Chromatography Forum

Hi all, hope someone can kindly advise me ~

I did passivation as per what was done earlier by a member here and I have narrowed down the ghost peaks to a problematic water source.

Using other source of ultra pure water from another lab, I managed to get neat blanks without any carry over peaks.

Our lab purchased a new UPW system recently from Millipore, and to my horror, the ghost peaks re-appeared again with the same intensity in every injection.

I was thinking that the water source in my lab was contaminated; but is it even possible that can happen with a new ultra pure water system?

Looking for some kind wisdom and help here.

Thanks a lot !

First, you need to understand the problem.
Carry over peak is a rest of a previous sample and is typically due to inadequate injector wash. The retention time of this kind of peaaks is the same as the Rt of a normal sample's peak.
Peaks due to poluted water or other mobile phase components appear in gradient elutions tipycally shortly after the gradient starts.
So you need to identify the source of the interfearing peak and then there will be a solution

If you need help we will need some more information about what you are experiancing.

Best Regards

I have had acrylonitrile appear in water from my Millipore A10 after the Q-pak was changed. I couldn't pinpoint the source though as it was sporadic and only in the blank water. It went away eventually.

Did you ever use online cleanig columns like the Ghost Buster (Welch), Ghost-Guard-LC (Analyte) or Ghost Trap DS (Shimadzu)? They are installed right behind the gradient pump and remove traces of impurities from the mobile phase.

Did you have a look at the Troubleshooting wizard here?

http://www.lcresources.com/resources/TSWiz/hs100.htm

also see the Diagnostic entry about "gradient garbage" to narrow down the source of the problem.
- test if peaks get bigger when equlilibrating longer
-> water as source.

also what about contaminated glaswares?
When doing the tests with the other (good) water source, where the glaswares the same as usual?

What about the feed water before the UPW system?
If it.s too highly contaminated then maybe the UPW can.t purify it enough?
If it comes from new filter parts of the UPW,
flush the new UPW for prolonged times and repeat test