Using MALDI-TOF MS imaging and LC-HRMS for the investigation of the degradation of polycaprolactone diol exposed to different wastewater treatments

Abstract

Polymers are used in high amounts in a wide range of applications from biomedicine to industry. Because of the growing awareness of the increasing amounts of plastic wastes in the aquatic environment during recent years, the evaluation of their biodegradability deserves special attention. In the past, most efforts were dedicated to studying the biodegradation of polyesters in soil and compost, while very little research has been conducted on their fate in wastewater. Here, we assessed the ability of bacterial communities residing in the aerobic and denitrification tank from a wastewater treatment plant (WWTP) to degrade the polymeric ester polycaprolactone diol (PCLD; average molecular weight of 1250 Da). Following the incubation of the solid polymer in WWTP tanks, matrixassisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) was used to provide evidence for hydrolytic reactions and to study differences in the spatial degradation on the PCLD surface. It was demonstrated that regardless of the wastewater type, the chemical structure on the PCLD surface underwent modifications after 7 days of exposure.Apart from the parent PCLD peak series in MALDI-MSI mass spectra, the presence of a second oligomer series with mass peaks spaced by m/z 114 (as in PCLD) was observed. It was proposed to correspond to polycaprolactone (PCL) originating from the hydrolytic cleavage of the diethylene glycol from PCLD. Their ion masses were detected at m/z 104 below the PCLD peaks and their structures were proposed as PCL cyclized oligomers. Differences in the spatial distribution of low MW ions (<800) between the aerobic and denitrifying exposed samples in MALDI MSI were also noticeable. While the ions at m/z 221.1, 247.1 and 449.2 predominated in the aerobic exposed sample, those at m/z 475.5 and 677.4 were characteristic of the denitrifying one. The MALDI-MSI measurements in the low mass range were complemented with LC-HRMS analysis to determine plausible structures of the major degradation products. Ten transformation products (TPs) were detected in the denitrifying wastewater experiment, five of them were the result of ester hydrolysis forming caprolactone oligomers (TPs 220, 334, 448, 562, and 676) while the other series corresponded to formation of PCL chain with a terminal diethylene glycol, likewise formed by ester hydrolysis (TPs 246, 360, 474, 588, and 702).

Development of benzimidazole derivatives as efficient matrices for the analysis of acidic small‐molecule compounds using matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry in negative ion mode

“…Matrix‐assisted laser desorption/ionisation (MALDI) is a soft ionisation technique that is widely utilised for mass spectrometric (MS) analysis of various biomolecules, including proteins, 1,2 peptides, 3 oligosaccharides, 4 oligonucleotides, 5 and synthetic polymers 6,7 . Due to its high sensitivity and molecular specificity, MALDI has been the subject of intense and continuous research efforts in fields such as metabolomics, 8,9 clinical medicine, 10,11 phamacology, 12,13 plant sciences 14,15 and environmental sciences 16,17 .…”

New insight into the evaluation of complex mixture biodegradability: an UHPLC-qToF “all-ion MS/MS” acquisition technique for the untargeted and targeted analysis of pharmaceutical formulation biodegradation

“…The ultra-high performance liquid chromatographyquadrupole time-of-flight mass spectrometer (UHPLC-qToF) is a recent type of spectrometer characterized by an ultra-high performance chromatographic separation of the molecular species that has been successfully employed for its fast, highresolution separations, high-resolution mass spectra and high sensitivity. Even if high resolution mass spectrometry as well as other spectroscopic methods were previously reported for the investigation of the environmental impact produced by pharmaceuticals and cosmetic formulations [23][24][25][26] to the best of our knowledge this is the first UHPLC-qToF "all-ions MS/MS" approach to perform metabolites fingerprints by untargeted data treatment of pharmaceutical formulation submitted to a readily biodegradability test and targeted analyses for deeper investigation of the readily biodegradation output.…”

“…Even if high resolution mass spectrometry as well as other spectroscopic methods were previously reported for the investigation of the environmental impact produced by pharmaceuticals and cosmetic formulations, [24][25][26][27][28] to the best of our knowledge, this is the rst UHPLC-qToF "all-ion MS/MS" approach to obtain metabolite ngerprints by untargeted data treatment of pharmaceutical formulation submitted to a ready biodegradability test and targeted analyses for deeper investigation of the readily biodegradation output.…”

A mass spectrometry imaging method for visualizing synthetic polymers by using average molecular weight and dispersity as indices

“…It is also considered to be a powerful tool for synthetic polymers; however, MALDI-MSI in polymer applications is still limited, although the number of reports is increasing. [18][19][20][21][22][23][24][25][26][27] Conventional MALDI-MSI visualizes the spatial distribution of target compounds, which have specified m/z values, by extracting their mass images from the MSI raw data. This method is not suitable for synthetic polymers because they have a mass distribution.…”

“…However, the differences in spatial distribution were discussed in previous reports by comparing the mass images of several degrees of polymerization. [21][22][23]26,27 Kune et al suggested drawing the sum of mass images of chemically related compounds using KMD analysis. 28 They have successfully applied the method to find lipids, tetraalkylammoniums, polymers and lipopeptides in complex imaging mass data.…”