Analytical pyrolysis – gas chromatography – mass spectrometry (Py-GC/MS) with micro UV-irradiator system

  The system is composed of an EGA/PY-3030D micro-furnace pyrolyzer, equipped with an AS-1020E autosampler, an MJT-1035E liquid nitrogen cryo-trap system, an UV-1047Xe micro UV-irradiator, a QSP-1046E quick-stabilizing pressure flow switch (Frontier Laboratories Ltd., Japan), and a CGS-1050Ex carrier gas selector, interfaced with an 8890 gas chromatograph equipped with a 5977B bundle EI turbo mass spectrometric detector (Agilent Technologies, USA).
Analytical pyrolysis is a micro-destructive technique allowing the characterization of organic materials to be performed by thermally inducing the degradation of the sample under inert atmosphere. The sample is near-instantaneously heated at temperatures in the range 100-800 °C under inert atmosphere. In the range 100-300 °C, desorption/volatilization of the low molecular weight, volatile compounds occurs, while at higher temperatures the thermolysis of chemical bonds also occurs and a mixture of pyrolysis products, known as pyrolyzate, is formed. The pyrolysis products are then directly separated and detected by the GC/MS system. The resulting chromatographic profile – also known as pyrogram – can provide both qualitative and quantitative information on the composition of the original sample.
The technique is particularly powerful in characterizing polymers and macromolecules in general, both natural and synthetic, even in mixtures, in a wide range of molecular weight. Its main advantages are the need for a very small amount of sample (less than 100 μg) and the possibility to perform the analysis on a solid sample, without any pre-treatment. The profiles (comprising both chromatographic and mass spectrometric data) of synthetic polymers along with their additives are available in dedicated libraries, thus allowing the identification of the components of unknown mixtures to be performed automatically.
The purchased instrument constitutes the cutting edge of analytical pyrolysis technology. The pyrolysis is performed with a “drop furnace” system, in which the sample is dropped from an upper zone at room temperature to a lower zone that is pre-heated at the desired pyrolysis temperature. This technology ensures an almost instantaneous heating of the sample, and greatly improves the reproducibility of the resulting pyrograms. The furnace is directly interfaced with the injection port of the GC/MS, minimizing the risk of condensation or secondary degradation of the pyrolyzate during the transfer from the pyrolysis furnace to the chromatographic column.
Analysis set-ups
The combination of the pyrolyzer and the acquired additional instrumentation allows to operate using several instrumental setups:
Instrument equipment
The pyrolysis system is equipped with:
> Micro-furnace Multi-Shot EGA/PY-3030D pyrolyser (FrontierLaboratories Ltd.) available in single-shot, double-shot, evolved gas analysis, and heart-cut (or multi-shot) pyrolysis with AS-1020E autosampler (50 sample slots);
> Micro-jet liquid nitrogen cryo-trap MJT-1035E (Frontier Laboratories Ltd.), that allows the cryo-trapping and focalization of the pyrolysis products;
> MicroUV-irradiator system UV-1047Xe (FrontierLaboratories Ltd.), for the on-line irradiation of samples for studying their ageing and stability, both in air and He atmosphere; QSP-1046E quick-stabilizing pressure flow switch (FrontierLaboratories Ltd.), allowing to quickly switch between air and helium when performing the online UV irradiation;
> CGS-1050Ex carrier gas selector (Frontier Laboratories Ltd.), allowing to switch the carrier gas and perform the pyrolysis under different atmosphere;
> Agilent 8890 gas chromatograph equipped with a mass spectrometric detector Agilent 5977B bundle EI turbo. An additional EI source (EI Extractor) is also available, which provides a further increase in the sensitivity of the system for ultra-trace analysis;
> Search Database and software, including the profiles (comprising both chromatographic and mass spectrometric data) of synthetic polymers along with their additives, allowing the automated identification of the components of unknown mixtures.
Recent applications
Key benefits
By combining the results achieved in the different set-ups, it is possible to obtain complementary information on the target samples. In particular:
> Evolved gas analysis (EGA) is performed by gradually heating the sample while directly connecting the pyrolysis chamber to the mass spectrometer; thus information on the thermal properties of the sample are achieved, along with the average mass spectrum of the products evolved at time intervals;
> Multi-shot (or heart-cut) pyrolysis is fundamental to analyse natural and synthetic polymers in mixtures, also in the presence of additives: flash pyrolysis experiments are performed at different temperatures on the same sample, allowing the GC/MS chromatograms of the pyrolysis product released at each step to be acquired (if the pyrolysis steps are two, then the method is called “double-shot”);
> UV irradiation of the single sample allows an accelerated ageing of the sample to be performed in air or He atmosphere on line, followed by the analysis of the sample by any of the described techniques (EGA, flash or multi-shot pyrolysis).

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