Analysis of Thermoplastic Copolymers by Mild Thermal Degradation Coupled to Ion Mobility Mass Spectrometry

Abstract

Thermal desorption/degradation with an atmospheric solids analysis probe (ASAP) and ion mobility (IM) separation are coupled with mass spectrometry (MS) analysis and tandem mass spectrometry (MS/MS) fragmentation to characterize thermoplastic elastomers. The compounds investigated, which are used in the manufacture of a wide variety of packaging materials, are mainly composed of thermoplastic copolymers, but also contain additional chemicals (“additives”), like antioxidants and UV stabilizers, for enhancement of their properties or protection from degradation. The traditional method for analyzing such complex mixtures is vacuum pyrolysis followed by electron or chemical ionization mass spectrometry, often after gas chromatography separation. Here, an alternative, faster approach, involving mild degradation at atmospheric pressure (ASAP) and subsequent characterization of the desorbates and pyrolyzates by IM‐MS, and if needed, MS/MS is presented. Such multidimensional dispersion considerably simplifies the resulting spectra, permitting the conclusive separation, characterization, and classification of the multicomponent materials examined.

Applications of ambient ionization mass spectrometry in 2022: An annual review

“…The field of polymer chemistry has not seen many applications of AIMS, however, in recent months, the potential power of rapid analysis is becoming apparent. A recent study coupled ASAP with IMS and tandem MS to study thermoplastic elastomers, a type of copolymer with various industrial uses 158 . Given the complexity of these materials and the high molecular weight of the polymers, traditional analysis has been challenging and time‐consuming.…”

Mass spectrometry of polymers: A tutorial review

“…The desorbed neutral molecules and thermal degradation products are ionized in situ by APCI and sent to the mass analyzer for m/z measurement and identification. The N 2 nebulizing gas and water moisture in the ASAP source give rise to N 2 +• and (H 2 O) n H + reagent ions that ionize desorbates and degradants via charge exchange (to M +• ) and protonation (to [M + H] + ), respectively (Alawani et al, 2022;Endres et al, 2021). ASAP-MS has been used in a variety of analyses, including the characterization of lipids (Pizzo et al, 2022), pesticides and agricultural pharmaceuticals in food (Fussell et al, 2010), particulate matter in vehicular engines (Snyder & Wesdemiotis, 2021), and synthetic polymers and polymer additives (Fouquet et al, 2015; Lebeau & Ferry, 2015;Smith et al, 2012;Trimpin et al, 2009).…”

“…For ASAP-MS studies of polymeric materials, a borosilicate melt point capillary is often used as a substrate for solid or liquid polymeric materials to adhere. This can be accomplished by rubbing the glass capillary onto the analyte material, dissolving the material in a suitable solvent followed by dipping the glass capillary into the solution and allowing the solvent to evaporate (Trimpin et al, 2009), or melting the material, dipping the capillary into the melted sample, and allowing it to cool to room temperature (Alawani et al, 2022). ASAP tolerates a wide range of sample concentrations, as shown with the detection of metabolites at the ng/mL level (Zydel et al, 2012).…”

“…The desorbed neutral molecules and thermal degradation products are ionized in situ by APCI and sent to the mass analyzer for m/z measurement and identification. The N 2 nebulizing gas and water moisture in the ASAP source give rise to N 2 +• and (H 2 O) n H + reagent ions that ionize desorbates and degradants via charge exchange (to M +• ) and protonation (to [M + H] + ), respectively (Alawani et al, 2022; Endres et al, 2021).…”

“…The analytical information gained by ASAP is significantly enhanced if this ionization method is interfaced with ion mobility MS (IM‐MS), which will be discussed under multidimensional MS techniques (vide infra). The ASAP‐IM‐MS approach has been successfully used to characterize lubricants (Barrère, Hubert‐Roux, et al, 2014), polymers and polymer blends (Barrère, Selmi, et al, 2012, 2014), heavy petroleum fractions (Farenc et al, 2016), hydrogels (Endres et al, 2021), and thermoplastic elastomers (Alawani et al, 2022).…”