The rising evidence of microplastic pollution impacts on aquatic organisms in both marine and freshwater ecosystems highlights a pressing need for adequate and comparable detection methods. Available tissue digestion protocols are time-consuming (> 10 h) and/or require several procedural steps, during which materials can be lost and contaminants introduced. This novel approach comprises an accelerated digestion step using sodium hydroxide (NaOH) and nitric acid (HNO3) in combination to digest all organic material within one hour, plus an additional separation step using sodium iodide (NaI) which can be used to reduce mineral residues in samples where necessary. This method yielded a microplastic recovery rate of ≥ 95 % and all tested polymer types were recovered with only minor changes in weight, size and colour with the exception of polyamide. The method was also shown to be effective on field samples from two benthic freshwater fish species, revealing a microplastic burden comparable to that indicated in the literature. In consequence, the present method saves time, minimizes the loss of material and the risk of contamination and facilitates the identification of plastic particles and fibres, thus providing an efficient way to detect and quantify microplastics in the gastrointestinal tract of fishes.
Samuel Roch and Alexander Brinker, Environ. Sci. Technol., Just Accepted Manuscript, March 30 2017