Strategies for Maximizing Microplastic Isolation and Collection on Membrane Flters During the Vacuum Workflow for Use in Chromatographic, Spectroscopic and Microscopic Methods

Analyzing Microplastics in the Environment
Oral Presentation

Prepared by L. Lozeau1, K. Sydlowski1, G. Shah1, R. Muralidharan2
1 - MilliporeSigma, 400 Summit Drive, Burlington, MA, 01803, United States
2 - Sigma-Aldrich, Inc., P.O Box 14508, St. Louis, MO, 63178, United States


Contact Information: [email protected]; 781-496-5656

ABSTRACT

The development of analytical methods to detect microplastics in the environment is an increasing priority due to mounting evidence of their negative impacts on human health. While current methods revolve around the use of chromatographic (e.g., pyrolysis-GC-MS) or spectroscopic (e.g., µFTIR, LDIR, or Raman microscopy) analysis techniques, sample preparation strategies for isolating microplastics are as heterogeneous as the particles themselves. Despite this, the majority workflows require a critical step that uses vacuum filtration hardware to concentrate microplastics on a membrane filter, followed by microscopic characterization (for example, using Nile Red fluorescence). As with any particle analysis workflow, a key concern with microplastics characterization is loss of particles during sample preparation. Previously, we observed particle loss during the vacuum filtration step due to the aggregation of particles at funnel-membrane interface and afterward due to handling challenges. Therefore, the purpose of this study was to determine which key features of vacuum filtration hardware played the most critical role(s) in the accurate collection of microplastics on filters, by comparing microplastic loss and recovery after filtration with hardware of different materials, shapes, and diameters on three different filter materials. Further, we examined strategies for optimally handling membranes after filtration to reduce particle loss, such as backing with stiff substrates. We found these strategies were applicable not only for environmental detection, but also for assessing the toxicity of microplastics. Finally, we implemented these strategies in three case studies: (1) the fluorescent detection of microplastics using Nile Red, (2) the detection of microplastics using pyr-GC-MS via ASTM D8401, and (3) in a cell-based assay in a filter plate to assess the toxicity of microplastics. Together, these studies provide valuable insights for choosing the optimal filtration devices for the accurate isolation, identification, handling, analysis and characterization of microplastics in environmental matrices.