Structure – Interdisciplinary topic “sample preparation”
Sample preparation begins with the transfer of samples (aqueous and solid) from the field to the laboratory. Here, work and health-related aspects in wastewater sample analysis are particularly important, especially with respect to the following analysis. Therefore, additional disinfection and sterilization steps may be necessary; however they must not impact the integrity of the sampled materials. Irradiation techniques (gamma/beta sterilization) or sterilization with ethylene oxide or plasma could be applied, extending/replacing typical steam sterilization at 121°C or higher temperatures up to 142°C which leads to melting of polyethylene particles.
Due to the low percentages of microplastic particles in comparison to other materials in aqueous and solid samples, a direct analysis of samples as they reach the laboratory is not foreseeable. Instead, the solid materials of samples must be enriched. Here, sizes of >1 µm are in the focus if the diameter and the number concentration of particles are to be determined. The methods for the determination of mass concentrations will mostly focus on particles >10 µm, since very small particles do barely contribute to mass concentration. However, small particles are likely to be particularly important with respect to biological effects.
Another substantial part of sample preparation is the separation of microplastic particles from all other organic and inorganic solids. Density separation techniques can be applied to enrich lighter and heavier microplastic particles. Interfering organic solids can likely be oxidized or treated enzymatically in order to separate them from the target particles. The applied sample preparation techniques will be compared by means of an exchange of sample materials.