I am using 'Y' splitter for our GCMS, it connected tat column outlet and one part is going to MS and another is going to FID; i have a sensitivity problem in FID and RT differences ( TIC-MS is 0.5 min earlier than FID).
how could i fix the RT problem and sensitivity issue; column used BP1 60m x 0.25mm, 0.25 u.
As the MS is under vacuum most of the sample is going to MS; so FID is giving less intense peak
Many Thanks
Hi Senthamizh!
I dont have experience with GC-MS systems, only with GC-irMS :-)
Basically you can increase the length of the capillay between splitter and MS, that should affect the RT at the MS.
The amount flowing to the MS might be reduced by additionly decrease the inner diameter of the capillary. What kind of capillary you are using (uncoated FS? Inner diameter?). If your are using already the smallest available diameter you might fit a metal capillary somewhere between splitter and MS which can be crimped. This kind of capillary is used at the dual inlet of an isotope mass spec.
Regards
Stefan
Dear Stefan,
you are absolutely right. i am using 170 cm capillary to FID, 240 cm to MSD as recommended by the Y splitter manufacturer. the recommended capillary id is 0.15 mm but i am using 0.25 mm but this is for both (FID & MSD). now almost i identified the problem. today i have changed the capillary with right length and new Y splitter. tomorrow i need to check the result. my only doubt is whether i have connected the Y splitter or not. i do not know how to check the leak at Y splitter
Regards
Senthamizh
Well, you should know if you have the splitter connected, don´t you? :-)))
As for leak checking: Standard practices apply.
1. Ifyou have, use a He-Leak-Detector (supposing that He is your carrier gas).
2. More easier, you a water/liquid soap mixture and carefully drop something on the spillter. Check for bubbles.
If you suspect a leak to the MS: Tune the MS to mass 40 check for a unsusal high base line. Add some argon from a small gas tank with jet to the splitter and check wether the base line increases or shows a peak.
Checking for a leak to the FID-line is more difficult: You might use the same technique as for the MS if 1+2 dont work. Spray a small amount of a 100% methane for a couple of seconds to the splitter. If the baseline of the FID shifts, you have leak to this side.
Good Look and Good night (its 9pm in Germany)
Stefan
Using water/soap mixture (snoop) to check for leaks in a GC is not the best of ideas. If you really have a leak and the liquid makes it into the column or worse the detector you are in for some serious cleaning and you'll have to change all columns/transfer lines.
Hi Bert!
Basically you are correct. This is why I rated this as possibilty #2 :-)
However, have you ever had the problem that the the fluid made it into a column? I never had this problem.
Regards from Hannover
Stefan
Hi Senthamizh, what kind of "Y" do you use? A simlpe "Y" with the same inner diameter in the three way?
Thanks
Vittorio
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