Dataset Information

Validation of an FT-IR microscopy method for the determination of microplastic particles in surface waters.

ABSTRACT: For analysis of microplastic (MP) particles in aquatic or solid compartments, standardized methods are required, yet data obtained by current methods are of limited comparability. Current methods include Fourier-transform Infrared (FT-IR) microscopy, Raman microscopy or thermo-analytical methods and attempts to compare data-sets from these methods have largely failed. Only little quality data based on validated methods and appropriate quality standards is available. Thus, reports of presence and numbers of MP still vary significantly from each other without a reliable indicator which of the reported data fulfils data acceptable quality requirements. A methodology for the determination of MP via FT-IR microscopy is introduced and critically discussed regarding mandatory validation parameters and applicability. Furthermore, advantages and challenges of this method are put into relation to other spectroscopic and spectrometric techniques.

SUBMITTER: Huppertsberg S

PROVIDER: S-EPMC7168761 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Validation of an FT-IR microscopy method for the determination of microplastic particles in surface waters.

Huppertsberg S S Knepper T P TP

MethodsX 20200321

For analysis of microplastic (MP) particles in aquatic or solid compartments, standardized methods are required, yet data obtained by current methods are of limited comparability. Current methods include Fourier-transform Infrared (FT-IR) microscopy, Raman microscopy or thermo-analytical methods and attempts to compare data-sets from these methods have largely failed. Only little quality data based on validated methods and appropriate quality standards is available. Thus, reports of presence and ...[more]

PMID: 32322543

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Project description:Rat ear cartilage was studied using Fourier transform-infrared (FT-IR) microspectroscopy to expand the current knowledge which has been established for relatively more complex cartilage types. Comparison of the FT-IR spectra of the ear cartilage extracellular matrix (ECM) with published data on articular cartilage, collagen II and 4-chondroitin-sulfate standards, as well as of collagen type I-containing dermal collagen bundles (CBs) with collagen type II, was performed. Ear cartilage ECM glycosaminoglycans (GAGs) were revealed histochemically and as a reduction in ECM FT-IR spectral band heights (1140-820 cm-1) after testicular hyaluronidase digestion. Although ear cartilage is less complex than articular cartilage, it contains ECM components with a macromolecular orientation as revealed using polarization microscopy. Collagen type II and GAGs, which play a structural role in the stereo-arrangement of the ear cartilage, contribute to its FT-IR spectrum. Similar to articular cartilage, ear cartilage showed that proteoglycans add a contribution to the collagen amide I spectral region, a finding that does not recommend this region for collagen type II quantification purposes. In contrast to articular cartilage, the symmetric stretching vibration of -SO3- groups at 1064 cm-1 appeared under-represented in the FT-IR spectral profile of ear cartilage. Because the band corresponding to the asymmetric stretching vibration of -SO3- groups (1236-1225 cm-1) overlapped with that of amide III bands, it is not recommended for evaluation of the -SO3- contribution to the FT-IR spectrum of the ear cartilage ECM. Instead, a peak (or shoulder) at 1027-1016 cm-1 could be better considered for this intent. Amide I/amide II ratios as calculated here and data from the literature suggest that protein complexes of the ear cartilage ECM are arranged with a lower helical conformation compared to pure collagen II. The present results could motivate further studies on this tissue under pathological or experimental states involving ear cartilage.

Project description:Reference materials (RMs) are vital tools in the validation of methods used to detect environmental pollutants. Microplastics, a relatively new environmental pollutant, require a variety of complex approaches to address their presence in environmental samples. Both interlaboratory comparison (ILC) studies and RMs are essential to support the validation of methods used in microplastic analysis. Presented here are results of quality assurance and quality control (QA/QC) performed on two types of candidate microplastic RMs: dissolvable gelatin capsules and soda tablets. These RMs have been used to support numerous international ILC studies in recent years (2019-2022). Dissolvable capsules containing polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), and polystyrene (PS), in different size fractions from 50 to 1000 µm, were produced for one ILC study, obtaining relative standard deviation (RSD) from 0 to 24%. The larger size fraction allowed for manual addition of particles to the capsules, yielding 0% error and 100% recovery during QA/QC. Dissolvable capsules were replaced by soda tablets in subsequent ILC studies and recovery test exercises because they were found to be a more reliable carrier for microplastic RMs. Batches of soda tablets were produced containing different single and multiple polymer mixtures, i.e., PE, PET, PS, PVC, polypropylene (PP), and polycarbonate (PC), with RSD ranging from 8 to 21%. Lastly, soda tablets consisting of a mixture of PE, PVC, and PS (125-355 µm) were produced and used for recovery testing during pretreatment of environmental samples. These had an RSD of 9%. Results showed that soda tablets and capsules containing microplastics >50 µm could be produced with sufficient precision for internal recovery tests and external ILC studies. Further work is required to optimize this method for smaller microplastics (< 50 µm) because variation was found to be too large during QA/QC. Nevertheless, this approach represents a valuable solution addressing many of the challenges associated with validating microplastic analytical methods.

Dataset Information

Validation of an FT-IR microscopy method for the determination of microplastic particles in surface waters.

Publications

Validation of an FT-IR microscopy method for the determination of microplastic particles in surface waters.

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