Abstract
In the field of microplastics' quantification, efficient and reproducible methodology is still needed. Procedures of sample fractionation and transfer are often insufficiently reported, although fractionating a sample in similarly sized particles is a crucial prerequisite for the subsequent detection and identification process. At the same time, fractionation is error-prone as particles can be lost during transfer between different vessels. This article presents a four-step technique of sample preparation and microscopic examination, suited for different kind of environmental samples (e.g., water, sediment, soil): The sample is size-fractionated in a sieve cascade (I), rinsed from the sieve and vacuum-filtrated onto a filter (II), rinsed from the filter into a glass petri dish with a low amount of water (III), and examined under the microscope in wet or dry condition (IV). The technique manages on standard laboratory equipment and is reliable for fragments > 300 µm: In a validation experiment with polypropylene, the average recovery was 94 ± 13.5% (arithmetic mean ± standard deviation) and 100% (median), respectively.•Reliable sample transfer after wet-sieving.•Concentration of the pretreated sample in a very small amount of water.•Usage of transmitted light in microscopy.