Chromatography Forum

I'm looking at combining P&T (a tekmar LSC 2000) with a GC-MS system (hp 5890 and 5970) to run methanolic extracts. Anyone know of any particuarly good articles, papers, etc. in that area? Specifically dealing with combining the two instruments would be great. Thanks in advance.

I've got two Teledyne-Tekmar HT3 headspace autosamplers on 6890/5973 and 7890/5975 instruments. I didn't have any trouble hooking them up on my own, but Teledyne-Tekmar has always been exceedingly helpful when I've asked questions. You could give them a shout and see what they have to say.

If you have a methanolic extract why not just inject it as a liquid ?

Peter

If you have a methanolic extract why not just inject it as a liquid ?

Peter the original poster says he intends to use Purge and Trap so we might assume that the samples are too dilute to carry out direct injection ? A newer instrument (5970 is not as sensitive as a new MS) and large volume injection would allow direct liquid injection ?

not only that, but I have other plans for the purge and trap beyond methanolic extracts once I can get the combination of the two instruments to work together.

Working with samples in a methanol matrix will actuuly make your life more difficult because the methanol will adversely affect the performance of the trap packing. For a proof of concenpt investigation I would go for aqueous matrices, or even better, dry material. Maybe you could even skip the methanol extraction and purge the samples directly - that way you get maximum benefit out of the purge and trap.

Peter

Hey! I'm trying to attach an Agilent 6890 to a Tekmar LSC 2000 for VOC analysis. I looked at getting an Injection Port "Weldments" for Agilent GCs--Tekmar. anyone knows a cheaper way to go about this?! or any other ideas, please let me know.

cheers,

The most common way to interface the P&T to a GC is to cut the carrier in line close to the injection port, run that line to the P&T, and attach the end of the transer line to the stub of tubing at the injection port weldment. One very important thing is to make sure you cut the carrier in line, not the septum purge line. The tubing is actually two different sizes, the carrier in line is 1/16 inch and the septum purge line is 2 mm. Make sure you cut the smaller diameter tubing.

There are plenty of posts on the forum about problems with plumbing the transfer line from the headspacer into the carrier gas line to the inlet. Rather run the transfer line through the septum port. You might have to by a needle adapter to go on the end of the transfer line, but that will probably be cheaper than a new weldment.

Peter

okay! I chose to cut the GC carrier line, redirect that into the P&T. Now, I noticed the tubing coming out of the P&T is actually a capulary tube and I'm thinking of changing that to a 1/16" inch stainless steel tube such that it would fit the union i have and the GC carrier tubing is also 1/16" inch stainless steel.
what do you think of replacing tubing coming out of P&T to GC from capulary tube to a 1/16" inch, which is going to be a few feet long?! my concerne: is my sample going to be spread out since i'll be using a bigger tubing??!

thanks,

yassir

Use narrow bore SilcoSteel tubing from Restek. That is what OI uses in their purge and trap for the default, and many Tekmar users immediately replace the capillary tubing with the SilcoSteel. You need at least 20 mL/min flow for proper trap desorption, so peak broadening with the steel tubing is not an issue.

How long, do you sugest, the tubing should be from p&t to GC injection port?... just want to be sure we do not sacrifice concentration by using a piece that is too long...

hey! do you have any instructions / recommendations on taking apart the tekmar LSC 2000 and cleaning the 6-port valve. I will be attempting this very soon and any input is greatly appreciated.
thanks,