analysis on two different systems - so I'm not surprised the chromatography is different.

Could be different system volumes, different dead volumes, different way of mixing the solvents, etc.

I would love to share a jpg - but don't know how to put it here.

Set up a free account at Imgur.com, upload there, then copy the code (Ctrl C) and paste in this window (Ctrl V).

Agreed - you should establish the dwell volume of your system and compare to that of the other system.
Some Shimadzus have pretty high dwell volumes, especially their older modular systems (by default).
If that is not the issue, it could be that there's a gap in a union somewhere between the injector and detector.
If you're using a fatter version of an otherwise identical column, that could also broaden your peaks compared to the other system.

Hi LabPro,
Building off what others have said so far, if we could get some more information regarding this "equivalent system" then it would be easier to diagnosis some potential differences that result in your peak/band broadening. Additionally, I assume the columns are exactly the same, but if they aren't then that could certainly change the resolution and sharpness of your peaks. Disregarding the system, how do the two methods compare? Are they identical methods on two different systems, or potentially two different methods where one is trying to mimic the separation on the other system? Please provide some more details and we'll be able to narrow-down where some of your band broadening exists.