62421 2025 eng 1 10 233 article Elsevier Ltd. Amsterdam 1 -- -- -- The use of low-field nuclear magnetic resonance (NMR) spectroscopy enables real-time reaction monitoring in contrast to time-consuming gas chromatography or off-line high-field NMR measurements. In this study, NMR spectroscopy is demonstrated as a novel process analytical technology (PAT) tool in the downstream processing of polyhydroxyalkanoate (PHA) biopolymers. On-line NMR spectroscopy measurements were performed using a Spinsolve 43 Carbon Ultra instrument in a fully automated mode with a flow-assembly based on PTFE tubing. Single-scan NMR spectra were acquired for real-time monitoring of the extraction process of the PHA copolymer poly(hydroxybutyrate-co-hydroxyhexanoate) with 13.5 mol.% hydroxyhexanoate [P(HB-co-13.5 mol.%HHx)] from Ralstonia eutropha biomass using chloroform or acetone as PHA solvents at lyophilized cell loadings of 20–120 g L􀀀 1. The reproducibility and reliability of low-field NMR spectroscopy was comparable to high-field NMR spectroscopy, with superior performance in terms of time. The correlation between the results of on-line monitoring using low-field NMR spectroscopy and off-line analysis using gas chromatography (GC) showed a correlation coefficient of >94 %. The versatility of low-field NMR spectroscopy for elucidating reaction kinetics, facilitating endpoint determination and accelerating extraction processes by maximizing solubility is highlighted as plateau values were reached within 6–10 min for chloroform and acetone, respectively. This novel low-field NMR spectroscopy application promotes a new monitoring approach for downstream PHA processing and supports process development and optimization. Polymer Degradation and Stability 10.1016/j.polymdegradstab.2025.111188 urn:nbn:de:kobv:b43-624215 1873-2321 publish 25.08.2025 Creative Commons - CC BY - Namensnennung 4.0 International Isabel Thiele Björn Weiske Sebastian L. Riedel Klas Meyer eng uncontrolled Polyhydroxyalkanoate eng uncontrolled Extraction eng uncontrolled NMR eng uncontrolled Ralstonia eutropha eng uncontrolled Downstream processing Analytische Chemie Chemische Verfahrenstechnik 1 Analytische Chemie; Referenzmaterialien 1.4 Non-Target-Analytik Chemie und Prozesstechnik Chemische Charakterisierung und Spurenanalytik Verlagsliteratur Datei für die Öffentlichkeit verfügbar ("Open Access") Wissenschaftliche Artikel der BAM Anlagensicherheit und Prozesssimulation Bundesanstalt für Materialforschung und -prüfung (BAM) https://opus4.kobv.de/opus4-bam/files/62421/1-s2.0-S0141813024009917-main.pdf