several questions from a total greenhorn

[mischka80]

hi

I´m an undergrad student doing a practical internship
5 weeks ago I had never ever dealt with a GC, not to speak about fixing problems...

when I can see clearly the peaks, but the integrator does not integrate it, is one possibility (among others!)of the problem a wrongly set Peak Witdh?
does changing the peak witdh influence the calculating? I mean do I need to make a new calibration after I changed this parameter?

when I plot the sensitivity against the detector current, does the graph pass through a maximum or is it all the way increasing until the filament burns out?

and I think my GC (Gow Mac 550 Series) has some kind of slacky joint or the like... without any warning the baseline becomes a straight line without any noise
running with sample gases I only get idle peaks
the peaks are in the right place, but sometimes they even go in the wrong direction
when I switch the polarity then the plot looks like normal, just upsidedown of course
do you have any idea what it could be

I´m lost...

thx
Michael

[mischka80]

you probably need some more info

it deals about detecting H2, CO and CO2 in He carrier gas flow
I use a TCD detector and a HP 3396 integrator

H2 detection is tricky, range 0...20%

[Radish]

Michael,

I'm sorry I am not familiar with your instrument, but in general, peak width, slope sensitivity, and area reject are all things that may need adjusted in your integration parameters. Also a calibrated peak may not be identified properly if it is outside the retention time window of your standards. Ideally when you correct your integration problems you should re-calibrate, or re-integrate stored calibration runs with your new integration parameters.

[chromatographer1]

mischka80

You should not try to measure Hydrogen in Helium at levels 5-10% The response of hydrogen changes and it behaves non-linearly.

Use Nitrogen (or Argon) carrier to measure hydrogen.

best wishes,

Rodney George
rgeorge@sial.com

[chromatographer1]

mischka80

Sorry I forgot to add it appears that your TCD is not balanced. You have the flow through the reference at a level too high or low compared to the measurement cell. Try to find the manual for the detector and look at the examples for troubleshooting.