Tekmar LSC 2000 Purge and Trap to 6890-5975.

[MSCHemist]

Hi all

I have an old Tekmar LSC 2000 sitting arround in my lab and I am considering if I could interface to to one of the inlets on my 6890-5975 MS and aquiring the 16 sample autosampler for it so I can do some headspace analysis. The LSC 2000 has a remote cable for a 5890 but also RS-232 communications. Is it possible to hook it up to a 6890's RS232 port and have them able to coordinate a run start?

As for the plumbing itself I am a bit lost as I have boxes of connectors and small parts. I believe I heard someone mention you can get a needle adpater so the transferline goes through the septa rather than hacking up the inlet lines and routing them through the P&T. Is that correct?

Does anyone have a good source to help me get started I am looking to be able to do some headspace sampling and right now manual SPME is all I have.

[AIM]

We put a 2000 on a 6890N system not long ago. You will need to get a special cable from Tekmar.

Tekmar 2000 to 6890N interface cable #14-6689-186
$217

I do have a nice inventory of Tekmar 7000 headspace samplers available right now. They will be completely refurbished and tested with a 6 month warranty.

[Bigbear]

You can use a needle on the end of your transfer line, but I feel cutting the supply line to the inlet is best. Thet way the gc inlet EPC is in control. When you choose to remove the LSC you only need to connect the cuts with a union.

[Peter Apps]

Sorry Bigbear, I have to disagree about plumbing into the inlet carrier feed line. It creates a cold spot with bare metal surfaces right in the sample path, and interposes all the headspacer plumbing between the EPC and the inlet.

I far prefer the needle option, or even better a direct connection to the column, with a much smaller loop than the 1 or 2 ml factory defaults that still seem to be stuck in the age of packed columns.

Peter

[MSCHemist]

I'm just looking for the best option to get some affordable headspace autosampler capacity. If I had the funds I'd get a Gerstell MPS 2 or similar. All I have now is manual SPME which is ok for some flavor TIC's but I ran a residual ethanol last week with std addition and now I am running a lipid oxidation products with analytes all the way up to decadienal and doing the calibration standards and samples all precisely times and overlapping is tricky and keeps me in the lab all day which is a pain.

Purge and trap is best for the very volatiles and volatiles through 1100 Kovats or so correct?

Everytime I look at the LSC 2000 I get bewildered as I have boxes of small parts, tubes and connectors.

[Peter Apps]

The MW range for purge and trap depends to a large extent on what you have in the trap - strong adsorbents like carbons are good for the volatile volatiles but heavy molecules stick to them irrevocably, weaker adsorbents will let the small molecules through, but will trap and release the heavy ones efficiently. Multi-bed traps with layers of progressively stronger adsorbents in the direction of sampling gas flow increase the MW range for a given trap.

Ignore what I said about the direct column connection and smaller loop - I was in equilibrium mode.

Peter

[Bigbear]

Sorry Peter, but I have years of experience with P&T with the inlet modification. Yes there may be a cold spot (in my case < 8 cm and wrapped in insulation) but a total flow of 99 cc/min through a 1/16" line does not allow for any appreciable condensation of sample. I run EPA 524.2 and my MDL's are all < 0.5 ppb.

[MSCHemist]

I was looking at a pic of the Tekmar 2016 autosampler and it looks like a bunch of exposed sparging needles. Are the samples in that thing heated? If not then it is probably a waste of time.

[James_Ball]

I was looking at a pic of the Tekmar 2016 autosampler and it looks like a bunch of exposed sparging needles. Are the samples in that thing heated? If not then it is probably a waste of time.

There is a heater unit that mounts below the 2016 with pocket heaters for the individual sparge tubes. You would need that along with the 2016 to do heated purges. The 2016 came with two types of sparge tubes, the U shaped one with the 1/2" opening that are either fritted or fritless, and the test tube type with 3/4" openings that have a glass tube extending down into the tube for the purge gas to flow through. The testtube type are better for analyzing solid samples(much easier to clean the solid sample out of) and the U shaped ones are better for liquid samples.

As stated above you do need a special cable to hook it up to a 6890. It should attach to the 6890 and the remote between the 6890 and the mass spec, the 2000 doesn't hook directly to the ms if I remember. The dip switches will probably have to be changed too to get all the communications working correctly, but once you get it all figured out the 2000 should work like a dream. I don't think I ever had any real problems with one of those, just became too difficult to get parts if you needed them. Honestly we just got rid of our last one a few years ago.

[MSCHemist]

So it looks like my options are

Obtain the cable, ALS, and pocket heater for the LSC2000 and I'd probably have to hire someone to install it all as I am just not at all familiar with it. So that would probably end up being about $5k. I also have the cryofocusing unit for it.

Buy a more modern P&T system most of the refurbs I've seen seem to be in the range $7-11k. BTW how effective are P&T's without cryofocusing as I am not sure I want to start messing with liquid nitrogen. BTW AIM how much are your 7000's?

Or get an all purpose/SPME autosampler which I am looking at a refurb Combi Pal for ~$15-20k.

So far the main headspace applications I am doing are residual ethanol [We've been selling a lot of islamic compliant flavors lately and IANA has been demanding residual ethanols]. Lipid Oxidation products, and general flavor scans which I can do manually as it isn't that much trouble.

Never mind I see that without cryo one has to operate at a 40:1 split due to the purge flow. That still should be enough sensativity for me as I have an old method that was able to do 1ppm in scan mode under these conditions. With SIM mode I can probably still be well in the hundred ppb range at least.

BTW thanks very much for all your suggestions and assistance.

[James_Ball]

I never used a cryo module before so yes you can get by without it. The way most people hook them up is to cut the gas line for the column flow a few inches before the inlet on the GC. You hook that to a line that goes to the "in from GC" connector on the LSC, then the transfer line from the GC is connected to the stub left on the inlet. Just make sure you cut the incoming gas line and not the septum purge line. For your application you could probably even run higher than 40:1 split and have enough sensitivity for ethanol. From a water matrix I could easily get 100ppb, if you are just doing a headspace over to the trap with no water covering it you may be able to get even better sensitivity.

If you have the manuals hooking them up isn't too bad, as most of the old Tekmar manuals had good well labeled photos of how things went together. I may even still have those manuals here somewhere if you have questions about it.

[MSCHemist]

I'm not so much concerned about hooking up the gas as the sparging tubes the aparatus on the front with the black valves, interfacing it to the instrument, setting up samples and the sequence and that is assuming I can get the ALS and pocket heater and all the sparging glassware.

As for water almost all my samples have an encapsulation that need water to break it so all my samples are either in aques or in soybean oil, propylene glycol, neobee, or triacetin.

I'm leaning towards getting a EST Flex or Combi-PAL. I can get one for $15-20k so I can do SPME or static headspace for ethanol.

Most flavors lab and practically every paper published on it in the last 10 years is SPME vs P&T. I understand despite its flaws with matrix effect it is more reproducible than P&T?

[James_Ball]

For a water soluble compound like ethanol I can see SPME being more reproducible since the equilibrium partial pressures will be constants. For purge and trap ethanol, methanol, and even Acetone can give problems with purging. Things like Benzene work well with purge and trap since they more completely purge from the water.

[Bigbear]

Static head space will also work. It's the one used for blood ethanol.

[sscheib]

Hi!

Your LSC 2000 can be connected to a 6890/5975 GC/MS system. As someone else noted, you will need to purchase the correct interface cable. Part number is 14-6689-186 and has a list price of $217.00. This cable will come with instructions on how to set the dipswitches on the GC/IO board in the LSC 2000 for correct communication.

As for the plumbing connections, it is generally interfaced with a union by cutting into the carrier line of the GC inlet. We do have septum needle adapters available (connect via needle directly into inlet), but these are more widely used with older headspace units and not purge and traps. Also, with the EPC control of a newer GC, it is not recommended. If you still would like to go this route, you will need part number 14-4913-253. This is a septum needle adapter kit for an Agilent GC with a capillary column. List price is $848.00.

It sounds if you may have a headspace application instead of purge and trap. I would be more than happy to have a sale rep contact you regarding an upgrade of your unit to a newer system if you like.

Both the LSC 2000 and 2016 Autosampler are obsolete units and no additional parts are available if you should need them.

Please feel free to contact me directly if you have any additional questions at tekmarsupport@teledyne.com.

Susan Scheib
Sr. Technical Support Specialist
Teledyne Tekmar