Hajar Khaliliyan

We present an approach to overcome the challenges associated with the increasing demand of high‐throughput characterization of technical lignins, a key resource in emerging bioeconomies. Our approach offers a resort from the lack of direct, simple, and low‐cost analytical techniques for lignin characterization by employing multivariate calibration models based on infrared (IR) spectroscopy to predict structural properties of lignins (i. e., functionality, molar mass). By leveraging a comprehensive database of over 500 well‐characterized technical lignin samples – a factor of 10 larger than previously used sets – our chemometric models achieved high levels of quality and statistical confidence for the determination of different functional group contents (RMSEPs of 4–16 %). However, the statistical moments of the molar mass distribution are still best determined by size‐exclusion chromatography. Analyses of over 500 technical lignins offered also a great opportunity to provide information on the general variability in kraft lignins and lignosulfonates (from different origins). Overall, the effected savings in analysis time (>7 h), resources, and required sample mass combined with non‐destructiveness of the measurement satisfy key demands for efficient high‐throughput lignin analyses. Finally, we discuss the advantages, disadvantages, and limitations of our approach, along with critical insights into the associated chemical‐analytical and spectroscopic challenges.

Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high working temperatures in transformers constantly degrade paper insulators throughout their service life of up to 40 years. We approached the structural changes in oil-immersed cellulosic paper samples upon thermal stress in a study that compared unbleached softwood Kraft paper used as insulator paper with pure cotton cellulose paper. The model experiments used a thermal treatment in transformer oil at 170 °C for up to 14 days. The samples were characterized by means of¹³C CP/MAS NMR spectroscopy, mainly based on deconvolution of the C4 resonance. An automated, fast, and reproducible C4 resonance deconvolution employing the “Peak Analyzer” tool of OriginPro 2020 (OriginLab Corporation, USA) was developed and used to exploit¹³C CP/MAS NMR spectroscopy for the characterization of thermally stressed paper samples. Our results show that thermally induced structural changes depend heavily on the composition of paper, that hornification and coalescence of fibrils take place, and that the allomorph composition of cellulose crystallites is altered under the given conditions.Graphical abstract

This study is based on a two-stage approach. First, an experimental design was used in the optimization for the photodegradation of Rhodamine B dye (RhB) with Ag-, S-, N-doped TiO₂, with the concentration of RhB, pH and reaction time as optimization parameters. Second, the degradation rates were estimated through a kinetic study of RhB at the optimal conditions. The kinetic analysis was performed through the measurement of fluorescence excitation–emission matrices (EEMs) coupled with chemometrics. The number of the chemical components involved in the photodegradation process and their concentration and spectra profiles was established by multivariate curve resolution (MCR-ALS) and parallel factor (PARAFAC) analysis.