On 9 June at 15.15 Shrikant Shivaji Pawade will defend his doctoral thesis “Metrological aspects of sampling and water/moisture determination on the example of lignin”.
Supervisors:
Prof. Ivo Leito, PhD, University of Tartu
Associate Prof. Koit Herodes, PhD, University of Tartu
Dr. Lauri Toom, PhD, University of Tartu
Oponendid:
Dr. Stephanie Bell, PhD, National Physical Laboratory (NPL), UK
Prof. Riina Aav, PhD, Tallinn University of Technology (TalTech), Estonia
Summary:
This doctoral thesis is dedicated to improving the reliability of quantitative lignin analysis, focusing on qNMR-based compositional characterisation and on the determination of water and moisture content. During this work, methods based on ATR-FTIR-PLS-R calibration models were developed, enabling rapid analysis of water and moisture content. The first part of the thesis addresses the accuracy of qNMR methods in lignin characterisation. A critical analysis of published studies showed that there are significant inconsistencies in the reporting of accuracy, and the measurand is often not clearly defined. Measurement uncertainty is rarely assessed comprehensively, and variability arising from sampling is often neglected. To address this, sampling-related uncertainty in lignin analysis was evaluated. The results showed that variability between subsamples constitutes a significant part of the total uncertainty in qNMR measurements and should always be taken into account. The second part of the thesis focuses on the determination of water and moisture content in lignin. Calibration samples were prepared from lignins of different origins. Water content was determined using vapour-phase coulometric Karl Fischer titration, supported by modelling of temperature-dependent water release to identify suitable evaporation temperatures. Moisture content was determined gravimetrically using oven drying and lyophilisation. Based on these results, a rapid and non-destructive ATR-FTIR-PLS-R method was developed for determining both water and moisture content. The method requires a small sample amount and minimal sample preparation. In conclusion, the thesis emphasises that reliable quantitative analysis requires a clear definition of the measurand and consideration of sampling-related uncertainty. A simple and rapid non-destructive ATR-FTIR-PLS-R method was developed for determining water and moisture content in lignin.
