Fast Forward: Optimized Sample Preparation and Fluorescent Staining for Microplastic Detection

Abstract

The fast, affordable, and standardized detection of microplastics (MP) remains one of the biggest challenges in MP research. Comparable data are essential for appropriate risk assessments and the implementation of laws and limit values. The fluorescent staining of MP in environmental samples is a possible solution to this problem. This study investigates the optimization of a sample preparation process (hydrogen peroxide digestion) and the staining process (temperature, concentration, time, surfactants as staining aids) for using a specifically developed fluorescent dye for MP detection. The optimization is performed by comparing the sample preparation process and staining of MP from different polymers and natural particles. Further, the suitability of the optimized process for the detection of fluoropolymers and tire abrasion was tested. The results show that the optimized method (increased temperature and optimized stain concentration) can detect microplastics reliably with a total sample preparation and measurement time of 2.5–3 h per sample, reaching recovery rates of 93.3% (polypropylene) to 101.7% (polyester). Moreover, two of the three tested fluoropolymers could be detected reliably. Tire abrasion could not be detected with the here presented method, as the black color leads to strong quenching. A long-term study measuring the MP pollution in the effluent of a municipal wastewater treatment plant compared the optimized and original processes and confirmed the stability of the improved method for routine measurements and contamination control.

Presence of Microplastics in the Vaquita Marina Protection Zone in Baja California, Mexico

“…The samples were dried at 60 • C for 24 h; then they were subjected to oxidation with 30% H 2 O 2 (J.T.Baker ® , Phillipsburg, NJ, USA) for 3 h to eliminate the organic matter present. The resulting solution was vacuum filtered with Millipore equipment (Millipore Corporation, Burlington, MA, USA), using cellulose membranes with a diameter of 47 mm and a pore size of 8 µm [16,17]. The present MP were extracted manually with the help of dissecting forceps; the particles were rinsed with deionized water, dried with absorbent paper, and placed in glass Petri dishes.…”