Development and Demonstration of a Superior Method for Microplastics Analysis: Improved Size Detection Limits, Greater Density Limits, and More Informative Reporting

Since the emergence of mass-produced plastics in the 1940s, the global appetite for these materials has been increasing at a rapid rate. Estimates of cumulative plastic waste generated are as much as 6.3 billion metric tons. Only 9% of this material has been estimated to be recycled, while 79% of this material is deposited in landfills and the natural environment. As a result of this, microplastics are now ubiquitous in the environment. Their presence has been detected in surface waters, groundwater sources such as Karst waters, sediments, wildlife, and even consumer products. The major drawback with current efforts in microplastic sample preparation and counting is due to the difference in methods used by researchers. The National Oceanic and Atmospheric Administration (NOAA) was the first to publish a standard method to measure these materials. However, these methods were developed to address large plastic debris in surface water and beach samples. Furthermore, this method can only isolate and account for materials with a density less than 1.2 g/cm3. Many materials of interest, such as polyvinyl chloride, polyesters, and fluoropolymers, have a density greater than 1.3 g/cm3 and would therefore be unaccounted for in preparation by this method. To address the limitations in the current method, a new method has been developed that achieves a lower size detection limit (20 um x 20 um) and greater microplastic density limit (1.8 g/L). In addition, a novel reporting method using detailed size measurements of the microplastic present was implemented. This new approach for data reporting allows one to estimate the mass of microplastics present. Following development, the method was demonstrated with surface waters collected from three locations and fish larvae samples archived by the Illinois Natural History Survey.