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Development of advanced analytical tools for robust chemical characterization of lignin raw materials
Thesis (PhD)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613798915899392 |
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| access_status_str | Open Access |
| author | Mondlane, Chelsea Danielle |
| author2 | Lederer, Albena |
| author_browse | Lederer, Albena Mondlane, Chelsea Danielle |
| author_facet | Lederer, Albena Mondlane, Chelsea Danielle |
| author_sort | Mondlane, Chelsea Danielle |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134712 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:41:52.972Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134712 Development of advanced analytical tools for robust chemical characterization of lignin raw materials Mondlane, Chelsea Danielle Lederer, Albena Pfukwa, Helen Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Lignin -- Analysis Biomass chemicals Nuclear magnetic resonance Raw materials Thesis (PhD)--Stellenbosch University, 2025. Mondlane, C. D. 2025. Development of advanced analytical tools for robust chemical characterization of lignin raw materials. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/2c1533f6-9458-4f5f-9c6b-13cf88c7d57f ENGLISH ABSTRACT: Accurate molar mass determination of lignin is crucial for understanding its structure and tailoring its industrial applications. This thesis presents a comprehensive study employing various analytical techniques to assess the structure and molar mass of lignin extracted from lignocellulosic biomass through different isolation methods. The structural differences between lignin samples were elucidated using nuclear magnetic resonance (NMR) spectroscopy and fourier transform infrared (FTIR) spectroscopy, highlighting the impact of extraction protocols on lignin structure. Following the establishment of the structural motifs, the molar mass of lignin samples was evaluated. Several conventional and alternative approaches for molar mass measurements were investigated to overcome analytical challenges, including fluorescence interference, molecular aggregation, and limited solubility. Size exclusion chromatography (SEC) in combination with refractive index (RI), multiangle laser light scattering (MALS), fluorescence and viscometric detectors were used to comprehensively characterize different lignin samples. The combination of these detectors allowed in depth analysis of lignin, regarding their radius, molar mass, dispersity and conformation. Enhanced solubility and reduced aggregation were achieved through solvent optimization, yet persistent fluorescence led to overestimated molar mass values when using light scattering detection. To overcome the challenge of fluorescence, quenchers and iodine were added, leading to lower fluorescence intensity and a small decrease in molar mass. Implementing Universal calibration using a viscometric detector, circumvented fluorescence-related artifacts, yielding more reliable molar mass data. To further refine calibration methodologies and reduce dependency on using traditional calibration standards, a lignin sample was fractionated by employing two preparative fractionation methods. Absolute molar mass determination of lignin fractions was performed using matrix-assisted laser desorption ionization – time-of-flight (MALDI-ToF) mass spectrometry (MS), which indicated that high molar mass fractions were underestimated due to mass discrimination, thereby slanting the detected values toward lower molar masses. Therefore, the fractions appeared to be broadly distributed and displayed different fluorescence intensities. This study demonstrated the complexity of accurate lignin molar mass determination and offers a critical evaluation of the strengths and limitations of current analytical methods, thereby guiding the development of refined protocols and enabling more comprehensive structural analysis. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2026-01-05T07:38:46Z 2026-01-05T07:38:46Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134712 Stellenbosch University xxv, 174 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lignin -- Analysis Biomass chemicals Nuclear magnetic resonance Raw materials Mondlane, Chelsea Danielle Development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| title | Development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| title_full | Development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| title_fullStr | Development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| title_full_unstemmed | Development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| title_short | Development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| title_sort | development of advanced analytical tools for robust chemical characterization of lignin raw materials |
| topic | Lignin -- Analysis Biomass chemicals Nuclear magnetic resonance Raw materials |
| url | https://scholar.sun.ac.za/handle/10019.1/134712 |
| work_keys_str_mv | AT mondlanechelseadanielle developmentofadvancedanalyticaltoolsforrobustchemicalcharacterizationofligninrawmaterials |