Same interval peaks

[DocHollywood]

Hi,
I recently have been getting peaks eluting out at the same interval, even when i don't inject anything into my Plot U capillary column on my 5890 series 2 GC. There is basically an array of them which can small peak heights coming out at around every 40-50 seconds. Has anyone seen something like this before? If so, some direction would be useful before i start to take the GC apart.
Thanks
AD

[Peter Apps]

Please post an example - instructions are in a sticky at the top of the LC page.

Peter

[DocHollywood]

Here is the image
Don't mind the fact the base line goes down initially that just occured on the run i saved because i had changed the pressure of hydrogen to the Mass Flow Controller. You can see the peaks come at regular intervals.


Thank you for your time

[Peter Apps]

This looks like electrical interference. Check around for any equipment that switches on and off at these intervals.

Peter

[larkl]

If you change the temp gradient or the temperature (if it's isothermal), then you could tell if the peaks move. If they do, wouldn't it be some contamination? If they don't, then it's electronic.

[DocHollywood]

Thanks for the quick response