Identification of polymer building blocks by Py–GC/MS and MALDI-TOF MS

Metabolomic Analysis of Polymicrobial Wound Infections and an Associated Adhesive Bandage

Concerns about ion suppression, spectral contamination, or interference have led to avoidance of polymers in mass spectrometry (MS)-based metabolomics. This avoidance, however, has left many biochemical fields underexplored, including wounds, which are often treated with adhesive bandages. Here, we found that despite previous concerns, the addition of an adhesive bandage can still result in biologically informative MS data. Initially, a test LC-MS analysis was performed on a mixture of known chemical standards and a polymer bandage extract. Results demonstrated successful removal of many polymer-associated features through a data processing step. Furthermore, the bandage presence did not interfere with metabolite annotation. This method was then implemented in the context of murine surgical wound infections covered with an adhesive bandage and inoculated with Staphylococcus aureus, Pseudomonas aeruginosa, or a 1:1 mix of these pathogens. Metabolites were extracted and analyzed by LC-MS. On the bandage side, we observed a greater impact of infection on the metabolome. Distance analysis showed significant differences between all conditions and demonstrated that coinfected samples were more similar to S. aureus-infected samples compared to P. aeruginosa-infected samples. We also found that coinfection was not merely a summative effect of each monoinfection. Overall, these results represent an expansion of LC-MS-based metabolomics to a novel, previously under-investigated class of samples, leading to actionable biological information.

Polyethylene Glycol-Isophorone Diisocyanate Polyurethane Prepolymers Tailored Using MALDI MS

The reaction of diols with isocyanates, leading to mono-functional and di-functional prepolymers may be investigated using various characterization methods which show the overall conversion of isocyanate monomers. On the other hand, matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) polymer characterization can be employed to identify the monomer units, the end-group functionalities, molecular weight averages, and to determine the copolymer sequence. Herein, we focus on prepolymer synthesis using isophorone diisocyanate (IPDI), a widely used diisocyanate for prepolymers preparation, especially in waterborne polyurethane materials. Thus, the reaction between polyethylene glycol diol and IPDI was in-depth investigated by mass spectrometry to determine the influence of the reaction parameters on the prepolymer's structure. The relative content of the different functional oligomer species at given reaction times was determined in the reaction mixture. More specifically, the offline analysis revealed the influence of reaction parameters such as reaction temperature, the concentration of reactants, and the amount of dibutyltin dilaurate catalyst. The established MALDI MS analysis involved measurements of samples, first, directly collected from the reaction mixture and secondly, following derivatization with methanol. The obtained results revealed the effects of reaction parameters on the functionalization reaction with isocyanates, allowing to achieve a better reaction control.

Single-particle analysis of micro/nanoplastics by SEM-Raman technique

Micro/nanoplastics (MNPs) have received global concern due to their widespread contamination, ingestion in organisms, and the ability to cross the biological barrier. Although MNPs have been detected in a variety of ecosystems, the identification of single MNPs remains an unsolved challenge. Herein, for the first time, scanning electron microscope (SEM) coupled with surface-enhanced Raman spectroscopy (SERS), which combined the advantages of ultrahigh spatial resolution of SEM and structural fingerprint of Raman spectroscopy, was proposed to identify MNPs at single-particle level. Under the optimum conditions, the polystyrene (PS) MNPs with sizes of 500 nm and 1 μm were identified by the image of SEM and fingerprint peaks of Raman spectroscopy. Additionally, the applicability of the method in different sample matrices and for other types of MNPs such as poly-methyl methacrylate (PMMA) with the sizes of 300 nm, 1 μm were validated. This method is simple, rapid and effective and is likely to provide an essential tool to identify other micro/nanoparticles in addition to MNPs.

Chemical Analysis of Microplastics and Nanoplastics: Challenges, Advanced Methods, and Perspectives

Microplastics and nanoplastics have become emerging particulate anthropogenic pollutants and rapidly turned into a field of growing scientific and public interest. These tiny plastic particles are found in the environment all around the globe as well as in drinking water and food, raising concerns about their impacts on the environment and human health. To adequately address these issues, reliable information on the ambient concentrations of microplastics and nanoplastics is needed. However, micro- and nanoplastic particles are extremely complex and diverse in terms of their size, shape, density, polymer type, surface properties, etc. While the particle concentrations in different media can vary by up to 10 orders of magnitude, analysis of such complex samples may resemble searching for a needle in a haystack. This highlights the critical importance of appropriate methods for the chemical identification, quantification, and characterization of microplastics and nanoplastics. The present article reviews advanced methods for the representative mass-based and particle-based analysis of microplastics, with a focus on the sensitivity and lower-size limit for detection. The advantages and limitations of the methods, and their complementarity for the comprehensive characterization of microplastics are discussed. A special attention is paid to the approaches for reliable analysis of nanoplastics. Finally, an outlook for establishing harmonized and standardized methods to analyze these challenging contaminants is presented, and perspectives within and beyond this research field are discussed.

Thermal fragmentation enhanced identification and quantification of polystyrene micro/nanoplastics in complex media

As an emerging field of study, microplastics have drawn tremendous attention, but until now little is known about their fate and impacts in the environment. A critical bottleneck is lack of reliable techniques to identify and quantify microplastics in complex media. Here we present a simple, rapid, and effective method for identification and quantification of micro/nanoplastics (MNPs) based on thermal fragmentation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with polystyrene (PS) particles as a model MNP. The PS MNPs are identified by fingerprint peaks in both low-mass (m/z 90, 104, 128, 130, and 312-318) and high-mass regions (repeated peaks with Δm/z 104 in the m/z range 350-5000), and the quantification is carried out with m/z 315.3. The different ionization behaviors enable the differentiation of MNPs with different molecular weights. Notably, we find that a simple thermal pretreatment at 380 °C can facilitate the fragmentation of PS and significantly enhances the intensities of fingerprint peaks in low-mass regions, yielding a detection limit of 25 ng for PS MNPs. The applicability of the method in different sample matrices and for other types of MNPs such as polyethylene terephthalate (PET) is also validated. Considering the current shortcomings in MNP analysis, this work provides a powerful tool to advance the MNPs research.