Equipment: MRI: Track 1 Acquisition of a Raman Spectroscopy System to Enhance Microplastic Screening in Environmental and Biological Samples

Microplastics are widely recognized as contaminants of concern due to their ubiquity in the environment, widespread presence in aquatic and terrestrial food webs, and their potential to adversely impact environmental and human health. An award was made to the College of Charleston for the purpose of acquiring a Raman spectroscopy system to enhance the study of microplastics in environmental samples.

Raman spectroscopy is a technique to determine the composition of materials based on the interaction between monochromatic light from a laser and molecules in a sample. When paired with an optical microscope, micro-Raman spectroscopy can be applied to samples of at least 1μm in diameter, allowing for an accurate and efficient method to detect particles and determine the polymer composition of suspected microplastics in environmental samples.

This system will be shared among faculty at three universities including the College of Charleston (located in Charleston, SC), The Citadel (located in Charleston, SC), and the University of South Carolina (located in Columbia, SC). These universities have an extensive history of collaboration in addressing the environmental impacts of microplastics in aquatic and estuarine ecosystems.

The Raman spectroscopy system will be used for research and educational purposes, providing undergraduate and graduate students the opportunity to be trained on state-of-the art instrumentation that is widely recognized to be the “gold standard” in the field of environmental microplastic assessment.

Microplastic screening of environmental samples (e.g., biological tissue, sediments, gastrointestinal contents) involves a multi-step process including the manual identification of suspected plastic particles using stereo microscopy and hot needle testing, followed by physio-chemical characterization. Visual inspection of samples is time-consuming and labor intensive, given the thousands of organic and inorganic impurities that can be found in heterogeneous substrates, and manual inspection of environmental samples can also lead to false detections and particle misclassification.

Polymeric composition for particles > 500 μm can be determined using Fourier-transform infrared (FTIR) spectroscopy; however, most particles in environmental samples are smaller than the FTIR threshold, hindering the ability to confirm a plastic origin. These limitations can cause significant delays in reporting and publishing of research findings.

The Raman spectroscopy system acquired for this project will include a confocal microscope with a motorized stage, two lasers (532 and 785 nm), darkfield illumination, rapid imaging software, and a microplastic-specific spectra library. This system will allow researchers to determine the polymer composition of suspected microplastics <500 μm in diameter. Automated scanning will improve the accuracy of particle counts, and access to a microplastics-specific spectra library will provide precise particle composition results.

Also, the multiple objectives and light options (brightfield/darkfield) will enhance the detection of transparent films and fibers, which are abundant particles in all environmental samples. Since micro-Raman spectroscopy is considered the ‘gold standard’ for particle detection and characterization, the publication process will be expedited and reviewed favorably among high-impact journals.

Finally, micro-Raman spectroscopy is an interdisciplinary tool with applications across chemistry, physics, biology, and materials science fields, which will facilitate interdisciplinary collaboration within and among universities.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.