An In Situ Depolymerization and Liquid Chromatography–Tandem Mass Spectrometry Method for Quantifying Polylactic Acid Microplastics in Environmental Samples

Abstract

Polylactic acid (PLA) is the most commonly used biodegradable plastic with rapid growth in recent years. This leads to predictable increased pollution of PLA microplastics (MPs) in the environment. However, quantification methods for the PLA MPs are still lacking. In this study, a method based on alkaliassisted thermal depolymerization and liquid chromatography− tandem mass spectrometry (LC−MS/MS) analysis was developed to quantify PLA MPs. After the background monomer compound was removed, PLA MPs were efficiently depolymerized to lactic acid and detected by LC−MS/MS with a limit of quantification of 18.7 ng/g. The ideal recovery of spiked PLA MPs of 93% was obtained, and the PLA MPs did not need to be separated or extracted in advance from the environmental samples. Using this method, PLA MPs were detected in all the sediment samples of a reservoir at a range of 53.5−491 ng/g dw, and the concentrations decreased with the sediment depth. In addition, after soaking in water at 95 °C for 30 min, approximately 12 μg of PLA MPs was released from a single teabag.

Machine learning driven methodology for enhanced nylon microplastic detection and characterization

“…The observed disparities between our results and those of Busse et al 8 could also potentially be attributed to the use of different types of teabags. The counts/quantities reported by other studies listed are expressed in the mass of MPs released per teabag 11 , 12 , or the number of MP particles per kg of teabags 10 . Therefore, direct comparisons with these studies are not possible in our paper.…”

“…Afrin et al 10 -5 min at 95 °C Particle-based analysis using FTIR spectroscopy 60 MPs/kg of teabags Cella et al 11 Nylon teabag 10 min at 95 °C Mass estimation based on Beer's law and FTIR spectral analysis 1.13 ± 0.07 mg of nano plastics/teabag Wang et al 12 PLA teabag 30 min at 95 °C Depolymerization followed by Liquid Chromatography-Tandem Mass Spectrometry analysis 12 μg of MPs/teabag for example, DFIR imaging is fast yet provides unreliable results while HSI and point spectra measurements allow for accurate results, but they are time-consuming for data collection. With the QCL system integrated within the O-PTIR microscope, the microscope can generate a single frequency IR image of a 480 μm × 640 μm (spatial resolution: 2 μm) area of a filter in approximately 3 min and 20 s. When an appropriate wavenumber and a threshold value are selected, the generated image shows the majority of MP particles while ruling out most non-MP particles.…”

Monitoring Poly(methyl methacrylate) and Polyvinyl Dichloride Micro/Nanoplastics in Water by Direct Solid-Phase Microextraction Coupled to Gas Chromatography–Mass Spectrometry

“…To date, various analytical methods have been developed to detect the MNPs in water samples, such as Fourier transform infrared spectrometry, − Raman spectroscopy, , scanning electron microscopy, thermal analytical methods, − and other techniques. − Among the reported analytical methods, thermal analytical methods (e.g., pyrolysis gas chromatography–mass spectrometry (Py-GC-MS)) enable MNPs to be decomposed into monomer or multimer molecules by thermal treatment and then achieve the determination of MNPs through monitoring the monomers or multimers by GC-MS. Owing to its simple preparation procedures and simultaneous qualitative/quantitative analysis, Py-GC-MS has been a reliable analytical method for determining MNPs in water samples. , …”