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A simple overflow density separation method that recovers >95% of dense microplastics from sediment
Summary
Scientists developed a simple, low-cost method for separating dense microplastics from sediment samples using a zinc chloride solution overflow technique. The method recovered over 95% of test microplastic particles, including hard-to-capture dense types like PVC and rubber. Better detection methods like this are important because accurately measuring microplastic contamination in the environment is the first step toward understanding human exposure risks.
Density separation can isolate microplastics from environmental samples containing sediment. Typically, a solution added to sediment causes microplastics with lower densities to float. The solution of choice can influence the recovery of different particles since denser solutions can separate a greater range of microplastics. The equipment and procedural complexity further influence density separation protocols and microplastic recoveries. Zinc chloride (ZnCl) is frequently used to isolate high-density polymers from environmental samples yet is rarely validated with simple, well-described protocols. A simple overflow method using ZnCl to isolate microplastics from sediment samples is described following a 3-step process: (1. Separation) ZnCl (1.7 g cm) solution is added to a sediment sample, agitated then settled; (2. Overflows) buoyant particles at the surface of the solution are overflowed twice; (3. Filtration) the overflowed solution is filtered. In a validation experiment with polyamide, rubber, polyvinyl chloride and polyethylene terephthalate/polyester, the mean recovery using this overflow method was 96 % ± 0.6 (standard error). This overflow density separation method proposes an accessible and reliable protocol to extract medium and high-density microplastics.•Microplastic separation with concentrated ZnCl solution•Simple overflow of buoyant particles•Reliable extraction of microplastics.