SiMPore researchers presented two posters at the recent Society of Environmental Toxicology and Chemistry North America 43rd Annual Meeting. The work demonstrates a number of studies comparing SiMPore’s silicon nanomembrane filters against a panel of conventional polymer filters in terms of filtration and optical imaging performance with both model particles and real-world samples.
Development of a Novel 20 μm Cut-off Microporous Silicon Nitride Membrane for Separating and Analyzing Microplastic Particles in Potable Water
Horan et al, 2022, Society of Environmental Toxicology and Chemistry North America 43rd Annual Meeting.
Track-etched polycarbonate (PCTE) membranes have been used as a filtration standard for microplastic (MP) capture and analysis across a variety of studies.
However, the track-etch method creates pores of varying angles that complicate on- membrane particle analysis and sometimes create merged multi-pores that allow passage of MPs > 20 μm. Additionally, the membrane’s overall ~3 μm thickness makes it prone to folding and wrinkling, which may complicate microscopy analysis.
To address these issues, a novel 20 μm gold-coated microporous silicon nitride (MPSN-Au) membrane was developed and compared directly against gold-coated PCTE (PCTE-Au) membranes via manual manipulation and processing time, pore characteristics, light microscopy particle analysis, and Raman/FTIR analysis.
We found that on an area-normalized basis, MPSN-Au membranes offered greater gas and water flux over PCTE-Au. The regular pore geometry of MPSN-Au membranes made particle imaging and spectral analysis more consistent and easier to discriminate between captured PS particles, when compared to PCTE-Au membranes.
Total handling and processing time for each membrane was compared, which determined that the total processing time (including filtration, automated image acquisition, and particle counting) was 161.56% faster on average for MPSN-Au than PCTE-Au membranes.
In an 8-hour workday, 85.13% more MPSN-Au membranes can be handled, processed, and imaged than PCTE-Au, which equates to 66 vs 26 total samples, respectively.
Overall, these data demonstrate the utility of MPSN-Au membranes and suggest they can significantly improve testing time-related efficiency in all aspects of normal use-case situations as compared to PCTE-Au membranes.
Comparative Evaluation of Filtration and Imaging Properties of Filter Membranes for Microplastic Capture and Analysis
Carter et al, 2022, Society of Environmental Toxicology and Chemistry North America 43rd Annual Meeting.
Pollution by microplastics (MPs) in drinking, fresh, and ocean waters, as well as food and beverages, is a growing problem that is now well-recognized in both the popular media and scientific literature. Concerning levels of MPs have been found in food and local waters, as well as in human tissues. Several government regulatory bodies have, or are in the process of, implementing mandatory MP drinking water testing. Consequently, there are needs for greater understanding of the performance characteristics of common MP analytical methods and for standardizing methods and reporting.
Here, we report on the comparative evaluation of the filtration and imaging properties of five filter membranes capable of MP capture and analysis. This study was undertaken as part of an inter laboratory methods evaluation study coordinated by the Southern California Coastal Water Research Project. We compared track-etched polycarbonate +/- gold coating (PCTE and PCTG), polytetrafluoroethylene (PTFE) porous silicon (PS) and gold-coated microslit silicon nitride membranes (MSSN-Au). We further demonstrate use of MSSN filters to monitor MP entrainment along a municipal drinking water delivery network from the producing plant to a point of use drinking fountain at a local University.