Polymer characterization by GC/MS coupling

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

The compounds analyzed by this technique range from small organic molecules to macromolecules. The disadvantage of the latter lies in the method used to introduce the sample into the mass spectrometer. As the role and choice of sample introduction technique are essential for the analysis of polymers by gas chromatography coupled to MS, this article focuses on this choice and the use of associated techniques.

In most cases, MS requires vaporization of the molecules in their initial form, in order 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), pyrolysis (PY), identification of solid/liquid extraction products, etc., the structure of polymers can be correctly identified by this method.

At present, although other techniques such as MS coupled with liquid chromatography separation methods are being developed, other problems arise in the use of these techniques, such as interfacing between the different equipment, and require the development of new databases for determining the structures of organic molecules. These new analysis 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 this article, we describe the benefits of combining gas chromatography (GC) and mass spectrometry detection in polymer analysis and characterization, detailing the techniques for introducing polymers so that their identification and structure can be traced.

After first describing the various techniques available for introducing a polymer into a mass spectrometer, we go on to discuss the different methodologies that can be used to characterize the basic constituents of polymers, then those that can be used to identify their structure after implementation, trying to trace back the polymerization mechanisms that may have been involved. Finally, we look at the possibilities offered by this technique for characterizing the ageing of materials and identifying the products formed during...