Spiking/Noise on FID

[jwlee]

I am having a recurring problem with a Shimadzu GC-2014 w/ FID. I have the same noise/spiking with every test, and it shows up on a blank run as well. I have changed the column and it is still showing up. Could this be due to a dirty FID collector or dirty FID jet? I have also cooked the column (packed stainless steel) and still have these peaks showing up. Any help would be much appreciated.

[chromatographer1]

Dirty FID, packing being released from the column, electrical contacts not making good contact.

Lots of things to check. Clean the FID first.

best wishes,

Rod

[uzman]

In order to localize the problem , remove the column connection from the FID detector , and close the inlet with a septum.

Heat the detector to 200 C and don't light the flame.

If the problem continues , it is an electrical problem , and mostly originated from the cables connected to collector.
Carbon particles entering the cable insulation may cause this , and it needs cable replacement.

If this is not the case , now light the flame , and if the problem appears, it is originated from : gases , gas filters , FID jet and collector so clean accordingly.

If none of the above , then suspect column , and check column glass wool plugs.
Electronic boards failure , and glitches coming from the electrical supply are other possibilities.

Good luck.

[jwlee]

Are you saying to light the detector with the column disconnected from the FID side? I just want to make sure this is safe.

[chromatographer1]

As long as you have the opening into the FID closed off, it is safe to light the detector.

The only gas flow missing is the tiny flow from the column itself. The air, hydrogen, and makeup flows should be the same as when the column is connected.

If you don't have a means of closing the opening, take a spare or used septa and after cutting the column a few inches below the detector nut, press the septa onto the column where it was severed from the rest of the column, blocking the flow of gases into the oven. This will suffice.

Then reinstall the column after the troubleshooting is done.

best wishes,

Rod

[uzman]

Since the column is a packed stainless steel column , as you described , I recommended using a Shimadzu septa to close the detector inlet.

You may also use a no-hole ferrule , but I couldn't locate such 5mm ferrule , since Shimadzu uses 5mm standart.

As Chromatographer1 stated , it is safe to light the detector under this condition.

You may even heat the column passing the carrier gas ( except Hydrogen ! ) during this process.

[chromatographer1]

Oops, I forgot the content of the initial post.

The best solution is a SS cap, on the 1/8 or 1/4" detector inlet, available from your local vendor.

Uzman is correct in suggesting a septa inserted inside the nut will also effectively seal the detector. A large graphite no hole ferrule should deform enough to close off the detector.

A chemwipe wrapped around the column end might catch evidence of any packing the column might be releasing into the detector when attached.

best wishes,

Rod

[jwlee]

Thanks for the help! I have eliminated electical, gases, gas filters, and jet collector. I hooked the GC back up exactly as it was. Now, I am getting no peaks. Checked all connections and they are good. I was wondering if purge flow rate or column inlet pressure could have some sort of effect? I haven't changed any settings either. My carrier flow rate is 40 ml/min, column inlet pressure is 0.5 kPa, and purge flow rate is 0.1 ml/min (which seems extremely low, but I can't get it to go higher. My carrier cylinder is 3/4 full and set to about 1000 kPa. Any ideas?

[seamoro]

Ok i am really interested in how to do this as i have the exact same problems. Uzman you were saying in order to localize the problem, remove the column connection from the FID detector , and close the inlet with a septum.
Heat the detector to 200 C and don't light the flame. ?
so remove the column from detector....are you saying cut the column and plug the cut end that is entering the detector and plug the cut end of the column. then ramp up to 200 degrees without turning on the flame? what is this suppose to do or what am i suppose to obeserve? indicates electrical problem?
then you say "If this is not the case , now light the flame , and if the problem appears, it is originated from : gases , gas filters , FID jet and collector so clean accordingly" so when lighting the flame" im not sure what you mean here....light the flame with cut column and cut column entering detector closed off with septa....so what am i suppose to oberve here??...can i inject a sample on the column when i have this done and obeserve the baseline?

[uzman]

Dear jwlee,

Please check if you connected the column to the injector side properly.
0.5 kPa is a very low pressure ( is it 50 kPa ? )

For metal column connections you must use aluminum o-rings between column and the column adapter.

Also check the detector high voltage cable. There is a fork type connection which fits on the FID nozzle.

Dear seamoro,

We are talking about metal columns , and these columns can be disconnected using a spanner , there is a column adapter fitted inside both the injector and detector side.

If you are talking about a capillary column , you may cut a few centimeters below the detector and close the end with a septum , in order to prevent hydrogen leakage .

Do not close the column outlet , it is not necessary , let the carrier gas flow ( except Hydrogen ! )

Under this condition , heat the detector to around 200C ( without flame ) , if the problem continues , this means it is electrical problem. ( Normally no flame , no signal )

If the GC passes this test ( no flame , no signal ) , then light the flame and you will most probably face the problem again.
Now you may check gas filters , FID jet etc. and clean accordingly.

[uzman]

Sorry , there is a missing statement.
After checking the detector without flame , you continue with the flame.
If you face the problem , possible causes , dirty FID jet , dirty hydrogen , dirty air or dirt somewhere in detector housing.

If no problem , connect the column to the detector again , and wait for the problem.
Possible causes , dirty carrier gas , dirty column , dirty gas filters , dirty liner etc.