Multi-Analytical Approach to Characterize the Degradation of Different Types of Microplastics: Identification and Quantification of Released Organic Compounds

Abstract

Microplastics and nanoplastics represent one of the major environmental issues nowadays due to their ubiquitous presence on Earth, and their high potential danger for living systems, ecosystems, and human life. The formation of both microplastics and nanoplastics strongly depends on both the type of pristine materials and the degradation processes related to biological and/or abiotic conditions. The aim of this study is to investigate the effect of two of the most relevant abiotic parameters, namely temperature and light, taken under direct control by using a Solar box, on five types of reference polymers: high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET). A multi-analytical approach was adopted to investigate in detail the first steps of plastics degradation. Samples of plastic materials at different degradation times were analyzed by means of 1H NMR spectroscopy and thermal desorption gas chromatography mass spectrometry (TD-GC-MS) technique. Several minor molecular species released during degradation were consistently identified by both techniques thus providing a comprehensive view of the various degradation products of these five types of microplastics.

Mass Spectrometry Insight for Assessing the Destiny of Plastics in Seawater

“…Another research avenue to be pursued before long is research toward unveiling the structural changes in plastics during degradation as well as the structure of disintegrated fragments. With this goal in mind, we will rely on using a selection of complementary spectroscopic techniques such as Fourier transform IR [ 15 ], laser direct IR [ 38 ] and NMR [ 8 ].…”

“…It is also important to comprehend that the hazard potential of microplastics is not only because of their small size, increased uptake and reactivity [ 6 ], but also arises due to various plastic additives, such as persistent organic pollutants [ 7 ], catalytic remnants, polymerization solvents, etc. [ 8 ], or adsorbed toxic metals, which can leach into seawater and be consumed by marine organisms [ 9 , 10 ].…”

Oxo-Additives for Polyolefin Degradation: Kinetics and Mechanism

“…(6) Thermal properties (crystallinity and temperature of melting) by differential scanning calorimetry (DSC); successive self-nucleation and annealing (SSA). ( 7) Nuclear magnetic resonance (NMR) to characterize the products of the degradation of polymers and microplastic [14]. Such approaches can provide kinetic data to help reveal the mechanism of the process.…”

“…The existing schemes are presented below. These schemes can be classified as initiation reactions (1), (2), reactions where unsaturated compounds participate ( 5), ( 6), ( 7), ( 27), (28), recombination reactions ( 18)-( 22), (30), Norrish I and II reactions (15,16), propagation reactions (4), ( 8), ( 10), ( 23), ( 25), ( 26), ( 29), ( 31)- (33), branching reactions ( 9), ( 17), (24), reactions with singlet oxygen (11), (12), and metal autocatalysis reactions where the metal ion is oxidized (13) or where metal ion reduction takes place (14).…”

“…The fate of key intermediate ROOH can vary: decaying to • OH and RO • (9) or decaying to ketone and macroradical (10). ROOH can also play a role in autooxidation in the presence of metals ( 13), (14); the scheme is considered below). Ketone, e.g., as a product of (10), can absorb a UV photon and be a source of highly reactive singlet oxygen (11).…”