DASC-PM v1.0 : ein Vorgehensmodell für Data-Science-Projekte

Das Thema Data Science hat in den letzten Jahren in vielen Organisationen stark an Aufmerksamkeit gewonnen. Häufig herrscht jedoch weiterhin große Unklarheit darüber, wie diese Disziplin von anderen abzugrenzen ist, welche Besonderheiten der Ablauf eines Data-Science-Projekts besitzt und welche Kompetenzen vorhanden sein müssen, um ein solches Projekt durchzuführen. In der Hoffnung, einen kleinen Beitrag zur Beseitigung dieser Unklarheiten leisten zu können, haben wir von April 2019 bis Februar 2020 in einer offenen und virtuellen Arbeitsgruppe mit Vertretern aus Theorie und Praxis das vorliegende Dokument erarbeitet, in dem ein Vorgehensmodell für Data-Science-Projekte beschrieben wird – das Data Science Process Model (DASC-PM). Ziel war es dabei nicht, neue Herangehensweisen zu entwickeln, sondern viel-mehr, vorhandenes Wissen zusammenzutragen und in geeigneter Form zu strukturieren. Die Ausarbeitung ist als Zusammenführung der Erfahrung sämtlicher Teilnehmerinnen und Teilnehmer dieser Arbeitsgruppe zu verstehen

Analysis of lignin monomers and oligomers in technical lignins using chromatography and mass spectrometry

Lignin is the most abundant aromatic biopolymer on earth and has the potential to play an important role in the transition from an oil-based refinery to a biorefinery-based industry. The isolation of lignin from the biomass can be achieved by several different technical processes and isolated lignins are referred to as technical lignins in literature. During the last decades, the conversion of technical lignins into economically valuable aromatic chemicals became a growing research interest.For the understanding of the chemical nature of technical lignins and the understanding of the chemical reactions occurring during conversion processes, selective and sensitive analytical methods are crucial. Therefore, analytical methods using liquid chromatography (LC) and supercritical fluid chromatography (SFC) coupled to electrospray ionisation–mass spectrometry (ESI–MS) were developed in this thesis work. Main emphases were set on the optimisation of the ESI of lignin monomers (LMs), the identification of unknown LMs and lignin oligomers (LOs) in complex technical lignin samples and on the separation of LMs and LOs using SFC.Several ESI parameters were studied for the ionisation of LMs to identify which ESI parameters have significant influences. First, the ESI of a wide range of LMs were studied using SFC/ESI–MS, then the influence of specific ESI parameters on different groups of LMs was analysed. Significant ESI parameters, such as the concentration of the makeup solvent additive or the desolvation gas temperature, were identified as significant parameters for the ESI of a wide range of LMs. Furthermore, it has been shown that for the different groups of LMs, different ESI parameters are of importance. For instance, compounds with two methoxy groups seem to need more desolvation energy compared to compounds with one or no methoxy groups.The identification of unknown LMs and LOs in technical lignin samples using MS is very challenging due to the very complex sample mixtures and the lack of commercially available reference standards. Therefore, a non-targeted analysis strategy using SFC/ESI–high-resolution multiple stage tandem MS combined with Kendrick mass defect-based principal component analysis–quadratic discriminant analysis classification models was developed. The developed method assures an identification confidence of level 3 without the need of reference standards and without the study of MS fragmentation patterns. Furthermore, it was demonstrated that a higher identification confidence level and tentative chemical structures can be obtained with multiple stage tandem MS.For the characterisation of unknown compounds in complex samples, clean mass spectra of the investigated compound are useful. In this work, the application of SFC for the separation of LMs and LOs has been investigated using a stationary phase screening approach. It was found that a SFC stationary phase with both hydrogen bonding and π-π-interaction chemistries offers the highest overall resolution power combined with a selective separation of LMs and lignin dimers

Identification of lignin oligomers in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMSn)

Kraft lignin is the main source of technically produced lignin. For the development of valuable products based on Kraft lignin, its molecular structure is important. However, the chemical composition of Kraft lignin is still not well known. So far, the analysis of Kraft lignin by mass spectrometry (MS) has been mainly focused on monomeric compounds. Previous MS studies on lignin oligomers (LOs) considered only synthesised LO standards and/or lignins produced by processes other than the Kraft process. Furthermore, published MS methods suffer from using high resolution only in the MS1 stage in multiple-stage tandem MS methods. A high resolution in all MSn stages would provide more detailed information about LO fragmentation pathways. Since lignin samples are complex mixtures of a large number of similar phenolic compounds, the selection of tentative LOs in the MS data is challenging. In this study, we present a method for non-targeted analysis of LOs in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMSn). A pre-selection strategy for LOs has been established based on a data-dependent neutral loss MS3 method in combination with a principal component analysis-quadratic discriminant analysis classification model (PCA-QDA). The method was optimised using a design of experiments (DOE) approach. The developed approach improved the pre-selection of tentative LOs in complex mixtures. From 587 detected peaks, 36 peaks were identified as LOs

Separation of monomeric and dimeric phenolic compounds in lignosulphonate lignin on different stationary phases using ultrahigh-performance supercritical fluid chromatography

Lignin is a promising renewable resource and its valorization could help to reduce our dependency on fossil carbon resources. Especially the production of small molecular weight and economically valuable compounds, such as vanillin, are of interest. A good separation of the sample components is crucial for a confident identification of compounds in complex sample mixtures using for instance mass spectrometry. In this work, the resolving power and selectivity of five different stationary phases for ultrahigh-performance supercritical fluid chromatography were studied for the class separation of lignin monomers (LMs) and dimers (LDs). A separation of LMs and LDs will help to identify such compounds in complex technical lignin samples. It could be shown that stationary phases with both hydrogen-bonding acceptor and donator groups offer high overall resolving power, while π-π-interactions are advantageous for the separation of the two compound classes. An almost complete separation combined with an improved overall resolving power was achieved with the 1-aminoanthracene stationary phase, which offers both hydrogen-bonding interactions and π-π-interactions

Ultra-high-performance supercritical fluid chromatography with quadrupole-time-of-flight mass spectrometry (UHPSFC/QTOF-MS) for analysis of lignin-derived monomeric compounds in processed lignin samples

The conversion of lignin to potentially high-value low molecular weight compounds often results in complex mixtures of monomeric and oligomeric compounds. In this study, a method for the quantitative and qualitative analysis of 40 lignin-derived compounds using ultra-high-performance supercritical fluid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPSFC/QTOF-MS) has been developed. Seven different columns were explored for maximum selectivity. Makeup solvent composition and ion source settings were optimised using a D-optimal design of experiment (DoE). Differently processed lignin samples were analysed and used for the method validation. The new UHPSFC/QTOF-MS method showed good separation of the 40 compounds within only 6-min retention time, and out of these, 36 showed high ionisation efficiency in negative electrospray ionisation mode. [Figure not available: see fulltext.

Non-targeted analysis strategy for the identification of phenolic compounds in complex technical lignin samples

Lignin is the second most abundant biopolymer in nature and a promising renewable resource for aromatic chemicals. For the understanding of different lignin isolation and conversion processes, the identification of phenolic compounds is of importance. However, due to the vast number of possible chemical transformations, the prediction of produced phenolic structures is challenging, and a non-targeted analysis method is therefore needed. In this study, we present a non-targeted analysis method for the identification of phenolic compounds using ultra-high-performance supercritical fluid chromatography/high-resolution multiple stage tandem mass spectrometry combined with a Kendrick mass defect-based classification model. The method was applied to a Lignoboost Kraft lignin (LKL), a sodium Lignosulphonate lignin (SLS) and a depolymerised Kraft lignin (DKL) sample. In total, 260 tentative phenolic compounds were identified in the LKL sample, 50 in the SLS sample and 77 in the DKL sample

Identification of Phlorotannins in the Brown Algae, Saccharina latissima and Ascophyllum nodosum by Ultra-High-Performance Liquid Chromatography Coupled to High-Resolution Tandem Mass Spectrometry

Phlorotannins are bioactive polyphenols in brown macroalgae that make these algae interesting as healthy food. Specific phlorotannins are, however, seldom identified, and extracts from different species are often only analysed for total phenolic content (TPC). In this study, our focus was to identify phlorotannin molecules from Saccharina latissima and Ascophyllum nodosum (a species rich in these compounds) using ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-HRMS2). Water and ethanol (30 and 80% v/v) were used at solid:liquid ratios, extraction times and temperatures, proposed to result in high TPC in extracts from other species. The S. latissima extracts, however, did not allow phlorotannin detection by either UHPLC-UV/Vis or UHPLC-HRMS2, despite a TPC response by the Folin-Ciocalteu assay, pinpointing a problem with interference by non-phenolic compounds. Purification by solid phase extraction (SPE) led to purer, more concentrated fractions and identification of four phlorotannin species in A. nodosum and one in S. latissima by UHPLC-HRMS2, using extracts in ethanol 80% v/v at a solid:liquid ratio of 1:10 for 20 h at 25 °C with an added 10 h at 65 °C incubation of remaining solids. The phlorotannin with the formula C12H10O7 (corresponding to bifuhalol) is the first identified in S. latissima

Investigating lignin-derived monomers and oligomers in low-molecular-weight fractions separated from depolymerized black liquor retentate by membrane filtration

Base-catalyzed depolymerization of black liquor retentate (BLR) from the kraft pulping process, followed by ultrafiltration, has been suggested as a means of obtaining low-molecular-weight (LMW) compounds. The chemical complexity of BLR, which consists of a mixture of softwood and hardwood lignin that has undergone several kinds of treatment, leads to a complex mixture of LMW compounds, making the separation of components for the formation of value-added chemicals more difficult. Identifying the phenolic compounds in the LMW fractions obtained under different depolymerization conditions is essential for the upgrading process. In this study, a state-of-the-art nontargeted analysis method using ultra-high-performance supercritical fluid chromatography coupled to high-resolution multiple-stage tandem mass spectrometry (UHPSFC/HRMSn ) combined with a Kendrick mass defect-based classification model was applied to analyze the monomers and oligomers in the LMW fractions separated from BLR samples depolymerized at 170–210◦ C. The most common phenolic compound types were dimers, followed by monomers. A second round of depolymerization yielded low amounts of monomers and dimers, while a high number of trimers were formed, thought to be the result of repolymerization