Identifying a quick and efficient method of removing organic matter without damaging microplastic samples

Natural organic matter may confound the detection of microplastics, requiring a removal step. However, most available protocols arc long and lack information on removal efficiency and polymer degradation. Thus, we have determined the digestion efficiency (%) for a pool of organic matter (algae, driftwood, feathers, fish muscle, paraffin, palm oil) for five digestion solutions, hydrogen peroxide (H2O2), hydrogen peroxide with iron catalyst (H2O2 + Fe), potassium hydroxide (KOH), nitric acid (HNO3), and sodium dodecyl sulphate (SDS), under two temperatures (room temperature at 25 degrees C, 50 degrees C) and two periods ( 1,6 h). H2O2 + Fe and KOH at 50 degrees C for 1 h had the highest digestion efficiencies, of 65.9% and 583% respectively (mostly limited by driftwood and paraffin). Further testing revealed that H2O2 + Fe is more appropriate for plant material and KOH for animal tissue. Weight loss (%), Fourier transform infrared spectrometry and carbonyl index of 9 virgin and 6 weathered polymers (polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, cellulose acetate, nylon) revealed that only identification of cellulose acetate was hindered. Filters were also tested revealing that quartz and glass fibre filters are resistant to these protocols. Thus, a digestion protocol based on H2O2 + Fe or KOH at 50 degrees C for 1 h may be used on microplastic samples. (C) 2019 Elsevier B.V. All rights reserved.