When we're analysing triethylamine content by HSGC method using DB-624 in PE Totalchrom, we're facing carry-over problem after each injection.
I welcome the suggestions/alternate procedure for ananlysis.

You have active sites in your transfer lines of whatever HS system you are using or in the column itself.

You may write me privately concerning the details for advice if you wish. I have performed TEA Hydrochloride and TEA-TFA salt analysis with linearity values of 0.999 at low [<100ppm] levels.

chromatographer1 at America On Line.

To March 15 Anonymous,
Why not share your advice in the forum with everyone, I thought that was what this forum was all about?

Regards,
Mark

The problems are closely related to manufacturer's equipment and I don't want to slam anyone's company here publicly.

Chromatographer1

To "Chromatographer1". I don't think it would be considered a slam if you can advise us how to deal with the idiosyncrasies of a particular instrument. None of them are perfect.

I suggest to use a transfer line, sample loop... , made of silco steel material. This necessary to minimize the active places. We use a Tekmar headspace autosampler "silco steel" version.

I recently experienced the exact same problem. I was actually validating an OVI method where one of the OVIs was TEA. Our lab had just switched the transfer tubing on our GCHS systems from fused silica to stainless steel. During the development process, we saw no TEA carryover. Afterwards the transfer tubing was switched and when I began the validation all of the sudden I was seeing several injections worth of TEA carrryover. This method also uses a DB-624 column and we ran it on a P.E HS 40-XL system. I talked to a representative from Restek and he told me more or less what this gentleman has said, and that is that the TEA was probably adsorbing to sites on the stainless steel transfer line or perhaps our injection liner, which strangely enough uses deactivated glass wool. He recommended that we switch to silco-steel transfer lines but unfortunately he could not provide me with any concrete literature that I could reference to explain to our client why we were seeing this carryover. If anyone knows of such literature, that would be extremely helpful to me. Anything at all that might discuss the interaction between tertiary amines and stainless steel.

Since I can limit my discussion to the XL-40....

You should not be using metal transfer lines with this system. You should use FSOT or FS coated metal tubing from Restek, Alltech, Supelco, Entech etc. The column can be placed within the transfer line almost up to the vial itself in the XL-40.

During the process of HS analysis, heating samples of different composition can produce aerosols or vapors that will elute from the sample/dissolution solvent and deposit on the heated transfer line/GC column. Some of these deposits will slowly oxidize from the air injections of the HS sampling of the vials. These will produce acidic sites for TEA free base to complex and adsorb and give your variable carryover recoveries of TEA. This is one cause why a system may initially work with standards and then fail with samples, but not the only one.

This process is more rapid with transfer lines that can catalyze or oxidize these reactions...ie metal.

Using glass or FS deactivated metal lines slow this process. They can be cleansed with solvents on a routine basis if needed. Much of this will depend upon the nature of the materials upon which you perform HS.

Of course to measure low levels you must convert the TEA salt into the free base as quantitatively as possible. Different techniques can be used to achieve this goal, again, this is usually sample related.

These are some of the problems associated with TEA analysis.

Chromatographer1

thank you Chromatographer
vijay