Mass spectrometry investigation into the oxidative degradation of poly(ethylene glycol)

Poly(ethylene glycol) (PEG) is an inexpensive, commercially available polymer that has many biomedical and material applications. Due to its water-solubility and biocompatibility, it has been used in drug conjugation, as a humectant, as an anti-foaming agent in food, and as a stabilizer for preservation of antique wooden objects. Despite the robust applications of PEG, the products of oxidative degradation are not fully understood. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the end groups of PEG oxidative degradation products can be proposed. Confirmation of the proposed end groups can be corroborated via selective functionalization reactions as well as electrospray ionization (ESI) tandem mass spectrometry (MS2). Furthermore, the oxidative degradation mechanism of PEG is described here by examining the degradative products using these aforementioned techniques. These findings suggest consistent oxidative behavior for both narrowly dispersed and monodisperse PEG. However, examination of monodisperse PEG allowed for the elucidation of certain degradation behavior due to the presence of a single starting peak, rather than a distribution of peaks, as found in narrowly dispersed PEG. These results demonstrate that MALDI-TOF MS, ESI MS2, and selective functionalization reactions can be applied to the elucidation of polymer end groups and aid in identifying degradation mechanisms.