Chromatography Forum

i've done all the recommended maintenance. scrubbed the inlet etc. the tune passes, but my breakdown keeps climbing. up to 38% right now. using RESTEK's version of the Agilent focus liner...is there anything else i can do?

Are you using glass wool in the liner? Probably not but if so, try one w/o. What are your GC parameters? (i.e., inj temp, init oven temp inlet pressure, Split or Splitless, Pulsed Pressure or not, column dimensions and flow rate?). If it's an Agilent GC (6890/7890) have you removed and cleaned or replaced the split-vent line? It's the copper tube running along the left top of the instrument connected to a carbon trap at the back. This is the most common place I have seen contamination that cannot be removed by typical routine cleaning and maintenance. It is fairly easy to do.

thanks Ty!!
took out the GW inlet liner and replaced with a single gooseneck... 4% Endrin breakdown. I've had this thing totally torn apart and replaced the split vent tubing with certified clean copper tubing from agilent.
using a DB-5MS 30x.25 .25film column. inlet is pulsed splitless 250c carrier gas velocity is 33cm/s. I think i've got the endrin breakdown licked, now i've lost all my chlorinated compounds in my spikes and LFB...40% recoveries.... have to look at my extraction process...i think.

What is the Mol Weight of the Chloro compounds? I've never actually run Endrin or this specific method but I know that the glass wool will cause thermally labile compounds to decompose incredibly. However, it will allow for better transfer of the heavier analytes (i.e., bromo or chloro compounds) as there is more surface area in the liner for heat transfer. If removing the glass wool causes the drop in sensitivity of the chloro compounds (assuming it's not related to extraction) then try the Restek Sky liners w/wool. I believe the wool in them during the deactivation process so there are no terminal Si-OH active sites. I used to run 8270 and used Restek's Siltek coated w/deact wool (not the Sky but almost as good) and I would get about 5% Decomp of DDT for the 8270 degredation test. This wool was also necessary for my chloro comps as well as heaviy PAHs.

Hope this helps.

How old is the injection port? There comes a time when cleaning will not work. It has been tough for me to accept an injection port as "consumable", but for endrin breakdown it is.
I use the Restek direct liner ( part # 21055) with good results. I just replaced my liner, seal and clipped my column today. I went from about 12% to 0% breakdown.
Oh 50psi pulsed splitless injection @ 250C.

just had the PM on the gcms in question...14% endrin breakdown....i'm going to throw the #$%^&$ing thing out the window...i've got my PT in-house and the clock is ticking.

I hate PTs (Pointless Tests). That's why I went back to research. j/k
What kind of liners are you using now? What others do you have on hand? You are still getting 14% on a liner w/o glass wool?

If there is a trade off between the types of liners can you run the PT twice? Once on the glass wool liner for the chloro compounds and then on a non-wool liner for Endrin? As long as your SOP doesn't contain specific language about the type of liner you use you should be fine with doing this. Then you can spend more time finding a better solution after the PT study is done.