From sieve to microscope: An efficient technique for sample transfer in the process of microplastics’ quantification

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.

Microplastics in Namibian river sediments – a first evaluation

“…In this study, the guidelines from Cowger et al [42] were followed (see supplementary data 1). The procedure of density separation was derived from Imhof et al [28], and further process steps were evolved in the laboratory for microplastics at the Faculty of Physics, University of Marburg [45]. The sampling was carried out with wood shovels and spoons that were wet cleaned before.…”

Investigating the dispersal of macro- and microplastics on agricultural fields 30 years after sewage sludge application

“…Material smaller than 300 µm was discarded. The sieve residues were then cleaned with filtered deionized water and transferred to cellulose filters (LLG-Labware GmbH) via vacuum filtration and stored in glass petri dishes 54 . To distinguish between remaining organics and potential microplastics, the filters were stained with a Nile Red solution (20 μg mL −1 Nile Red, Sigma-Aldrich GmbH, dissolved in an ethanol-acetone (1:1) mixture) and then dried (50°C, 10 min) 55 , 56 .…”

Meso- and microplastic distribution and spatial connections to metal contaminations in highly cultivated and urbanised floodplain soilscapes – a case study from the Nidda River (Germany)

“…Afterwards, the remaining sample material, consisting of organic material and potential plastic particles, was separated into the following size classes using stainless-steel sieves (Ø 75 mm, Atechnik, Leinburg, Germany), and filtered (> 50 μm) deionised water: > 1000 μm, > 500 μm and > 300 μm. After sieving, the sieve residues were filtered via vacuum-filtration on cellulose filters (Ø 47 mm, LLG-Labware, Meckenheim, Germany), and then transferred to glass petri dishes (Ø 90 mm or 200 mm) by rinsing with deionised water and drying at 50 °C for 2 days, according to Prume et al [48].…”