Things you can do with a MultiFlex (No.5) – Thermal Extraction

Pixel Kicks

17th December 2013

GERSTEL Thermal Desorption Unit (TDU)

Thermal extraction is another great GC extraction technique which sits within the multi-instrumental talents of the MultiFlex sample preparation system.

Sitting nicely between thermo desorption (from adsorption tubes, like Tenax) and Pyrolysis, thermal extraction satisfies the requirements of the analytical chemist aiming to characterise the volatile and semi-volatile organic profile of complex, high molecular weight sample matrices.

It typically occurs at temperatures anywhere from 50 to 350oC, depending on the application, and allows solvent-free stripping of volatile organics in a clean, sensitive, and efficient manner requiring little or no sample preparation and is solvent-free and thus labour, cost-per-sample and environmentally friendly.

Being selective towards the lower boiling point constituents of your sample means it keeps the high molecular weight non-GC-able material away from your precious columns and detectors. Who doesn’t want this!

Pushing the limits of what’s achievable in terms of recovering higher molecular weight, but still volatile, compounds like phthalates and longer-chain hydrocarbons is something that is less of an issue with the innovative short ‘liner-in-liner’ sample path of the GERSTEL Thermal Desorption Unit (TDU) which forms an integral part of the MultiFlex system.

This short sample path also does wonders for the recovery of ‘active’ compounds that have the potential to, and often do, get lost in long heated transfer lines between the thermal extraction instrumentation and the GC column. Let’s leave the ability to make thing’s disappear to the magicians of this world shall we?

Of course, as with the application of any GC introduction technique, an understanding of not only your target analytes but your sample matrix is important to developing that robust analytical method fit for the purpose it was intended.

In the case of polymers, for example, understanding how these macro-molecules behave at elevated temperatures, for instance as a glassy or amorphous, closed or open-celled structures, is critical to maximising your detection limits and providing an accurate volatile profile, free from extraneous compounds, which might actually be generated as part of the heating process.

In addition, sample homogeneity is also something which needs consideration as the sample sizes are generally quite small. Also if your target analytes are thermally labile or indeed your sample sensitive to elevated temperatures you may need to be careful. Generally neither of these causes any real issues for most applications.

What are we able to achieve? Well, we can use it to reverse engineer materials, determine their solvent composition, their additives and their stabilisers, profile their flavours and theirs fragrances, and determine potential evolution of toxic materials; the list goes on and on…

The versatile and sometimes overlooked technique of thermal extraction can be applied to pretty much any non-volatile material including composites, food, plant material (like tobacco) and of course polymers.

Now here’s the really interesting bit……

The MultiFlex system gives you the ability (with TDU-Pyro option) to perform thermo desorption, thermal extraction and pyrolysis in one system with little or no manipulation of the hardware once and for all bridging the gap for thermal analysis by GC-MS. Now that’s progress!

For more information, please email, or call the office now on 01223 279210.