FID ignition failure

[skazareth]

Hi all.
I am using Clarus500 PE GC. Question here is, does anyone know what are posibilities causing my problem : fail to ignite FID. I tried many times but only heard the ignition "pop" sound but still not ignite the detector..this happened many times. I checked H2,O2 gas, they are in a right flow and correctly set. But for the column (ID : 320um), in FID I couldn't insert the whole 7cm, maybe only 6cm. Please anyone help me.

addition : for methanol based sample, what is the range for "split" you people recommend?

[Peter Apps]

How do you know that that flame is not ignited ? If you are relying on the GC readout you need to check by holding a cold shiny piece of metal or glass above the detector. If you see condensation the flame is burning and you have an electronics problem or you have the wrong setting for the flame ignition offset.

Are you measuring actual flows at the detector with a flow meter ?, or relying on the GC readout.

You should be using air, not oxygen. Do you use make-up gas ?, what is the flow rate ? too much make up gas can extinguish the flame.

Your not being able to insert the column the specified distance into the detector suggests that there might be something partially blocking the flame tip.

Peter

[DR]

Popping is frequently associated w/ too much hydrogen.

[Dan]

I will second the comments by Peter and DR in that the either the hydrogen flow is too much or that you are using oxygen instead of air.

Since you tested the H2 flow and found it to be OK, then try switching the O2 to air.

I rememebr my first hands on experince with a GC instrument many years back. An older graduate student was showing me and a friend how to get the GC up and running. We kept getting the same result: the FID would "pop" but not stay lit. The H2 flow seemed to be correct. After several hours of gently trying to persuade the (very old) instrument to work and just before we took a hammer to the thing, we noticed that the air cylinder had been replaced with an oxygen cylinder. Swithing back to air solved the problem.

Regards,
Dan

[skazareth]

Thanks all for replying..appreciate it very much.

Answer to Peter, I knew that the FID wasn't ignite from the diagram in navigation. It shows 0.01mV and only fluctuate when the pop sound, and stay 0.01mV again. Then when the auto-sampler done doing her job (sampling thing) it shows no peak at all. I suppose, methanol will show a peak at 1.0-1.1 min..but this time, no peak.
For the flow rate thing, I am sure the programmed and actual setting are correct. 45 for H2 and 450 for O2. <---Perkin Elmer suggest this.
About cold shiny thing on the detector, I will try to see what can I do tomorrow at the lab (I am in house today..it is Sunday in Malaysia now)

Many of you suggesting I should change gas, from O2 to air, can I have a detail about this? What flow rate, have to change setting or not, etc.

Thanks again every one. I really hope my problem will gone because its been 3 months already..our vendor keep come and go fixing this FID. They said, if we need to get new FID, I have to wait for another 4 months.I cant wait 4 months..

[AICMM]

Skazareth,

Switch to air first. Set air flow to 450 (typically set at 10X the hydrogen flow)
If that does not fix it, measure (not program, measure) the flows to make sure the EPC is providing the proper flows for each component. This also helps troubleshoot other issues like a clogged flame tip like I recently found.

Regarding replacing the FID, there is hardly anything with the actual detector that can go wrong (which is one of the reasons so many love the detector). Yes, flows can be off, EPC's can go bad, ignitors fail, and electronics fail, but the FID body itself is really just hunks of metal so look every where else before looking at that route.

I'd bet a Snickers bar that it is the air versus O2.

Best regards.

[skazareth]

now it work..silly vendor.
Ive changed the gas already..from O2 to compressed air. Set up at 450mL/min. Ignite well and flame well. (but the signal I get 2.58mV when ignition starts, then stays at 0.08mV, is it normal?) Gives me peak very well. Very sad with the low-quality-vendor we have. I guess they dont have much experience. They are selling this thing, why they not realize this problem? Is it also happen to your vendor out there? Luckily I have you guys.

I'd like to tell that I am newbie in this separation technology thing..Years back, I work with DSC, TGDTA, DMA,LabReactor. This year we bought UVVIS, GC, GC-MS and FTIR. All are under my supervision..it IS a burden (more machine, more work, salary still the same..), but its ok, new thing new experience. I hope all my expert friends here can advice me.

Thanks again.

[isabellerf]

Hi,

I completely understand your frustration Skazareth!

I also have a FID ignition failure problem. This morning I had to change the air cylinder and while doing so I wanted to close the valve on the manometer so that exterior air wouldn't come in while I was switching cylinders. But, the valve wouldn't stop to close. It kept going on and on. So I finally stopped turning but I have no idea how much I turned!

Then, when I installed it all back, I opened it, but then again there was no stopping!

I tried to ignite the FID, but nothing came.
Actually the first time I heard a REALLY loud pop then no flame. Afterwards, I never heard a pop sound (and no flame) when I pushed the button. I turned the gases (H2 and air) on and off. I opened more and more the air valve on the manometer.

You all talked about verifying the flow. How can I do that?
I'm new to the FID detector. And I have a really old GC so I can't look at any electronical data for flow!

Thank you very much!

[Peter Apps]

It sounds as if you have no air flow to the FID. What kind of GC do you have - the details of measuring FID gas flows will differ slightly. Does the low pressure gauge on the air cylinder regulator (I presume that this is what you mean by manometer) show any pressure ? If not I fear that you have damaged the regulator. Is there an air pressure gauge on the GC ?, does it show any pressure ?

Peter

[isabellerf]

Hi Peter,
thanks for the reply.
I have a Agilent 5890 GC.
I do see a pressure on the low pressure gauge on my regulator. But on the GC I cannot see anywhere if there is an air pressure.
This morning I tried to ignite the flame with more or less H2 or Air coming in (with the "inlet" on the GC) before pressing the ignitor.
Depnding on the amount of H2 that I let in, I could see, or not, the orange light of the ignitor. But that didn't change when I changed the air pressure (but the thing is: I never touched the H2 pressure on the cylinder or regulator!)

Isabelle

[skunked_once]

Isabelle,

You should measure the flows of air and hydrogen at the detector to make sure they are correct. There is a small adapter for this (Agilent part # 19301-60660) that fits into the top of the detector for that you connect to a flow meter. Flows should be about 350 mL/min for air and 35 mL/min for hydrogen. Be sure that the auxiliary flow is turned off when lighting the flame.

[isabellerf]

thank you very much.
I'll try it next week.
Have a good day,
Isabelle

[Peter Apps]

Hi Isabelle

It is a very long time since I worked on a 5890, but if you look inside the opening panel on the left hand side you will find a set of pressure gauges, one of whihc will be for air, one for hydrogen, one for make-up. This is where you do the gas flow rate adjustments. You do NOT adjust the hydrogen flow rate to the flame by changing anything on the inlet gas flow - this is just for changing flow through the column. What carrier gas are you using by the way ? You really need to study the operators manual for the instrument, which gives you all the information that you need about flow rates and how to set and measure them.

Peter

[skazareth]

allright , now my problem has solved. Thanks again all. So we can continue talk about ignition matter in here..to isabelle, good luck!

This is the thing that i have learned recently :The air tank will be finished within just a week when we use GC often. (flow rate of 450mL/min)

As i said before, GC is new to me. When i use TGDTA, DSC, DMA and all that, i only use nitrogen or argon that last for 6 months (if i use each machine 3-4 days a week). but now, i'm going to need like 4 cylinders of purified air a month just for GC. i've ordered 30 cylinders.

Before i forget, i want to ask about the pop sound. Why does my FID, when it ignite, the pop sounds like this : "pop-pop-pop-pop-pop". 5 times of pops, not once. is it normal?

Thanks..

[AICMM]

skazareth,

Yes, you will use plenty of air. One of the disadvantages of FID. If you don't like that and you have the right analytes and you have some extra money laying around, there are alternatives. However, it is not generally considered that big a deal to buy that much air. I may be mistaken, but you are probably paying rent on those cylinders so you might want to only keep 3-4 on hand and order 2 to replace 2 when they get empty. Could save you some pretty decent money.... You could also look at air compressor but this should have the appropriate filtration or your baseline could get very noisy.

Pop, pop, pop is still a flow not where it should be at ignition. On the 5890, when you with the ignitor it cuts down the air flow temporarily. If you don't use the ignite button but use a match instead it might cause the multiple pop. On the other hand, multiple pop is not a big deal if flame stays lit for you.


Best regards.