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Time-gated Raman spectroscopy and SERS as advanced technologies in bioprocess monitoring

  • Raman spectroscopy is becoming a powerful process analytical technology (PAT) tool. Until now Raman technology has not shown its full potential in bioprocess on-line monitoring due to several technical challenges. Because of only small? interference from water molecules, Raman-spectroscopy is in contrast to IR spectroscopy able to follow changes of metabolite concentrations in dilute aqueous solutions. Results from common CCD-based process Raman-spectrometers reveal only barely identifiable peaks with a dominating (fluorescence) background. To solve this, Raman spectroscopy needs: (A) an enhancement to increase the limit of detection (LOD), and (B) a reliable method to distinguish the Raman signal from the sample-related auto-fluorescence. SERS (surface enhanced Raman spectroscopy) acts as an optical "nano-antenna"-effect. It causes a dipolar localized surface Plasmon resonance effect due to noble metallic nanoparticles or roughened metal and improves the limit of detection (LOD)Raman spectroscopy is becoming a powerful process analytical technology (PAT) tool. Until now Raman technology has not shown its full potential in bioprocess on-line monitoring due to several technical challenges. Because of only small? interference from water molecules, Raman-spectroscopy is in contrast to IR spectroscopy able to follow changes of metabolite concentrations in dilute aqueous solutions. Results from common CCD-based process Raman-spectrometers reveal only barely identifiable peaks with a dominating (fluorescence) background. To solve this, Raman spectroscopy needs: (A) an enhancement to increase the limit of detection (LOD), and (B) a reliable method to distinguish the Raman signal from the sample-related auto-fluorescence. SERS (surface enhanced Raman spectroscopy) acts as an optical "nano-antenna"-effect. It causes a dipolar localized surface Plasmon resonance effect due to noble metallic nanoparticles or roughened metal and improves the limit of detection (LOD) significantly. Another new process-monitoring technique, which removes the fluorescence background in Raman-measurements is called time-gated Raman spectroscopy. It uses a picosecond pulsed Nd:YVO4-laser as emission source (exc= 532 nm) and a gated SPAD-array (Single Photon Avalanche Detector) detector instead of commonly used CCD (Charged Coupled Device)-detectors and CW (Continues Wave) laser emission. Time-Gate can measure the Raman-signal before the stronger fluorescence signal reaches the detector. In this study we utilized both SERS (Surface Enhanced Raman Spectroscopy) and time-gated Raman spectroscopy (TG-Raman) in combination on cell-free supernatant samples of an Escherichia coli cultivation with mineral salt media and a lactic acid bacteria fermentation with complex media. As a reference method for the estimation of amino acids and other metabolites, HPLC-RID and HPLC-FLD were used to evaluate the Raman-based detection. The quantitative evaluation of Raman data was performed by multivariate data analysis such as principal component analysis (PCA) and partial least squares regression (PLSR). For the first time, we can show that both qualitative and quantitative measurements are conducted successfully with both, SERS and time-gated Raman methods in industrially relevant media, so that a fast and reliable in situ or bypassed concentration measurement becomes feasible.zeige mehrzeige weniger

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Autor*innen:M. Koegler
Koautor*innen:Andrea PaulORCiD, K. Pellicer-Alborch, E. Anane, M. Birkholz, A. Bunker, T. Viitala, S. Junne, P. Neubauer
Dokumenttyp:Posterpräsentation
Veröffentlichungsform:Graue Literatur
Sprache:Englisch
Jahr der Erstveröffentlichung:2017
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:Chemometrics; PAT; Time-gate Raman
Veranstaltung:2. Photonics Finland, Optics and Photonics Days 2017
Veranstaltungsort:Oulu, Finland
Beginndatum der Veranstaltung:29.05.2017
Enddatum der Veranstaltung:31.05.2017
URL:http://www.photonics.fi/event/opd17-optics-photonics-days-2017/
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:01.08.2017
Referierte Publikation:Nein
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