Chromatography Forum

Dear users!

I'm a "newbie" with chromatography, and i've had the very first big issue that i can't fix right now. Because of this, i would like to ask for some advice from experienced users.
Well, my problem is that since the new coloumn installation, the response from any samples (standard, sample etc.) is too much for the detector, causing flat topped peaks, unquantificable results. I switched the input to range 10, what caused quantable peaks, but the linearity and stability isn't perfect (and I was still slightly worded). There are two coloumns registered, one is the front ("the bad") and the other is middle for confirmation analysis. The main issue is that my "quantification" line is so bad, that i haven't been sure if the values are correct, since the coloumn installation. (before it, everything was right). I've read somewhere that my ECD cell may contaminated, and that is why i cant get normal chromatogram. (The coloumn installation was not correct either, because we weren't capped the ECD inlet)
Other issue: I have ghost peaks from previous sample runs (standard peaks overbleeding to the next runs), but it is only occuring on the FRONT coloumn, the middle isnt bleeding like this.
If anyone have some advice, or could help with telling same solved problem experiences, would be super.

Thanks!

Hi,
What ECD cell current are you using? Adjusting this can help find the optimum linear and dynamic ranges of responses. When you changed the column, did the column settings need changing on the GC or was it a like for like column?

For the ghost peaks, try running a few samples of ethyl acetate to flush the column. If they don't go then id recommend baking the column at a high temperature and even trimming the inlet end of the column to remove contamination.

You may have a leak. Ghost beaks usually stem from the injector.
If I were you I would revisit the column installation.

Dear repliers!

Thanks for the advices!

First replier:
It's running in CAP mode for capillary coloumn, and i have a few variables besides this, maybe i will try it but it have never been changed for like 10 years (so for the time we got this instrument). We have baked out the detector for thermally clean it, this method especially for varian GCs, i've read on a forum. On 395 C i baked, and also the got the coloumn re-conditioned on 300 C. The result was : got the response factor halved, but still cant measure on range 1, because the baseline is out of calibration, what is strange because that would be logical if the peaks, and signal be halved too.

second replier:
It's not the basic "ghost peaks" it is a "memory effect" what is like a standard peak of mine for example could be detected in the next 5 runs. But it minimalized by elonged the run times, and diluted the standards by half.

The main goal for me is to measure on range 1, like we did this before

Hello,

I hope the problem you had has resolved.

I am reaching out from Scion instruments - manufacturers of next generation of the CP3800 Varian system that you have.

Scion bought the IP for the Varian GC business, and are now manufacturing the next generations of the Varian systems in our Goes facilities.

We have also developed the Galaxie software into its new form - now called Compass CDS. This software works seamlessly with old data files and methods. S

Please reach out to me directly for any technical support/ hardware or upgrade support which may be required - on new or legacy Varain Gc Systems.

And this goes for anyone who has a Varian GC and is looking for parts/ software upgrade/ hardare upgarde/ just tech support. Please reach out.

Find me on linkedin: https://www.linkedin.com/in/sunny-s-852550a0/
Email: sunny.singh@scioninstruments.com

Hello,

I hope the problem you had has resolved.

I am reaching out from Scion instruments - manufacturers of next generation of the CP3800 Varian system that you have.

Scion bought the IP for the Varian GC business, and are now manufacturing the next generations of the Varian systems in our Goes facilities.

We have also developed the Galaxie software into its new form - now called Compass CDS. This software works seamlessly with old data files and methods. S

Please reach out to me directly for any technical support/ hardware or upgrade support which may be required - on new or legacy Varain Gc Systems.

And this goes for anyone who has a Varian GC and is looking for parts/ software upgrade/ hardare upgarde/ just tech support. Please reach out.

Find me on linkedin: https://www.linkedin.com/in/sunny-s-852550a0/
Email: sunny.singh@scioninstruments.com

Then i would grab the chance to take some questions about this problem.

The actual condition of this detector is not so well rigth now. About two month ago i managed to analyze on range 1 detector level, with a special split ratio, and this went on the following month, but now the response got from the detecor is high again. There are no measuring sequence without fail, or restart the equipment. The failure is when the chromatogram baseline goes up where the equipment cannot measure, and this is because of the high sensitivity.
The question is, is it possible in the galaxie software to "turn the detector on" about one , or two minutes into a measuring? Because, about 1,5 min there is a big negative peak what is the hexane. If i can got rid of it i could win measuring area on the y axis. Because the max. available measuring area on the y axis is 1000000 counts (or uV).
second question, I have read some cleaning method about varian GCs, and i've already tested one on my GC-ECD. This was the thermal cleaning. With that i got smaller peaks, but this was just temporary. There are some other cleaning methods like hydrogen cleaning (inject H2O on the coloumn), but i'm afraid of it, because this is our only ECD detector, and i do not want to cause harm on it.
Is there any other safe cleaning methods, do u know?

Thanks for the answer

Please email at sunny.singh@scioninstruments.com; this will help us get the right technical support to you based on your location. Kindest regards, Sunny

heykiwi89,

You really should not get a peak at all with hexane and an ECD. A baseline ripple but not much more than that. Considering the last thing you did was change columns, I would suggest two things. 1) plug the front end of the column with a septum and see if the zero drops. If it does not, suggests you might have a leak at the detector. If it does, it may be a carrier gas issue or a leaky inlet.

2) re-visit the distance the column is installed. The negative peak suggests you may have the column in the wrong zone in the detector.

Best regards,

AICMM