Structural analysis of polymers using GC/MS coupling

Capillary column gas chromatography (GC) is a method for separating compounds that can be vaporized by heating without decomposition. It involves migrating the components of a mixture through a column, by thermally modifying the affinity ratio of the products to be separated between the column's stationary phase and the carrier gas.

Mass spectrometry (MS) is used to analyze a wide range of samples. Its high sensitivity, combined with its high selectivity and specificity, has made it an extremely powerful analytical technique for the structural characterization of organic molecules over the last thirty years.

The combination of a separation method (GC) with a highly sensitive detector (MS) has led to a high-performance analysis technique for identifying organic molecules.

Compounds analyzed by MS range from small organic molecules to macromolecules. The difficulty, in the case of the latter samples, lies in the choice of techniques to be employed for their introduction into the mass spectrometer, which will be described at length in this article.

In most cases, MS requires vaporization of the molecules in their initial form to acquire a mass spectrum representative of the molecule to be analyzed. This poses a crucial problem, as polymers degrade thermally before vaporization. Despite this limitation and the complexity of the mass spectra obtained, MS plays an important role in the structural analysis of polymers. Using specific, well-controlled introduction techniques such as thermogravimetric analysis (TGA) and pyrolysis (PY), the structure of polymers can be correctly identified by this method.

At present, although other techniques such as MS coupled with liquid chromatography separation techniques are being developed, other problems arise in the use of these techniques, such as interfacing between different equipment, and require the development of new databases for determining the structures of organic molecules. These new analytical techniques will be used primarily for the analysis of biopolymers, which are highly sensitive to temperature rise. The analysis of these biopolymers will not be covered in this article, which will be limited to the analysis of elastomeric, thermoplastic or thermosetting polymers.

In what follows, after a brief presentation of the operating principles of the equipment used, we will describe the advantages of combining gas chromatography (GC) and mass spectrometry detection in the analysis and characterization of polymers, detailing the techniques for introducing polymers into a mass spectrometer. Next, we'll look at the different methodologies that can be used to characterize the basic constituents of polymers, followed by those that...