Chromatography Forum

You are correct that the column should extend barely out of the transfer line itself--not out of the ceramic/spring interface tip.

Are you running in SIM or scan? Have you noticed any ions associated with column bleed? Have you tried a new column?

Also, do try re-printing tune reports after a few runs to see if your abundances are consistent.

Thanks aldehyde, I've been running tunes every time I change something or run stds.

one of colleague was thinking of switching the source to EI and running a leak test... he said that sometimes the CI source gives you false positives. Also, it'll be a way to see if maybe the source is du for retirement.

update... a co-worker suggested I switch ti EI and do a leak test in EI mode... so I changed the source and surprise surprise, water and air was really high. So gave everything a little extra snug let it bake overnight and this morning all's good.

Venting now and will re-install the CI source. I'll update once all's done.

I should have studied arts

FINALLY!! I reinstalled the CI source, pumped down, let stabilize for 2hrs+... loaded PCINH4 tune file then ran methane pretune-all good, laoded NCINH4 tune file then ran CI autotune-results all good. Ran a 1st injection of my std... great results, ran a 2nd injection of the same std... still great and a match to the 1st... running a third one as we speak and it seems good so far.

So the moral of this story... do not trust PCI mode when checking for leaks... results can be and were for me, false "ok". Best bet, if you have a an EI source handy... install do leak test then swap.

Thanks eveyryone for your feedback and help... greatly appreciated.

cheers

You can also set up to run EI with the CI source in, and then do a blank run in scan with a range of like 10-300 to check for background air/water/n2/garbage. Glad to hear everything is working.

I have the system I'm working on looking better than it has in 3 years (looking at their data).....except sensitivity still dies after like 10 runs, ugh, attacking the problem from a different angle though so maybe I can make some progress .