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When optimizing the process parameters of the acidic ethanolic organosolv process, the aim is usually to maximize the delignification and/or lignin purity. However, process parameters such as temperature, time, ethanol and catalyst concentration, respectively, can also be used to vary the structural properties of the obtained organosolv lignin, including the molecular weight and the ratio of aliphatic versus phenolic hydroxyl groups, among others. This review particularly focuses on these influencing factors and establishes a trend analysis between the variation of the process parameters and the effect on lignin structure. Especially when larger data sets are available, as for process temperature and time, correlations between the distribution of depolymerization and condensation reactions are found, which allow direct conclusions on the proportion of lignin's structural features, independent of the diversity of the biomass used. The newfound insights gained from this review can be used to tailor organosolv lignins isolated for a specific application.
N-Nitrosamines have long been identified as a relevant contaminant in potable water due to their identification as probable human carcinogens. Thus, highly sensitive detection of these pollutants in the ultra-trace range is imperative to comply with strict regulatory specifications. To this end, many institutions rely on mass spectrometry-based analysis methods, which have the disadvantage of being cost- and resource intensive. This study aims to develop, optimise, and evaluate a gas chromatography-drift tube-ion mobility spectrometry (GCIMS) based method with a twofold enrichment strategy consisting of solid phase extraction (SPE) followed by intube extraction (ITEX) of the eluate for nine different nitrosamines in drinking water in order to offer a sensitive alternative to the current state of the art. Optimisation of ITEX parameters was successfully performed using a simplex self-directing design approach, so that a calibration range between 5 and 50 ng/L could be achieved. The suitability of a linear regression model was demonstrated via analysis of variance (ANOVA) criteria. The analysis of different spiked drinking water samples allowed for the determination of the method's accuracy (27.3 - 114.5 % across different nitrosamine analytes and matrices, with most above 70 % recovery) and detection limits (1.12 - 12.48 ng/L across different nitrosamine analytes and matrices), which fall within the range of required limit values. Tested drinking waters show innate nitrosamine concentrations well below detection limits and can thus be deemed free from contaminants.
For analysis with liquid chromatography (LC), samples and calibration standards generally require a dilution by a factor of 103 to 106. To guarantee a high accuracy, sample preparation usually employs high-volume pipettes and volumetric flasks for dilution series. Consequently, sample preparation is a prominent driving factor for consumption of solvents in the LC laboratory. Miniaturisation in sample preparation can thus be a means of reducing the required amount of solvent within the laboratory, saving valuable resources. In the context of dilution series, this can be achieved by the use of low-volume dispensing tools, which usually have a higher relative instrument error, resulting in a less accurate overall method. Another approach is the transition to a gravimetric sample preparation, in which the dilution steps are not measured in volume but weight, only depending on the much lower error of the analytical balance. By implementing weighing robots, one can fully automate the sample preparation workflow. This study deals with the comparison of various dilution methods. Gravimetric, robot-aided dilution allows for the reduction of the solvent down to the amount of sample needed for analyses. Including the initial dissolution of the sample, using gravimetric dilution can reliably and repeatedly reduce the required solvent amount by over 90 %, while still generating the same analytical results. Overall, this application leads to significant economic, ecological, social, and technological benefits for the LC laboratory.
Nitrosamines have been identified as a probable human carcinogen and thus are of high concern in many manufacturing industries and various matrices (for example pharmaceutical, cosmetic and food products, workplace air or potable- and wastewater). This study aims to analyse nine nitrosamines relevant in the field of occupational safety using a gas chromatography-drift tube ion mobility spectrometry (GC-DT-IMS) system. To do this, single nitrosamine standards as well as a standard mix, each at 0.1 g/L, were introduced via liquid injection. A GC-DT-IMS method capable of separating the nitrosamine signals according to retention time (first dimension) and drift time (second dimension) in 10 min was developed. The system shows excellent selectivity as each nitrosamine gives two signals pertaining to monomer and dimer in the second dimension. For the first time, reduced ion mobility values for nitrosamines were determined, ranging from 1.18 to 2.03 cm2s−1V−1. The high selectivity of the GC-DT-IMS method could provide a definite advantage for monitoring nitrosamines in different manufacturing industries and consumer products.
Background: Transdermal therapeutic systems use substance transport through the skin to provide an active pharmaceutical ingredient. To ensure a reliable supply, adhesion to skin must be guaranteed. In practice in vivo studies as well as in vitro studies on steel (ISO-standard for self-adhesive tapes) are used. As in vitro—in vivo correlation is poor, extensive in vivo studies are applied during industrial product performance tests. Hence, a specialized skin substitute material for in vitro adhesion testing is needed.
Materials and Methods: Synthetic leather (polyurethane), silicone (Dragon Skin), gelatines, and VitroSkin are used as skin substitute materials. For topographical analysis, reflected light microscopy and confocal light microscopy are applied. Infrared spectroscopy is performed for analysis of functional groups. Dermatological skin probe systems are used to analyze friction, surface pH, and elasticity. To bundle all data with regards to skin similarity, mid-level data fusion is applied.
Results: For all substitute materials, common topographic characteristics compared to human skin can be observed. However, all materials show limitations regarding their topography. Gelatine and VitroSkin feature comparable surface functionality compared to human skin. All materials show significant deficits in their mechanical properties. All characteristics can be summarized as the Skin Similarity Index to give a comprehensive overview regarding substitutes similarity to skin.
Conclusions: A comprehensive evaluation of topography, chemical functionality, and mechanical properties regarding a skin substitutes similarity to human skin was performed. This data should be considered as a baseline for further research in the field of adhesion to skin. By adding further characteristics and materials, it is a versatile approach that can be implemented in a variety of areas.
