Exploring the Effects of Sample Preparation on Microplastics: Assessing Chemical and Physical Changes and Recovery Rates
Author
Culina, Matea
Term
4. Term
Publication year
2023
Submitted on
2023-06-01
Pages
67
Abstract
Dette speciale undersøger, hvordan almindelige trin i prøveforberedelse kan påvirke mikroplastpartiklernes fysiske form, kemiske signatur og genfindingsgrad. Fem udbredte polymerer (HDPE, PET, PP, PS og PVC) blev testet i to størrelsesintervaller (0,5–3 mm og 3–200 µm) gennem en sekventiel protokol, der typisk anvendes til oprensning af miljøprøver: vaskemiddel (SDS), enzymbehandling (protease samt cellulose og viscozyme), Fenton‑oxidation og densitetsseparation i tungsaltopløsning. Store partikler blev fulgt med stereomikroskop og ATR‑FTIR for at vurdere ændringer i projekteret areal og i kemiske spektre, bl.a. ved hjælp af Pearson‑korrelationskoefficienter. Små partikler blev deponeret på siliconemembraner og analyseret med µFT‑IR‑billeddannelse og Raman‑mikroskopi; partikelidentifikation og kvantificering blev udført med spektralbiblioteker og siMPle‑software, og genfindingsgrader og størrelsesfordelinger blev beregnet for hvert trin. Arbejdet dokumenterer, at forbehandling kan ændre både udseende og spektra: enkelte PET‑ og PP‑partikler viste ekstra spektrale toppe og ændret intensitet efter SDS, og rester fra kemikalier kunne danne en “kage” ved filtrering, som besværliggjorde målinger. En sammenligning mellem µFT‑IR og Raman viste forskelle i detekterede partikler, matchindeks og lejlighedsvise fejlmatch i Raman‑biblioteket. Samlet peger resultaterne på, at valg af forbehandlingsprotokol og analyseteknik kan påvirke, hvor mange og hvilke mikroplastpartikler der identificeres, samt hvordan deres egenskaber tolkes, og specialet giver et grundlag for at afveje oprensning mod bevaring af partikelintegritet i mikroplaststudier.
This thesis investigates how common sample preparation steps can alter microplastic particles’ physical appearance, chemical signatures, and recovery. Five widely used polymers (HDPE, PET, PP, PS, and PVC) were tested in two size ranges (0.5–3 mm and 3–200 µm) using a sequential protocol typical for environmental clean‑up: a surfactant (SDS), enzymatic treatments (protease and a cellulose + viscozyme step), Fenton oxidation, and density separation in heavy salt solutions. Large particles were monitored by stereomicroscopy and ATR‑FTIR to track changes in projected area and spectra, including similarity assessed with Pearson correlation coefficients. Small particles were deposited on silicone membranes and analyzed by µFT‑IR imaging and Raman microscopy; particle identification and quantification used spectral libraries and the siMPle software, and recovery rates and size distributions were calculated for each step. The work documents that pre‑treatment can affect both morphology and spectra: some PET and PP particles exhibited additional spectral peaks and intensity changes after SDS, and chemical residues could form a “cake” on filters that hindered measurements. A comparison of µFT‑IR and Raman showed differences in detected particle counts, matching indices, and occasional misidentifications in the Raman library. Overall, the results indicate that the choice of preparation protocol and analytical technique can influence how many and which microplastic particles are identified and how their properties are interpreted, providing an evidence base for balancing sample clean‑up against preserving particle integrity in microplastic studies.
[This summary has been generated with the help of AI directly from the project (PDF)]
Keywords
Documents