This introduction assumes the reader has skills and experiences in GC and GC/MS analysis or, having no or limited experiences in pyrolysis-GC (Py-GC), is willing to learn and use it in the future.
3.1 Configuration of pyrolysis-GC/MS system
The configuration of a pyrolysis-GC/MS system is shown in Fig. 6.
The analytical system is composed of pyrolyzer, GC, and MS or other detector. The pyrolyzer decomposes a polymer into smaller molecules, and these molecules are separated by GC, and each molecule separated is detected by MS, giving a pyrogram.
A pyrogram is displayed as total ion chromatogram (TIC) obtained from the sum of all the ions detected by MS or extracted ion chromatogram (EIC) obtained from ions having a particular mass. Pyrogram data contains mass spectra that reflect the chemical structure of each molecule; therefore, each of the molecules (pyrolyzates) can be identified using a mass spectral library.
3.2 Three types of pyrolyzers
Pyrolyzers can be categorized into three groups.
Filament type pyrolyzer heats a sample tube with a filament; induction type pyrolyzer heats a sample foil by high-frequency magnetic field; and furnace type pyrolyzer heats a sample by dropping a sample cup to a heated furnace.
The filament type has a drawback in temperature accuracy and moreover, a sample may not be uniformly heated, leading to poor reproducibility. Further, high boiling compounds may be absorbed in the transfer line that conveys the pyrolyzates to GC, making it difficult to introduce high boiling compounds to a GC column.
The induction type should theoretically have a high furnace temperature accuracy; however, a sample cannot be ramp-heated as required for EGA-MS analysis. Further, the way the sample is wrapped with a metal alloy foil can vary and this leads to poor reproducibilities.
Frontier Labs pyrolyzer is a furnace type pyrolyzer in which a sample in a sample cup is dropped (free fall) into a preheated furnace. It has the following advantages over other types:
- Features accurate furnace set temperature in a broad temperature range or continuous ramp-up heating.
- Can be directly interfaced to GC injector, allowing the complete introduction of low to high molecular weight compounds to GC.
- A sample is simply placed in a sample cup and ready for analysis.
3.3 Sample preparation for pyrolysis-GC/MS
Steps from sampling to analysis as described here are simplified when using a furnace type pyrolyzer.
- Step 1：Sampling - materials in different forms can be sampled in a variety of methods.
- Step 2：Placing sample to sample cup - 0.1 to 1 mg of a sample is normally placed in a sample cup.
- Step 3：Loading sample cup to pyrolyzer - load the sample cup into pyrolyzer for GC/MS analysis.