external oven with 6890?

[AZBiodiesel]

Hello,

Is there an external oven that can be hooked up to a 6890 with split splitless and FID?

Thanks,

[aidnai]

I am not aware of anything off the shelf. But I have built a custom heated zone on a 5890 and used the AUX zone control. It required quite a bit of mucking about, not sure I recommend it.

What are you trying to accomplish?

[Johnny Rod]

You can get creative, for example if you have a single channel instrument and you want to add a methaniser (nickel catalyst) tube then Agilent usually fit this in the place of the other inlet and use that heated zone.

[AZBiodiesel]

I have two methods that require columns that are not temp compatible. One column 250 C wax, the other 400 C. I want to put the low temp column in the external oven, as it is just 50 C isothermal, headspace sampling for methanol.

I have spoken with SRI since their units have small modular looking columns. Got quoted about 2500 for just the oven section. The oven can only do isothermal temps as it won't connect to the 6890.

I will probably call agilent tomorrow and see if we can hook the 7890 external oven onto a 6890, not likely though...

[Johnny Rod]

400C sounds like molecular sieve. I presume you mean the max temp rather than the analysis temperature? You could recondition your mol sieve at 250 for longer if need be and keep both in the same oven, we have GCs with mol sieve and Haysep Q (max 275C) so have to do the same.

[Peter Apps]

I am having trouble picturing what it it that you are planning to do.

If you are planning to have one column in the extra oven, how are you going to inject and detect ? If your plan is to use the existing injector and detector then you need heated transfer lines to and from the column in the external oven. Then what is going to happen to the column that is not connected ?, or do you plan to split to two columns at the inlet and join them again before the detector ?

If all this is to save swapping columns then the solution is probably worse than the problem.

Peter

[AZBiodiesel]

Ok, back inlet is COC hooked up to a DB5-HT, FID, method max temp is 380 C. ASTM D6584

Front inlet, is Split splitless, With 7694 Headspace line plumbed directly into the inlet. EN 14110

I want to be able to leave the back column in as is. The front inlet would be connected as is but the column would be routed up out of the oven (somehow i need to find a pathway), into the external oven, then out, back down into the oven and into the front FID. The analyte is methanol so as long as the external column lengths are short there is no need to insulate them...

The external oven will be set at 50 C isothermal. The only problem I can see is that when making a run on the back column, the lengths of column in the oven will be exposed to high temps, as will the front inlet and FID.

I need to be able to run both methods at the same time. I have no space left in the lab for a second GC, and I really want to avoid switching columns in and out. Not a big deal for me but I have 4 lab techs and things can go wrong...

[Peter Apps]

Ok, now I get a clearer picture of where you are gong to and coming from. Two thick aluminium slabs with the column between, two of these; http://www.dbktechnitherm.ltd.uk/cartridge.html, a new mount for the inlet and detector so that the stems go though the slab, and a pile of ceramic wool insulation, and away you go. A lot depends on how comfortable you are with DIY setups.

Peter

[James_Ball]

Ok, back inlet is COC hooked up to a DB5-HT, FID, method max temp is 380 C. ASTM D6584

Front inlet, is Split splitless, With 7694 Headspace line plumbed directly into the inlet. EN 14110

I want to be able to leave the back column in as is. The front inlet would be connected as is but the column would be routed up out of the oven (somehow i need to find a pathway), into the external oven, then out, back down into the oven and into the front FID. The analyte is methanol so as long as the external column lengths are short there is no need to insulate them...

The external oven will be set at 50 C isothermal. The only problem I can see is that when making a run on the back column, the lengths of column in the oven will be exposed to high temps, as will the front inlet and FID.

I need to be able to run both methods at the same time. I have no space left in the lab for a second GC, and I really want to avoid switching columns in and out. Not a big deal for me but I have 4 lab techs and things can go wrong...

To avoid overheating the wax column if you get the external oven set up I would use short lengths of guard column to run from the inlet and detector out to the external oven and use press tight connectors to connect those to the wax column. That way the only thing getting heated to higher temps on the front would be uncoated guard column.

If you have the room to the left side of the 6890, I would install a small insulated box on the side of the instrument and run the transfer lines out through the openings that are there for a mass spec interface to enter the oven, then just get a heater like one used on the inlets and place it inside the box and attach it to the connector for the AUX heater. Without a fan it will take a while to reach equilibrium, but once it does it should maintain temp quite well.

Just make the box out of some of the foil covered foam insulation and attach it to the GC. I made a box similar to this in graduate school that was heated with a light bulb attached to a thermal controller and it would maintain temps quite well. Just cut the foam to the size needed to make the sides of the box and fasten it together with aluminum duct sealing tape. On the outer side just attach the tape to the rear side of that piece and you have a door you can open to replace the column easily, fasten the opposite edge with a piece of wire or small piece of tape as the latch. Mount to GC with either more tape or some short screws put into it from the inside of the box.

[AICMM]

AZBiodiesel,

1) Use a Hammond box on top of the GC as an aux oven. Since you already have used up your injector heaters you will need an Valve heater and you use that for the aux oven (been there, done that.) The only issue is that the Hammond might not be big enough. Glue in insulation (to the walls and roof, holes for the column inlet and outlet and hole for the heater cartridge.) Left Hand side offers options but in your case heating is going to be an issue.

2) Not a bad idea to buy a proper valve base so that the mass matches that which is expected and the heater will not wander too much.

3) Use a piece of uncoated MXT transfer line from the inlet port to the column to avoid the issue of cooking the xfer line when running triglycerides.

If you want further advice feel free to contact me at aicmm at flash dot net.

Best regards,

aicmm

[AZBiodiesel]

AICMM,

Searching for "valve heater" brought up these guys who seem to have it all figured out already:

http://www.vici.com/act/hce.php

If used in conjunction with this:
http://www.vici.com/gc/column_heating_unit.php

Looks like I could even do EN 14103 ester content externally as well with a nickel plated wax column...