Automated Thermal Desorption - GC/MS

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Hi everyone!

I am currently working on my bachelor degree project that is about optimizing and evaluating Automated Thermal Desorption coupled online to GC/MS for determination of chemicals in textiles. The instrument is a PerkinElmer Turbomatrix 350 ATD- GC/MS.

The idea is that a small piece of textile can be cut out and directly inserted into the stainless steel tubes- plugged with a metal spring. This is then thermally desorbed in the ATD - using two stage desorption with a cryotrap that goes down to -40 degrees and then rapidly up to 300 deg.

The compounds I am currently interested in are quinoline and its derivatives.
My problem is that the peaks in the mass chromatogram from the quinolines are very low and accordning to previous analysis of the same textile, the intensity of these peaks should be much higher.

Has anyone worked with ATD for thermally desorbing volatiles from solid materials? Do you think the problem is that the analytes are not desorbed from the matrix or that these are trapped in the coldtrap?

My current parameters are set on:
Desorption temp: 150 degrees
Desportion time: 5-20min
Desorption volume: 60 ml/min
Trap temp: -10 - 300 degrees
Outlet split : 1-2 ml/min

Thankful for all the help!
I'm thinking 150 °C it too cool. The boiling point at atmospheric pressure for quinoline is 237 °C. Additionally, you must keep in mind that you have to overcome any intermolecular forces that might be holding the quinoline in the matrix.

Does your textile decompose at 250 °C? The bad thing about going hotter is that you'll start seeing a lot more stuff. It may greatly complicate your chromatography. You might also try to run a sample with a desorb temp. set at 160, 170, 180 (etc.) °C so get the happy medium between complicated chromatography and detection limit. If you're just analyzing the same textile over and over, the matrix will always be the same and thus if your extraction conditions are the same each time, all samples will always be treated equivalently.

If you're looking at different textiles, you might want to find the conditions that work for the most difficult matrix to extract, and use that for all samples.

Good luck. If I had some quinoline in our chemical database, I'd try a couple of things but that's one material we don't have.
Hello, thank you for your answer!

I am currently trying to increase the temperature (180 degrees) to see if it helps, thanks for the tip!

The problem is that one year ago, the same socks that I am analyzing today showed high levels of quinolines when looking at the mass chromatogram. The previous experiments were conducted at 150 degrees with the same parameters as I am using. The only thing I don't know is what split-ratio the previous person used.

It seems that for each experiment I am running (with a new piece of textile from the same sock) the peaks from the quinolines decrease and sometimes they don't appear at all. The question is, where are the compounds? My theories are that they are too retained in the cold trap or that they are slowly evaporating from the sock (it's almost 2 years old).

Best, Sara
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