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Combination of a cost-effective glass density separator followed by quantitative 1H-Nuclear Magnetic Resonance spectroscopy for the determination of microplastics in marine sediments
Summary
Scientists developed a cheap, simple way to measure tiny plastic particles (microplastics) hiding in ocean sediment, using basic lab equipment instead of expensive machinery. Testing beach sediments in Spain, they found real amounts of common plastics like PET (used in bottles) and LDPE (used in bags) in the seafloor. This matters because it gives researchers an affordable tool to track how much plastic pollution is building up in our oceans—plastic that can enter the food chain and eventually end up on our plates through seafood.
This work presents a method for determining the presence of microplastics in marine sediments. The method comprises a portable and cost-effective setup for separating microplastics using the principle of density floatation, followed by solubilization and quantitative qNMR spectroscopy. This method has been tested with polyethylene terephthalate (PET), polyvinyl chloride (PVC) and low-density polyethylene (LDPE) microplastics. The separation was carried out by using a novel home-made three-part glass setup and a separating solution of zinc chloride with a density of 1.6 g/cm 3 . Following Fenton clean-up, the supernatants were solubilized in suitable deuterated solvents and quantified by qNMR spectroscopy. The methodology was validated by the analysis of artificially spiked sediments at two levels, achieving recoveries between 71% and 105%, with relative standard deviation (RSD) below 22%. Method limits of quantification (MQLs) range from 15 to 245 ng/g. As a proof-of-principle application, sediment samples from three locations along the Galician coast (Northwest Spain) were analysed using the developed methodology. The concentrations of MP found in the marine sediments ranged from 62 to 186 ng/g of PET and from 192 to 229 ng/g of LDPE, with RSD ≤26%, whereas PVC was below the MQLs. This method allows for the estimation of the three polymer distribution and abundance in marine sediments in a swift, accurate and inexpensive way.