Hide-and-seek: Threshold values and contribution towards better understanding of recovery rate in microplastic research

Abstract

Microplastic pollution has become one of the most pressing environmental issues. A fundamental criterion for risk assessment is the concentration of found microplastic that can be altered during microplastic isolating from the sample. Recovery rate (i.e. positive control) is an important feedback component that identifies accuracy, quality and efficiency of sample processing, same as physical and chemical impact. Here, using 100 µm red polystyrene (PS) beads we have tested some methodological steps that can be responsible for the possible microplastic losses during sample treatment and based on that, we provided a recovery rate threshold values. Our results support that the choice of the extraction method (vacuum filtration versus wet sieving) results in lower recoverability when vacuum filtration is used and that used separatory funnels size versus material amount impacts the efficiency or recoverability in density separation. We have also analysed microplastic recovery rate when different samples treatment steps from widely used isolation protocols (sediment and water) were applied and our results suggest that there are a number of factors affecting recovery rates, of which physical effects (loss by consecutive treatment steps due to material transfer) are more important than possible chemical degradation. Sample filtration method determines recovery rate from < 40 to > 80%. The number of sample processing steps involving transfer has a direct impact on recovery rate. As a measure of quality assurance, recovery rate thresholds are introduced.

Underestimating microplastics? Quantification of the recovery rate of microplastic particles including sampling, sample preparation, subsampling, and detection using µ-Ramanspectroscopy

“…It showed that MPPs with a density higher than water can be sampled from the middle of a water column of a technical and turbulent mixed stream. The recovery rate is higher than the average recovery rate reported by Dimante-Deimantovica et al [1] for an MP analysis protocol with seven transfer steps and comparable particle size (40%, 100 µm). The analysis protocol in this study had eight transfer steps.…”

“…While blanks are important to control sample contamination with ubiquitous MP and to ensure the MP concentration in a sample is not overestimated, recovery rates are important to quantify false-low results. In a review of several research papers, Dimante-Deimantovica [1] showed that the recovery rate of 100-µm microplastic particles (MPPs) ranges between 40 and 80%, decreasing with the number of transfer steps in sample preparation. Other studies show that the recovery rate decreases rapidly with the particle diameter [2][3][4][5].…”

Development of a machine learning-based method for the analysis of microplastics in environmental samples using µ-Raman spectroscopy

“…Especially the single model approach seems to be acceptable, as recall and precision are around 90%. However, we decided to increase precision and recall by using the human-machine teaming approach for several reasons: In spectroscopic microplastic analysis, recovery rates are low [11,29]. Therefore, any possibility to increase accuracy should be taken.…”

Downward migrating microplastics in lake sediments is a tricky indicator for the onset of the Anthropocene

“…the number of sample transfers during sample puri cation affects the recovery rate. Therefore, it can be assumed that the actual MP concentration in the lake sediments might be at least twice or even three times higher 43 . Air background samples and procedural/ eld blanks were analysed in parallel with lake sediment samples and were not considered to change the results signi cantly (see more details in the methods section).…”