Science Inventory

Assessment of filter subsampling and extrapolation for quantifying microplastics in environmental samples using Raman spectroscopy

Citation:

El Khatib, D., Troy D. Langknecht, Michaela A. Cashman, M. Reiss, K. Somers, H. Allen, Kay T. Ho, AND Robert M. Burgess. Assessment of filter subsampling and extrapolation for quantifying microplastics in environmental samples using Raman spectroscopy. MARINE POLLUTION BULLETIN. Elsevier Science Ltd, New York, NY, 192(July 2023):115073, (2023). https://doi.org/10.1016/j.marpolbul.2023.115073

Impact/Purpose:

Over the last decade, several studies have identified the presence of microplastics (MPs) in marine systems. However, there are many ways to measure MPs in the marine environment making it difficult to compare studies. In this study, we investigated one way of measuring MPs called Raman spectroscopy. Our goal was to simplify the use of Raman spectroscopy for measuring MPs. The findings of this study provide a reliable approach for more effectively performing Raman spectroscopy on MPs from marine systems.

Description:

A common method for characterizing microplastics (MPs) involves capturing the plastic particles on a filter after extraction and isolation from the sediment particles. Microplastics captured on the filter are then scanned with Raman spectroscopy for polymer identification and quantification. However, scanning the whole filter manually using Raman analysis is a labor-intensive and time-consuming process. This study investigates a subsampling method for Raman spectroscopic analysis of microplastics (operationally defined here as 45–1000 μm in size) present in sediments and isolated onto laboratory filters. The method was evaluated using spiked MPs in deionized water and two environmentally contaminated sediments. Based on statistical analyses, we found quantification of a sub-fraction of 12.5 % of the filter in a wedge form was optimal, efficient, and accurate for estimating the entire filter count. The extrapolation method was then used to assess microplastic contamination in sediments from different marine regions of the United States.