Assessment of novel measurement technologies for process monitoring and use of chemometric advances to facilitate their application

Student thesis: Doctoral Thesis

Abstract

Mid-infrared (MIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy are common laboratory techniques, but are not so widely used in process analysis. The high attenuation of MIR light inhibits the ability to locate delicate instruments away from harsh processes using long lengths of optical fibre, and the large size and cost of high-field NMR spectrometers prevent them from being easily installed in process plants. Recent advances in technology have led to the availability of miniaturised, robust MIR spectrometers and benchtop NMR spectrometers operating at low field.The performance of a novel, robust MIR spectrometer, designed for use in process environments, was assessed for the quantitative in situ analysis of liquids and was found to be comparable to a laboratory MIR spectrometer. A reaction was then monitored using the novel spectrometer and accurate predictions of concentration could be obtained by multivariate curve resolution. This demonstrates the suitability of the spectrometer for in situ process monitoring. Calibration transfer between the two MIR spectrometers was also performed, demonstrating the ability to build a model in the laboratory for subsequent application to a process.The instrumental stability of a low-field NMR spectrometer was evaluated, and when multiple samples were analysed, shifting of peaks and deterioration of lineshape occurred over time. To eliminate peak shift, a range of alignment methods were assessed. Alignment was successful for small peak shifts, but less effective when large peak shifts were present. However accurate predictions of concentration could still be obtained by PLS.Calibration transfer and reference deconvolution were compared as a solution to lineshape deterioration, and the transfer of PLS models between low-field NMR spectra collected under different conditions was demonstrated. Calibration transfer was found to be more effective overall, and produced accurate predictions of concentration. These results demonstrate the suitability of low-field NMR spectroscopy for quantitative analysis.
Date of Award28 Feb 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council) & University of Strathclyde
SupervisorAlison Nordon (Supervisor) & David Littlejohn (Supervisor)

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