Efficient and sustainable microplastics analysis for environmental samples using flotation for sample pre-treatment

Microplastics analysis in solid environmental samples like sediments and soils requires complex preparation steps to eliminate interfering matrix components. This is often combined with the use of highly concentrated, expensive, and environmentally harmful chemicals. These sample preparation methods can be very time-consuming. Hence, with regard to green analytical chemistry, reduction of emissions and hazards, these sample preparation methods should be modified or avoided, and more environmentally friendly methods should be developed. The characterization and evaluation of the optimized hydrophobicity-water/air-based enrichment cell for microplastics (µSEP) are presented in this study. The separation mechanism of µSEP is based on the hydrophobic adhesion of microplastic on finely dispersed upstreaming air bubbles, serving as a sustainable and practical microplastic sample preparation method. The separation mechanism requires only water and air to considerably reduce the matrix for microplastic analysis. Using soil samples as an example, the applicability of the µSEP sample preparation method for the analysis of microplastics by Raman microspectroscopy (µRaman) and thermal extraction-desorption gas chromatography-mass spectrometry (TED-GC–MS) is demonstrated. Within a sample preparation time of 60 min, for polyethylene terephthalate (PET), an average recovery of 77% ± 11%, for polystyrene (PS), 42% ± 11%, and for polypropylene (PP) 65% ± 12% was determined. Furthermore, this study evaluates µSEP and other sample preparation methods regarding their ecotoxicological impact based on the recently released software tool AGREEprep. This tool considers ten individual criteria to cover influencing factors of green analytical chemistry.