## 4 Conclusions  
The results of this study show that 98% of the samples were contaminated with MNPLs. The results of polymer composition with FTIR for the range of big particle size and with SEC-(APPI)-HRMS for the smallest ones were consistent. SEC-(APPI)-HRMS showed that the most frequently detected polymers in GITs of fish were PE, PP, PS and polysiloxanes, in agreement with other works. PE was detected in 84% of the samples and was also found at higher concentrations ranging from 0.55 to 3545.54 \(\mu\)g/g. The presence of plasticisers such as phthalates and adjiates should be highlighted among plastic additives. Among stabilisers, N, N-Bis(2-hydroxyethyl) dodecanamide and 2,5-di-tert-Butylhydroquinonewere some of the most frequently found. The results of this study highlight the complexity of plastic contamination and the necessity for integrative approaches to assess more realistically the potential impact of MNPL pollution in aquatic ecosystems and through the food web on human health. This study showed that suspected screening approaches are effective procedures to obtain a comprehensive vision of plastic contamination in complex matrices and inform about the potential transfer of this type of contamination to the food chain. Moreover, it provides information about the most recalcitrant groups of plastic contaminants and, therefore, those that should be closely studied. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/molecules28010239/s1](https://www.mdpi.com/article/10.3390/molecules28010239/s1)]([https://www.mdpi.com/article/10.3390/molecules28010239/s1](https://www.mdpi.com/article/10.3390/molecules28010239/s1)), Table S1--Visual observations and particle recount; Table S2--Compounds' parameters used for the prioritization; Table S3--List of samples and sampling details; Figure S1--Example of FTIR spectra of a fiber of the GIT filters; Figure S2--Examples of chromatograms, mass spectra and KMD plots of identified polymers. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Detection Frequency** & **Biodegradability * & **Log BAF * & **LD50 (mg/Kg)** & **Score** \\ \hline \textless{}5\% & Days & \textless{}2 & \textgreater{}1000 & 0 \\ \textless{}30\% & Weeks & 2–3 & 100–1000 & 25 \\ \textless{}50\% & Weeks–Months & 3–4 & 10–100 & 50 \\ \textless{}580\% & Months & 4–5 & 1–10 & 75 \\ \textgreater{}80\% & Recalcitrant & \textgreater{}5 & \textless{}1 & 100 \\ \hline \hline \end{tabular}
* * Estimations using EPI Suite software (United States Environmental Protection Agency, US EPA).  
\end{table} 
Table 3: Scoring system for prioritisation of the tentatively identified substances. **Author Contributions:** M.G.-T. Formal analysis, investigation, visualization and writing the original draft preparation; E.A. contribution to review and editing; D.A. Sampling and contribution to review and editing; M.L. Formal analysis, supervision, writing and edition; M.F. Conceptualization and resources, supervision, data curation and final draft revision and editing. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was supported by the IMAGE PROJECT (PID2020-116789 RB) from the Spanish Ministry of Science and Innovation. IDAEA-CSIC is Severo Ochoa Centre of Research Excellence (Spanish Ministry of Science and Innovation; Project CEX2018-000794-S). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable. **Acknowledgments:** [PERSON] acknowledges her grant PRE2021-099409. **Conflicts of Interest:** The authors declare no conflict of interest. * [PERSON] et al. (2002) [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON] Additives, plasticizers, small microplastics (<100 \(\upmu\)m), and other microlutter components in the gastrointestinal tract of commercial teleost fish: Method of extraction, purification, quantification, and characterization using Micro-FTIR. _Mar. Pollut.