Science Inventory

Patterns of microparticles in blank samples: A study to inform best practices for microplastic analysis

Citation:

Munno, K., A. Lusher, E. Minor, A. Gray, K. Ho, J. Hankett, C. Lee, S. Primpke, R. McNeish, C. Wong, AND C. Rochman. Patterns of microparticles in blank samples: A study to inform best practices for microplastic analysis. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 333(August 2023):138883, (2023). https://doi.org/10.1016/j.chemosphere.2023.138883

Impact/Purpose:

This article discusses the technical problems associated with microplastic extraction from complex natural matrices with respect to blank contamination. It highlights best practices and accepted procedures to prevent blank contamination. It quantifies general laboratory blank contamination from 12 participating round robin laboratories. This research is critical to advance the field of microplastic analyses as plastic contamination is ubiquitous and to a large extent unavoidable. Overall, this article gives scientists and managers an idea of expectations of laboratory blank contamination with recommendations for quantification for other blanks (field blanks, matrix blanks).

Description:

Quality assurance and quality control (QA/QC) techniques are critical to analytical chemistry, and thus the analysis of microplastics. Procedural blanks are a key component of QA/QC for quantifying and characterizing background contamination. Although procedural blanks are becoming increasingly common in microplastics research, how researchers acquire a blank and report and/or use blank contamination data varies. Here, we use the results of laboratory procedural blanks from a method evaluation study to inform QA/QC procedures for microplastics quantification and characterization. Suspected microplastic contamination in the procedural blanks, collected by 12 participating laboratories, had between 7 and 511 particles, with a mean of 80 particles per sample (±SD 134). The most common color and morphology reported were black fibers, and the most common size fraction reported was 20–212 μm. The lack of even smaller particles is likely due to limits of detection versus lack of contamination, as very few labs reported particles <20 μm. Participating labs used a range of QA/QC techniques, including air filtration, filtered water, and working in contained/‘enclosed’ environments. Our analyses showed that these procedures did not significantly affect blank contamination. To inform blank subtraction, several subtraction methods were tested. No clear pattern based on total recovery was observed. Despite our results, we recommend commonly accepted procedures such as thorough training and cleaning procedures, air filtration, filtered water (e.g., MilliQ, deionized or reverse osmosis), non-synthetic clothing policies and ‘enclosed’ air flow systems (e.g., clean cabinet). We also recommend blank subtracting by a combination of particle characteristics (color, morphology and size fraction), as it likely provides final microplastic particle characteristics that are most representative of the sample. Further work should be done to assess other QA/QC parameters, such as the use of other types of blanks (e.g., field blanks, matrix blanks) and limits of detection and quantification.