Headspace Transferline to front 6890N inlet w/7683 tower

[MSCHemist]

Hi all I just got my hands on a Tekmar 7000 headspace sampler and am getting ready to install it. I am having trouble figuring out how to get the tranferline close enough to the inlet to minimize the ammount of cold tubing while also not interfering with the 7683 tower. So far the best I can come up with is that the 1/16" carrier line runs on top of the grey plastic top piece and meets the transferline union just in front of the tower. That results in about 15cm of unheated tubing run which I think is too much.

I thought about running it from the front under the grey plastic top cover but it looks like it would intefere with the GC door.

I thought about running it from the back of the GC where the intact carrier line runs but it doesn't look like the transferline with all the insulation will fit as the valley where it emerges it just barely big enough for the line and purge line.

The Lefthand side is blocked by the injector tray.

The right side would require the carrier line to curl arround 180 deg resulting in a long unheated run and probably intefere with opening the inlet to change liners.

Can anyone advise?


My other question is does it make a difference if I use a ZDV union or typical Swagelok 1/16" union?

[Peter Apps]

I would put a needle on the end of the transfer line and go in through the septum. You would need to unclip the injector tower while doing headspace, but that is easy enough as long as the newer hardware is similar to the old ones that I last used.

Peter

[dlbenach]

We have a 7000 to a 6890A. We remove the tower and run the transfer line over the back top cover of the 6890. From the transfer line we go to a 1/16" union and then to the GC inlet. The union is about 3cm and the GC inlet line is about 2 cm. Therefore, there is about 5cm of exposed tubing and union. Our Tekmar service rep recommended buying some insulation and wrapping the exposed section, but we haven't yet. It runs fine for our applications.

[MSCHemist]

Where do you situate the union? If I went over the back of the GC it would half to pass by the rear inlet and the attatchment for the tray would block it. Under the grey cover I don't believe there is enough room. though I haven't taken it apart to check yet.

Tekmar strongly discouraged me using a needle said it would constantly leak. Though my system is interesting in that I have two free auxilary EPC's I can use to control it I could use one for carrier gas and one for vial pressure.

[MSCHemist]

I measured again and I think I can get it down to about 10 cm total with the union and line run if I go in front of the tower. It looks like it would be no better if I went through the grove and into the trench under the center cover.

I'm not thrilled with the length of cold tubing. I'm surprised noone has come up with a solution for this like an adapter that instead of having a needle just replaces the septa and septum nut with a new nut, attached tube and circular gasket arround the protrusion.

[Peter Apps]

I'm surprised noone has come up with a solution for this like an adapter that instead of having a needle just replaces the septa and septum nut with a new nut, attached tube and circular gasket arround the protrusion.

Agilent had the same thought and market it as a "volatiles interface" or something similar. It is basically a low dead volume union cross.

If you not mind doing a bit of bit of plumbing you could try putting a Swagelok 1/16" T on the end of the transfer line (use a soft ferrule so you can get it off again), thread the column in through the opposite port of the T and up into the transfer line by an inch or so, and seal with a vespel/graphite ferrule. Connect the split line to the side port of the T. The connector sits in the oven, which keeps it comfy and warm, and the split point is at the column tip inside the transfer line so there are no dead volumes or cold spots and no contact with bare metal. You can only do this with 0.32 mm or thinner columns, megabores are too fat to go inside the transfer line.

But I cannot see why a transfer line needle through a septum would leak any more than a syringe needle does, unless it is bent to one side in subsequent manipulation of the transfer line to make it fit around things.

Peter

[dlbenach]

Our 7000 is connected to the back inlet so we have a little more room to work with. Looking at it, you should be able to do the same connection to the front. Here's our set up......Facing the GC, the 7000 is to the right of the GC. There are no towers on the GC. We do have the autosampler tray attached. The carrier line that typically goes from the flow control module to the inlet is cut about 2-3 cm from the inlet. You may have to go a little longer to clear the tray connection. A union is attached to this 2-3 cm piece of tubing. Angle it up at about 45 degrees. We bring the transfer line over the back cover and connect it to the union. If you do have to go with a longer piece of tubing you could get some insulatioin from a hardware store to cover it, that's what Tekmar recommends.

[MSCHemist]

Hi dlbenach thanks for your suggestion but I really want both inlets available for the autosampler If I need it. I thought about just keeping the ALS with a db-5 column on the back but I occasionally inject onto the wax column or 1701 on the front.

I will be using a wax column for headspace hence why it needs to be in the front for easy removal when running the higher temp columns in the back.

If I put the 7000 on the right I'd need to either curl the EPC line 180 degrees as it faces the left or run the transferline over or arround the inlet to the left which would make the tower not fit.

I am tempted to go with the needle and just replace septa more often but the needle adapter kit is pretty expensive ~$900.

[MSCHemist]

I spoke with both Agilent and Tekmar and both said no needle. Agilent explained that because the EPC monitors back pressure on the septa purge to control the inlet pressure it gets very confused by the flow coming through the needle and never gets to ready status.

They recommended just wraping insulation tape on the unheated line.

[AICMM]

MSChemist,

Restek has an already chopped inlet weldment if you are interested. PN 22665.

Best regards,

AICMM

[MSCHemist]

Thanks I already chopped it this morning and it will fit under the center cover (barely like stuffing a suitcase). I am going to insulate the heck out of it with cotton and I have some duct foil tape as there is 9cm of line plus the valco ZDV union. So far the MSD and Isopropanol/water check says no leaks and believe me I was sweating bullets though the inlet is taking significantly longer to reach pressure.

Does that mean I need that low flow element in the manual? edit never mind it already has the black one.

Do any third parties sell parts for the 7000? I need a 9 Ml insert, some swell screws, a plastic hinge for the dust cover, and a screw/black post for the dust cover and Tekmar is noncommital as to what they carry as they tell me they don't support it anymore.

[Bigbear]

Been there done that. If you are going to be splitting when using the 7000, I would not worry about any cold spots. I connect a P&T by cutting the supply line to the inlet. The advantage is that the GC's EPC controls the desorb. I split 150:1 so the total flow to the inlet is so fast I can see no loss due to a cold spot.
If you can install the cover over the connection you made the tower can sit there even when you are not using it.

[MSCHemist]

thanks I am probabably going to be either keeping a 10:1 split or pulsing a lower split. Since I hooked up the Tekmar the inlet seems to be having trouble with low flow rates ie splitless. WHen I was getting ready for a pulsed split It shut off the gas saver and shot right up to 40 psi then took 5 minutes to get back down to the appropriate pressure I guess that is because the Tekmar flow element is not meant for flows less than 10ml/min.

I wrapped the union and line with cotton balls and duct foil tape. Hopefully that should keep it at least somewhat warm.

Does anyone besides Tekmar sell parts?
I need to replace some cracked plastic and rubber parts parts (the hinge tabs for the dust cover, one of the dust cover standoffs, the rubber feet at the bottom of the carrusel look bad, and I'd like to get a 9ml insert. I should only need one as I am only going to be heating/shaking one sample at a time.

All that is left is to plumb up the vial pressure gas. I didn't have time last week. I could just use one of my GC's Aux EPC's I have two free or I could just plumb it raw and use the manual controls.

[Peter Apps]

With a back-pressure controlled split splitless inlet the total flow stays the same in both states - it just gets re-routed through different plumbing, so the problem is not likely to be directly flow related.

Peter

[MSCHemist]

Though the Tekmar 7000 has an interchangable flow element I assume that consists of a porous metal frit that provides flow resistance. Or it could be just the large volume of space between the EPC module and inlet. But the EPC is having trouble establishing a flow/pressure <10 ml/min.