3:30 PM - 5:00 PM
[MIS17-P09] Improvement of methodological issues related to quantitative analysis of small microplastics in organisms using infrared spectroscopy
★Invited Papers
Keywords:Small microplastics, Chemical pretreatment, Methodology, Efficiency, Harmonization
Introduction
Theoretically, microplastics (MPs) contaminate the aquatic environment worldwide and are thought to be the cause of the uptake of MPs by aquatic organisms. To elucidate the actual situation, it is necessary to analyze a large number of samples, hence, an efficient evaluation method is required. The Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) defines MPs with a particle size of 10-100 µm as “small MPs (S-MPs)", highlighting the difficulty of detection techniques.
There are two issues in the analysis of S-MPs in vivo using infrared spectroscopy: The first is the uniformity in pretreatment processes. Current methods are tailored to each biological sample, making it difficult to ensure objectivity and quantitative comparisons of results due to differences in accuracy and reproducibility. The second is the efficacy in preprocessing the samples. In MPs analysis with microscopic FTIR, the sample measurement time depends on the efficacy of organic materials (OMs) decomposition in the pretreatment stage. Thus, there is a need to improve the OMs removal capability to eliminate the bottleneck in MPs analysis.
We have developed a pretreatment method to achieve both uniformity and efficacy of S-MPs analysis in organisms. First, the revision of existing pretreatment methods was conducted, followed by the creation of a dedicated reaction vessel. Second, the reproducibility and efficacy of the developed pretreatment method were clarified. Lastly, sediments, algae, and nine fauna species from a tidal flat ecosystem in Tokyo Bay were used as models of the coastal ecosystem, and the versatility of the method was evaluated.
Methodology
Determination of pretreatment method: A pretreatment process including a total of nine steps, which includes three filtrations, was created. To prevent sample loss due to the transfer of containers in the pretreatment process, a "Cylindrical MPs extractor (patent pending)" made out of fluoroplastic was developed.
Verification of reproducibility and efficacy using model materials: Physical loss was verified by comparing the number of particles before and after the reaction using artificial spherical polystyrene particles. Verification of particle breakdown by chemical treatment was conducted by comparing particle shape indices before and after the reaction using three polymer types of particles. OMs degradation efficacy was verified using minced mullet Mugil cephalus and stem powder of reed Phragmites communis collected from the Tsurumi River estuary tidal flat.
Evaluation of versatility using samples from the natural environment: Samples were collected at the tidal flat at the mouth of the Tsurumi River. MPs were measured using the method described above to confirm that the degradation status of biogenic substances was at a level that did not interfere with MPs detection.
Results & Discussion
The impact of this method on MPs is minimal, and it was determined that this method can effectively detect MPs in the aquatic environment. The overall average OMs residue was about 60 % more efficient than the highest efficacy of the previous methods. The results obtained using this method in wild samples confirmed good structural breakdown in 10 specimens, except barnacles, confirming that S-MPs could be reliably measured. The method could not be applied, at first, on barnacles because of the risk that large exoskeletons would remain. However, the method was improved by adding a calcium-chelating agent that dissolved the exoskeletons and enabled the measurement of S-MPs. From the above statement, it was concluded that the pretreatment method including the calcium chelating agent developed in this study succeeded in unifying and improving the efficacy of MPs analysis in coastal ecosystems.
Theoretically, microplastics (MPs) contaminate the aquatic environment worldwide and are thought to be the cause of the uptake of MPs by aquatic organisms. To elucidate the actual situation, it is necessary to analyze a large number of samples, hence, an efficient evaluation method is required. The Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) defines MPs with a particle size of 10-100 µm as “small MPs (S-MPs)", highlighting the difficulty of detection techniques.
There are two issues in the analysis of S-MPs in vivo using infrared spectroscopy: The first is the uniformity in pretreatment processes. Current methods are tailored to each biological sample, making it difficult to ensure objectivity and quantitative comparisons of results due to differences in accuracy and reproducibility. The second is the efficacy in preprocessing the samples. In MPs analysis with microscopic FTIR, the sample measurement time depends on the efficacy of organic materials (OMs) decomposition in the pretreatment stage. Thus, there is a need to improve the OMs removal capability to eliminate the bottleneck in MPs analysis.
We have developed a pretreatment method to achieve both uniformity and efficacy of S-MPs analysis in organisms. First, the revision of existing pretreatment methods was conducted, followed by the creation of a dedicated reaction vessel. Second, the reproducibility and efficacy of the developed pretreatment method were clarified. Lastly, sediments, algae, and nine fauna species from a tidal flat ecosystem in Tokyo Bay were used as models of the coastal ecosystem, and the versatility of the method was evaluated.
Methodology
Determination of pretreatment method: A pretreatment process including a total of nine steps, which includes three filtrations, was created. To prevent sample loss due to the transfer of containers in the pretreatment process, a "Cylindrical MPs extractor (patent pending)" made out of fluoroplastic was developed.
Verification of reproducibility and efficacy using model materials: Physical loss was verified by comparing the number of particles before and after the reaction using artificial spherical polystyrene particles. Verification of particle breakdown by chemical treatment was conducted by comparing particle shape indices before and after the reaction using three polymer types of particles. OMs degradation efficacy was verified using minced mullet Mugil cephalus and stem powder of reed Phragmites communis collected from the Tsurumi River estuary tidal flat.
Evaluation of versatility using samples from the natural environment: Samples were collected at the tidal flat at the mouth of the Tsurumi River. MPs were measured using the method described above to confirm that the degradation status of biogenic substances was at a level that did not interfere with MPs detection.
Results & Discussion
The impact of this method on MPs is minimal, and it was determined that this method can effectively detect MPs in the aquatic environment. The overall average OMs residue was about 60 % more efficient than the highest efficacy of the previous methods. The results obtained using this method in wild samples confirmed good structural breakdown in 10 specimens, except barnacles, confirming that S-MPs could be reliably measured. The method could not be applied, at first, on barnacles because of the risk that large exoskeletons would remain. However, the method was improved by adding a calcium-chelating agent that dissolved the exoskeletons and enabled the measurement of S-MPs. From the above statement, it was concluded that the pretreatment method including the calcium chelating agent developed in this study succeeded in unifying and improving the efficacy of MPs analysis in coastal ecosystems.