Microplastic contamination of the marine environment has been reported globally. Its pervasiveness has highlighted the importance of accurate quantification to enable comparability within and between different environmental matrices. The potential efficacy of different methods to separate microplastics from their environmental sample matrix, however, is rarely validated. In this study, we examine the effects of four commonly used separation methods for seawater samples, namely, visual separation, density flotation, acidic digestion, and enzymatic digestion, using high-density polyethylene as our model microplastic. For each separation method, clarification efficiencies of the sample matrix, spiked recovery of high-density polyethylene microparticles, and potential changes in the chemical and physical characteristics of high-density polyethylene were assessed. High, albeit variable, recovery rates (>83%) of high-density polyethylene microparticles were achieved across all methods. Concentrated nitric acid was most effective at eliminating biological material from seawater samples. No apparent physical (i.e., length or color) or chemical changes due to separation treatments were observed in recovered high-density polyethylene microparticles, with the one exception that enzymatic digestion obscured polymer identification of high-density polyethylene. Our findings highlight the need to determine and report on the accuracy of separation methods for different polymer types and specific environmental sample matrices to ensure accurate quantification of marine microplastic contamination.

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微型塑料分离技术对海水样品的功效：使用高密度聚乙烯测试准确性

全球已经报道了海洋环境的微塑性污染。它的普遍性凸显了准确量化的重要性，以实现不同环境矩阵之内和之间的可比性。然而，很少有人验证不同方法从环境样品基质中分离微塑料的潜在功效。在这项研究中，我们以高密度聚乙烯为模型微塑料，研究了四种常用分离方法对海水样品的影响，即目测分离，密度浮选，酸性消化和酶消化。对于每种分离方法，样品基质的净化效率，高密度聚乙烯微粒的加标回收率，评估了高密度聚乙烯的化学和物理特性的潜在变化。在所有方法中，都可以实现高密度聚乙烯颗粒的高回收率（> 83％）。浓硝酸在去除海水样品中的生物物质方面最有效。没有明显的身体（即，长度或颜色），或者由于分离处理化学变化中回收高密度聚乙烯微粒进行观察，与所述一个例外是酶消化模糊的高密度聚乙烯的聚合物鉴定。我们的发现强调需要确定和报告不同聚合物类型和特定环境样品基质的分离方法的准确性，以确保准确定量海洋微塑料污染。