by Dan Teano, SHIP intern
Darius Sanford (Class of 2018) is a Marine Science major at Savannah State University located in Savannah, Georgia. After graduating next spring, Sanford plans to pursue a Master’s degree in Environmental Law or Environmental Policy. In his spare time, Darius reads and listens to current events worldwide and also writes science fiction novels.
Sanford is a summer intern with the Sandy Hook Internship Program (SHIP) at the Northeast Fisheries Science Center’s (NEFSC) Howard Laboratory in New Jersey. Under the mentorship of NEFSC chemist Ashok Deshpande, Sanford is studying how microplastics end up in marine and estuarine ecosystems, specifically fish stomachs. Microplastics can have serious environmental, economic and health implications, understanding the sources and fates of it is important for cultivating healthy and productive ecosystems. To begin, Sanford must first collect an array of plastics from everyday household items and clothing fabrics, like this yellow plastic mesh.
Next, Sanford needs to create a source library – a series of known plastics that when analyzed carries a uniquely identifiable chemical fingerprint. He uses an instrument called a Pyrolysis Gas Chromatography-Mass Spectrometry (Pyr-GC-MS) to create those chemical fingerprints. So far, Sanford has created 15 different chemical fingerprints for his source library.
Once the source library is created, Sanford can process fish stomachs for evidence of microscopic pieces of plastic, called microplastics, that he’ll analyze for its chemical fingerprints to compare against his library. Standing a few steps back, Sanford watches as the fish stomach is processed by an ultrasonic probe which sounds like the pulsing of an electric drill boring through metal. The sonicator emulsifies and disintegrates the fish stomach tissue cells into a slurry. When the slurry reaches a Slushee-like consistency, Sanford will pour the slurry over a membrane filter and drain off the liquid. Using a microscope, he then collects items off the filter that at first glance look like small bits of microplastic.
Darius then places each bit of microplastic in separate quartz tubes to be analyzed in the GC-MS. Here Sanford analyzes the microplastic sample by heating it to 650 degrees Celsius (1202 degrees Fahrenheit). At this temperature, the solid plastic polymer is pyrolyzed and transformed into a smaller gaseous fragment molecules, revealing its chemical fingerprint.
As the sample runs, Sanford can see in real time the chemical fingerprint of his sample. He shows a fellow intern, Rory Kelly, three characteristic chemical peaks. This he says is a classic signature for polyethylene, a commonly used plastic for wrapping and containing food. With the accumulation of microplastics in estuarine and marine ecosystems an ever increasing scientific and societal concern, Sanford’s intern project helps fill our knowledge gaps surrounding the identification of polymer type and perhaps the source of products that turn into microplastics in the environment.