Mathalon and Hill  used H202 (30%) at 55°C-65°C to digest mussel soft tissue, and although largely effective, the authors noted “flakes of debris” remained. Li et al.  also applied this method, but incubated samples in an oscillating incubator and then at room temperature for 24-48 h. Avio et al.  similarly tested alternate treatments in digesting intestinal tracts of mullet (Mugil cephalus). Avio et al.  identified that direct application of H202 resulted in only a 70% retrieval of spiked microplastics, with losses linked to H,0, foaming. A number of studies noted excessive foaming might obscure samples or lead to sample loss [72,78,92]. A density separation of stomach contents with hypersaline (NaCl) solution followed by digestion of isolated material with 15% H202 resulted in a much improved 95% recovery rate for spiked microplastics. Dehaut et al.  trialed 0.27 M K2S208 with 0.24 M NaOH in digesting biological tissues. This mixture was efficient in digesting biogenic material (<99.7% mass reduction), but the authors noted its expense and highlighted issues with crystallization of the digestive solutions and incomplete digestion causing blockages during filtration. Avio et al.  observed that 15% H,02 had no visible impact on PE or PS microspheres, although a slight modification to FTIR spectra was observed. Conversely, Nuelle et al.  identified some visual deformities to exposed plastic and quantified a 6.2% loss in size for PP and PE particles (<1 mm). K2S208 resulted in no changes in the mass or appearance in the majority of exposed polymers, but caused complete dissolution of cellulose acetate .
Naji et al.  applied the digestion method using 30% H202 to remove soft tissue of different mollusks. This was followed by filtration of the solution through 25 pm filter paper using a vacuum system.
Collard et al.  digested fish stomach contents, in an overnight exposure with ~3% NaClO. Filtered digestants were subsequently washed with 65% HN03 and digested in a 10:1 NaC10:HN03 solution for 5 minutes. The technique caused no visible degradation of a range of polymers (PET, PVC, PE, PP, PS, PC or PA).