Converting "capillary-optimized" FID to universal FID (6890)

[Gaston]

Hey guys,

Well, it appears I was overly optimistic in thinking I could detect CO with a TCD having argon as carrier (because I need to detect H2). Since I have both a TCD and an FID installed in the GC, I'm looking now into installing a methanizer and using the FID for CO detection, while leaving the TCD for H2 detection. Moreover, this seems to be the standard configuration in most papers I've read.

I was reading Agilent's manual for the methanizer and it lists the packed column FID (the "universal" version) as a requirement. Unfortunately, I have the "capillary-optimized" version, meaning then that I cannot install a methanizer (without some modifications, at least).

So, the question now becomes: is it possible to convert the capillary column FID to the universal version without having to replace the whole detector? I was looking at the parts list here and it seems to me that only a few parts are different. Therefore, I thought about buying the parts, disassembling the FID, and installing the "packed-version" parts myself.

The new parts would be (according to me):
18710-20119 Jet for packed column (0.018 in. id)
G1531-80580 Base weldments
G1531-00160 FID Seal Insulation
19231-80520 Packed Column 1/8 in. adapter
19234-60715 Nutwarmer insulation
19234-60700 Nutwarmer Cup Assembly

Most parts are relatively inexpensive, except for the base weldment. Still, the price is significantly less than a new detector.

Is this possible, or is it again overly optimistic thinking? Has anyone attempted this?

As always, many thanks in advance for your help.

[GasMan]

The basic problem is that the capillary only version of the FID will not accept 1/16 tubing, which is the exit tubing from the methanizer. You could first try using a short length of 530 metal tubing which will go into the present FID and with suitable ferrules and a union, connect this to the 1/16 tubing from the methanizer. You can least check out if your analysis will then work before investing in a new FID body.

Gasman

[Gaston]

That sounds like a good idea. I will try this out, so I will get the methanizer and the parts to attempt this.

The other question is how to use the TCD and FID simultaneously for analysis. We had talked a bit about that in a previous thread and it seems that using a splitting tee after the column could be a good option. However, I'm a bit worried that could be a problem for quantitation, in that I imagine that the amount of sample "sent" to each detector from the split could change (e.g. by changing a different carrier flow) and then the calibration wouldn't work. Is this a reasonable concern?

What I'm thinking now is making a TCD-to-methanizer connection with 1/16" tubing. I guess that the TCD vent tube can be fitted to a 1/8" ferrule and nut (as in the TCD to FID series connector), using a reducing union, and then 1/16" tubing to the methanizer. Does this sound reasonable, or am I missing something?

Here's a little drawing: http://i.imgur.com/CDc7dyV.jpg

[GasMan]

Agilent usually brings the exit of the TCD out into the oven when they connect the TCD in series with the methanizer. If you remove the cover of the TCD, you will find that the TCD exit line has a clamp on it down near he base. If you remove the clamp, it is possible to bend the exit tube so that it will exit into the oven. You can then connect to the methanizer inlet, which also is usually inside the oven.

Gasman