FID Inlet Clogged/Blocked on 6890N; Need Advice

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Hello,

I am an undergraduate researcher and I've had about a years worth of experience with gas chromatography. I am currently operating a Agilent 6890 N GC. I have run into some issues of late and was wondering if anyone has any advice for me.

Essentially my issue consists of the following details:
  • I was observing variability in FID readings as if I had a leak somewhere. I checked all feed lines and found no Issues and determined it must be within the GC. I preformed the leak check that Agilent recommends on YouTube, and found that the leak consisted somewhere from the front inlet to the FID. After tightening pieces and working my way down I came across the connection between the column and the FID itself (downstream on the column respectively).
  • When I gave the column a slight tug it fell right out of the connection (hence I deduced the leak was there). But my problems got worse... As when I removed the fitting that connects the column to the FID through the roof of the oven, I noticed the graphite ferrule had been completely obliterated(smushed to a flat top and unable to see through).
  • From the Agilent manual I realized that the capillary column is supposed to slide approximately 48mm through to the FID Jet. when I attempted this it would not even pass the beginning and when I removed it, appeared like I had gotten graphite and pieces of glass on it. I thought that this likely indicated that the FID jet was clogged and I reviewed steps on how to remove and clean it.
  • Following removal of the FID jet it was found that the jet wasn't the problem at all (I could see clearly through it when shined up against a light and acetone passed smoothly though it). When I shone my torch from my phone through the oven however, I was unable to see the light. Hence I thought that maybe the actual inlet piece was clogged or had pieces of a ferrule/column stuck inside.
  • I tried removing a segment of column and using that to poke the clogged material through from the top down. This did not work so I instead turned to a 0.4mm 3D nozzle needle to poke the junk out. This did work, and I saw broken pieces of column and pieces of graphite falling to the ground. (I of course rinsed the needle with acetone before beginning this procedure to avoid contamination). Throughout this procedure I used a flashlight underneath to view exactly what I was poking out until it became clear there where no more contaminants in the path line.
  • Following proper reinstallation of the FID components, I tried to reinsert the column back through the FID Inlet, but to no avail. It seemed to still be clogged. I do not know what to try next.
I think it is also important to note that when I asked a graduate researcher about this issue she replied that she and others in the lab group had known about someone who forgot to remove a ferrule from the inlet and then reinstalled with a second ferrule, and basically fused it shut. Would this be what is blocking it and if so how do I remove it? I think the issue or the cause of the issue is that someone had tightened the nut too tight where it forced the ferrule to collapse the glass column in place. I really just don't know what to try next and I want to avoid using the needle to poke stuff through the inlet as this process terrified me as I am well aware of the costliness of the FID components. Previous researchers had just connected the column tip to the bottom of the connection. This isn't the correct way to do it, but if it works should I just do this or will my problems of irreproducibility in FID results remain.
Thanks,
I was unable to attach the image. any help with that too would be appreciated. let me know if its even necessary.
Agilent sells a cleaning wire that one could insert through the FID jet tip to clean any pieces out of the jet. Part #5180-4152

From Agilent: The Procedure for FID Jet Cleaning is as follows.
You can use FID Cleaning Kit (PN#9301-0985) for this procedure.
1.Run a cleaning wire through the top of the jet. Run it back and forth a few times until it moves smoothly. Be careful not to scratch the jet. (Do not force too large a wire or probe into the jet opening or the opening will become distorted. A loss of sensitivity, poor peak shape and/or lighting difficulties may result if the opening is deformed.)
2. Fill an ultrasonic cleaning bath with aqueous detergent, and place the jet in the bath. Sonicate for five minutes.
3. Use a jet reamer to clean the inside of the jet.
4. Sonicate again for five minutes.
NOTE: From this point on, handle the parts only with forceps!
5. Remove the jet from the bath and rinse it thoroughly, first with hot tap water and then with a small amount of GC-grade methanol.
6. Blow the jet dry with a burst of the compressed air or nitrogen, and then place the jet on a paper towel and allow it to air dry.
Wow! it seems to me that after you have the jet out, you should be able to shine a flash light back up through the opening from the oven to you looking above it and check for clearance. The column goes back up the jet from the bottom and won't go through the jet orifice on top.

The ferrule should seal around the column and into the seat at the bottom of the opening that holds the column up into the jet. If that opening is blocked, where the ferrule was smashed around the column, you should just be able to grind it out of there with the sharp end of a nut pick.

To properly install a column:

1) slide the nut on the column. then the new graphite ferrule (tapered side up, pointing toward the jet).
2) cut the end of the column flat with a column cutting tool. You don't want graphite inside your column.
3) slide the column up into the jet tube until it touches the base of the jet.
4) push the ferrule and nut up into the fitting inside the GC oven. Finger tight it to the column. This is especially easy when you're using graphite ferrules.
5) pull down on the column about 1-2 mm. You don't want it touching the base of the jet.
6) tighten the ferrule. It's graphite so it's really soft. It doesn't take much to make the seal. 1/8 of a turn or so should be sufficient.
7) pull down on the column to see if you can pull it out. If the column moves, it was too loose. Redo 4-7. If you can't move it, you're done.

it does no good to put too much torque on the fitting inside the oven. You can break the column. If you ever use graphitized vespel ferrules, you can break the column if you're not careful.
Thank you guys. So, in response to the first post, I do not believe the clogging is within the FID jet. Would purchasing this kit assist in clearing the opening before the jet? When I shined a light through the jet opening I could see the light through.
Thanks for the advice on the second post, I did shine a light through the opening earlier and I thought I cleared the majority, if not all, of the debris out of the opening. I will try using a nut pick and I will re-remove the FID jet and reinspect it to ensure it is clear of debris.
Any other advice on what I should do next that would be great.
If you have it all cleaned out and you install the column correctly, you shouldn't have any problems.
So, the FID jet is cleared: I was able to remove the jet and I slid the capillary column through it to the appropriate length. The column still won't fit through the orifice at the roof of the oven, however. Is the issue with the weldment? Is it possible that when someone tightened to much it ended up like constricting the opening? I can clearly see there is no more debris in the line so this is like my only explanation. I tried sticking a piece of column down the top and it wont go through the bottom at all.
StarMan007 wrote:
So, the FID jet is cleared: I was able to remove the jet and I slid the capillary column through it to the appropriate length. The column still won't fit through the orifice at the roof of the oven, however. Is the issue with the weldment? Is it possible that when someone tightened to much it ended up like constricting the opening? I can clearly see there is no more debris in the line so this is like my only explanation. I tried sticking a piece of column down the top and it wont go through the bottom at all.



Sounds like it is clogged by a piece of ferrule in the makeup gas adaptor. Usually those FIDs have a large 9/16" nut holding the adaptor to the bottom of the FID inlet. You should be able to remove that and check to see if it is blocked. If that is clear then look at the bottom of the FID above that and below the Jet and see if you can see through it. Can remove the jet and shine a light up from the bottom and you should see it when looking down from the top with the jet removed, if not then it is clogged there.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
Sounds like it is clogged by a piece of ferrule in the makeup gas adaptor. Usually those FIDs have a large 9/16" nut holding the adaptor to the bottom of the FID inlet. You should be able to remove that and check to see if it is blocked. If that is clear then look at the bottom of the FID above that and below the Jet and see if you can see through it. Can remove the jet and shine a light up from the bottom and you should see it when looking down from the top with the jet removed, if not then it is clogged there.


yeah so when I removed the jet I can see clearly through without an issue. here is an image of the bottom and top of the FID (I tried the best I could with the lighting)
Image
Image

I think that the small inner ring by the hole on the underneath of the FID is possibly an old ferrule stuck in there and I can't seem to poke it out. What are your thoughts?
StarMan007 wrote:
I think that the small inner ring by the hole on the underneath of the FID is possibly an old ferrule stuck in there and I can't seem to poke it out. What are your thoughts?


When I was working, I'd likely remove the entire FID from the GC (when my pointy-haired boss was away), and take apart the whole thing to inspect/clean.
Consumer Products Guy wrote:
StarMan007 wrote:
I think that the small inner ring by the hole on the underneath of the FID is possibly an old ferrule stuck in there and I can't seem to poke it out. What are your thoughts?


When I was working, I'd likely remove the entire FID from the GC (when my pointy-haired boss was away), and take apart the whole thing to inspect/clean.


Ha ha! Ok, I don't know if I should do this without prior approval though because like I am only an Undergrad, and I don't have a ton of power when it comes to this stuff. But I can try asking my Lab PI and seeing what he thinks about it. Thanks!
I just ordered capillary inlet cleaning wire for the FID PN: 5180-4153. This will hopefully be a cheaper solution than removing the entire FID and possibly screwing it up. I am going to try using this before I go ahead and take the FID off of the unit.
Ok, if I where to take apart the weldment and inspect it, what would be the steps for this and how would I go about it without breaking anything? Is there a manual anywhere or instructions on how to do these steps?
StarMan007 wrote:
I just ordered capillary inlet cleaning wire for the FID PN: 5180-4153. This will hopefully be a cheaper solution than removing the entire FID and possibly screwing it up. I am going to try using this before I go ahead and take the FID off of the unit.


This did not work. The cleaning wire is much too thin for this purpose. I removed the FID and am currently working to clean it out. I ordered a replacement weldment from Restek (agilent had a $1000 more expensive part that is the same). The Restek part #23053 should work as a valid replacement for the current weldment as that is the only thing that is currently "broken".
What is it about the weldment that you think might be broken? (Sorry if I missed it in one of the older posts). Did you take the collector apart like in the link ConsumerProductsGuy shared?

I know you mentioned being reluctant to, but honestly - just don't throw it against the wall. They're pretty decently sized metal and teflon pieces, nothing super delicate imo. I'd be way more comfortable letting someone new to the instrument do that part than having them install a new weldment.
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