frequent FID lighting problems

[ece]

I have an Agilent 5890 cool on column direct injection with a .32 mm x 15' metal column and a .53 mm x 2' metal retention gap. I have frequent lighting problems with my FID, despite excellent air (350-400 mL/min) and H2 (35-40 mL/min) flow rates. This always happens when I turn the unit off for any reason (such as doing maintenance) and turn it on again. I always let the unit heat up first to at least 350 deg. C before lighting it, and if it doesn't light I always check the flow rates. I usually bump the flow rates up by about 10 mL/min on both air and flow, and normally then it lights.

But this recent activity, I had to trim the guard on the inlet end and replace the septa (that's all I did, didn't even touch the detector). To do that, I have to turn the unit off first. Now the FID will not light at all, even when I had it at 375/37.5 and then bumped it up to 400/40. It still will not light. Glow plug is glowing fine, and I also tried lighting the stream with a cigarette lighter as well. Nothing seems to be working, there is not a pop and now not even a signal showing up. FID detector is ON, I checked that too.

When I called Agilent tech support, they say that when I turn the unit off that detector immediately starts to cool down rapidly and draw condensation from the atmosphere or from the flame. I didn't have the detector lit though when I turned the unit off, so I'm guessing that some condensation from the atmosphere has gotten in there, or that there is some kind of blockage in the jet that is artificially changing the flow path.

Now, my only option is to take the detector apart and sonicate the jet and collector bore. What should I do if that doesn't work?

Can anyone give me any advice on what to do?

[Ron]

Go ahead and take the detector apart and clean and dry everything. I had issues with a few 5890 FIDs lighting, one time when the detector was opened up we literally poured out the condensed water. That shouldn't stop the detector from lighting with a lighter, but I've seen stranger things.

[ece]

I did take it apart and clean it, dried with N2, I have never seen any condensed water on there at all. When I re-installed the detector end of the column I always get peak tailing, every single time I do this this happens. What I have been doing in the past to correct this is just to cut the column end by about half a foot, and usually that takes care of the problem. I want to know what I can do to properly install it without having to cut my column all the time.

Thanks

[ece]

called agilent it turns out our jet is the wrong one (we have a 5890 and the one we bought from restek is a 6890), it's too short! we have gotten lucky in the past lining it up correctly, and now with the short jet it is not lining up properly and creating a dead space, which i'm sure created my tailing issues. as for my lighting issues, could this be related? the detector gases do not come through the jet, but at the tip of the jet. could mis-alignment of the column to the jet cause lighting issues by somehow diverting the flow path?

[Carvone]

I worked on a 5890 where you had to gently blow on the heater coil as you hit the ignition button, and it would glow a brighter orange and ignite.

[ece]

yeah someone told me that too, but the glow plug was not the problem. also, if you blow on the glow plug, does that not risk moisture contamination?

[Carvone]

I'd never thought about moisture contamination before. I blew from a distance very gently, but I suppose there may be some risk of moisture contamination. I would always condition the column for about 20-30 minutes after turning on, so I I would hope this would stabilize the detector by then. I never noticed any erratic results from times I needed to blow at coil and times I did not.

Does anyone else know anything about if gently blowing on heater coil can cause moisture contamination?

[skunked_once]

if you blow on the glow plug, does that not risk moisture contamination?

Does anyone else know anything about if gently blowing on heater coil can cause moisture contamination?

If your detector is heated to 350 C, try putting your fingers on the detector top where the glow plug is located and ask yourself if moisture contamination is likely

I don't expect anyone to take my advice and will not be held responsible if they do

[Ron]

The moisture accumulation in the 5890 FID tends to occur lower in the detector.

[AICMM]

The center of the heater on the HP 5890 is a little over three inches away from the exhaust of the detector. Furthermore, the heat transfer is through the little neck just above the heater base, hardly the ideal. So, yes, you can get moisture in the upper reaches of the detector which explains why I find rust on the upper teflon insulator sitting on top of the collector on many of the detectors I work on. The problem is further compounded by the fact that the detector cannot always be held at 350 C as in the case of using wax or Alumina columns. For people using chlorinated solvents, I recommend putting a heater on top of the FID to supply additional heat in the upper reaches of the detector.

Would I worry about blowing on the detector, not at all, but I usually use a lighter.

Best regards.

[ece]

The moisture accumulation in the 5890 FID tends to occur lower in the detector.

ok, good to know. would this same thing happen if, say, you didn't turn the detector gases off and you were cooling the entire unit down, and the moisture from the flame accumulated on the detector end?


Skunk, i don't find that funny at all. when i see there are responses to my posts, i am hoping for useful input, only to find someone trying to get GC newbs to burn themselves! sick!

[skunked_once]

ece,

My sincere apologies I was trying to inject some humor into the forum and went overboard this time.

ok, good to know. would this same thing happen if, say, you didn't turn the detector gases off and you were cooling the entire unit down, and the moisture from the flame accumulated on the detector end?

Yes, this could happen and has happened to me when I cooled down the detector and left the flame on producing water as the combustion product. The result was that the detector shorted out and produced a maximum baseline signal.

Once again, my apologies.

[ece]

no worries, i was actually just pulling your chain. it was kinda funny, cause i've seen it happen before (not to me, fortunately)

[Peter Apps]

FIDs ignite better with a richer mixture, turn the air down to about half its usual setting, press ignite until you get the pop (which will be louder than usual), then turn it up again.

What gas and at whct flow rate are you using as carrier ?

Peter

[Russ]

Don't know if you are still having this problem but I recently had a problem where the glow plug was working but it would not light a 6890 FID (similar to 5890 but lights automatically) even if I blew on the plug. Over time the coil for the plug can get pushed back into the plug. I carefully pulled the coil out slightly, reinstalled the plug, and everything worked fine. Have also noticed this issue with 5890's but they would generally ignite if I blew on the plug.