@phdthesis{HafergebZailer2021,
  author    = {Hafer [geb. Zailer], Elina},
  title     = {Tagging - Development of new qNMR methods},
  doi       = {10.25972/OPUS-21958},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219583},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {High-resolution nuclear magnetic resonance (NMR) spectroscopy is used in structure elucidation and qualitative as well as quantitative examination of product components. Despite the worldwide development of numerous innovative NMR spectroscopic methods, several official methods that analyze specific substances and do not represent a holistic analysis, are still in use for the quality control of drugs, food and chemicals. Thus, counterfeit or contaminated products of inferior quality can be brought onto the market and distributed despite previous quality controls. To prevent this, three NMR spectroscopic methods have been developed within the scope of this work (1) to study the peroxide value in vegetable and animal oils, (2) for the qualitative and quantitative analysis of metal cations and (3) to determine the enantiomeric excess in chiral alcohols. In oil analysis, titration methods are used to determine the bulk quality parameters such as peroxide value, which represents the concentration of peroxides. Titrations show several drawbacks, such as the need of a large amount of sample and solvents, cross reactions and the low robustness. Thus, an alternative NMR spectroscopic method was developed to improve the peroxide analysis by using triphenylphosphine as a derivatization reagent, which reacts with peroxides in a stoichiometric ratio of 1:1 forming triphenylphosphine oxide. In the 1H-31P decoupled NMR spectrum, the signals of the unreacted triphenylphosphine and the reacted triphenylphosphine oxide are detected at 7.4 ppm and 7.8 ppm, respectively. The ratio of the two signals is used for the calculation of the peroxide concentration. 108 oil samples with a peroxide value between 1 meq/kg and 150 meq/kg were examined using the developed method. Oils with a very low peroxide value of less than 3 meq/kg showed a relative standard deviation of 4.9\%, highly oxidized oils with a peroxide value of 150 meq/kg of 0.2\%. The NMR method was demonstrated as a powerful technique for the analysis of vegetable and krill oils. Another 1H NMR spectroscopic method was developed for the qualitative determination of Be2+, Sr2+ and Cd2+, and for the qualitative and quantitative determination of Ca2+, Mg2+, Hg2+, Sn2+, Pb2+ and Zn2+ by using ethylenediamine tetraacetate (EDTA) as complexing agent. EDTA is a hexadentate ligand that forms stable chelate complexes with divalent cations. The known amount of added EDTA and the signal ratio of free and complexed EDTA are used to calculate the concentrations of the divalent cations, which makes the use of an internal standard obsolete. The use of EDTA with Be2+, Sr2+, Cd2+, Ca2+, Mg2+, Hg2+, Sn2+, Pb2+ and Zn2+ result in complexes whose signals are pH-independent, showing cation-specific chemical shifts and couplings in the 1H NMR spectrum that are used for identification and quantification. In the presented NMR method, the limit of quantification of the cations Ca2+, Mg2+, Hg2+, Sn2+, Pb2+, and Zn2+ was determined with 5-22 μg/mL. This method is applicable in the food and drug sectors. The third NMR spectroscopic method introduced an alternative determination of the enantiomer excess (ee) of the chiral alcohols menthol, borneol, 1-phenylethanol and linalool using phosgene as a derivatizing reagent. Phosgene reacts with a chiral alcohol to form carboxylic acid diesters, made of two identical (RR, SS) or two different enantiomers (RS, SR). These two different types of diastereomers can be examined by the difference of their chemical shifts. In the presented method, the integration values of the carbonyl signals in the 13C NMR spectrum are used for the determination of the enantiomer excess. The limit of quantification depends, among others, on the sample and on the non-labelled or 13C-labelled phosgene used for the analysis. In the case of menthol, a quantification limit of ee=99.1\% was determined using non-labelled phosgene and ee=99.9\% using 13C-labelled phosgene. The 13C NMR method was also applied for the quality control of the enantiomeric purity of borneol, 1-phenylethanol and linalool. The developed 13C NMR method represents a powerful alternative to Mosher's reagent for investigating the enantiomeric excess in chiral alcohols. This work demonstrates the variety of possibilities of applications for the quantitative nuclear magnetic resonance spectroscopy in the chemical analysis of drugs, food and chemicals using tagging reactions such as derivatizations and complexations. The nuclear resonance spectroscopic methods developed in this research work represent powerful alternatives to the previously used quality control techniques.},
  subject      = {NMR Spektroskopie},
  language  = {en}
}
@phdthesis{Pawellek2021,
  author    = {Pawellek, Ruben},
  title     = {Charged Aerosol Detector Performance Evaluation and Development of Optimization Strategies for the Analysis of Amino Acids},
  doi       = {10.25972/OPUS-24319},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-243197},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {The charged aerosol detector (CAD) is an aerosol-based detector employed in liquid chromatography which has become established in the field of pharmaceutical analysis due to its outstanding performance characteristics, e.g. the almost uniform response for nonvolatile analytes. Owing to its principle of detection, the response of the CAD depends on the volatility of a compound and is inherently nonlinear. However, the newly implemented instrumental settings evaporation temperature and power function value (PFV) are valuable tools to overcome some of these drawbacks and can even enhance the detector's capabilities when adjusted properly. This thesis aimed to evaluate the impact of the new instrumental settings on the CAD performance. Additionally, the influence of modern separation techniques for small polar compounds on the CAD was assessed and the applicability of hyphenated UV-CAD techniques explored. The optimization strategies derived from the evaluation procedures and the conjunction of the instrumental and chromatographic techniques investigated were utilized for the challenging impurity profiling of amino acids and amino acid-like drugs. The results of the method validation procedures confirmed the broad applicability of the CAD in the pharmaceutical analysis of nonvolatile compounds, supported by satisfactory sensitivity and reproducibility for meeting the regulatory requirements with respect to the ICH guidelines Q2(R1) and Q3A(R2). The limits of applicability include the analysis of semivolatile compounds, and the method transfer between current and legacy CAD models. Further advances in the definition and standardization of allowed ranges for the instrumental settings and the establishment of general optimization procedures in the method development could lead to a more widespread use of the detection technique in compendial methods.},
  subject      = {Instrumentelle Analytik},
  language  = {en}
}
@phdthesis{Hoellein2015,
  author    = {H{\"o}llein, Ludwig},
  title     = {Entwicklung vereinfachter fl{\"u}ssigchromatographischer 
Untersuchungsmethoden zur Qualit{\"a}tskontrolle essentieller Antimalaria-Medikamente in Entwicklungs- und 
Schwellenl{\"a}ndern},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-113194},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {Im Rahmen dieser Arbeit wurden sehr einfache, fl{\"u}ssigchromatographische Methoden zur Qualit{\"a}tsanalytik gebr{\"a}uchlicher Antimalaria-Medikamente (Amodiaquin, Mefloquin, Proguanil sowie die Kombination Artemether/Lumefantrin) entwickelt, die nur wenige, g{\"u}nstig erh{\"a}ltliche Chemikalien (Phosphatpuffer, Methanol) sowie gew{\"o}hnliche, kommerzielle RP-18-S{\"a}ulen ben{\"o}tigen. Sie sind insbesondere zur Anwendung in Laboratorien in Entwicklungsl{\"a}ndern geeignet und erfordern keine komplexen HPLC-Instrumente wie beispielsweise Gradientenpumpen oder S{\"a}ulenthermostate. Der Verzicht auf Ionenpaarreagenzien erm{\"o}glicht es, dass eine station{\"a}re Phase f{\"u}r mehr als nur einen einzigen Einsatzzweck verwendet werden kann und dass langwierige {\"A}quilibrier- bzw. Sp{\"u}lschritte nicht notwendig sind. Alle Methoden arbeiten im isokratischen Elutionsmodus und durch die Verwendung kurzer S{\"a}ulen (125 mm) konnten die jeweiligen Analysenzeiten zus{\"a}tzlich verringert werden. Hierdurch ist zudem eine Reduzierung des Fließmittelverbrauches m{\"o}glich. W{\"a}hrend der Methodenentwicklung wurden charakteristische, aus dem Herstellungsweg des jeweiligen Arzneistoffes stammende potentielle Verunreinigungen ber{\"u}cksichtigt. Ihre Bestimmung erlaubt eine Aussage {\"u}ber die Herkunft eines Wirkstoffes bzw. eines Arzneimittels, da das Verunreinigungsmuster einer Substanz oftmals die Zuordnung zu einem bestimmten Herstellungs- bzw. Reinigungsprozess erm{\"o}glicht. Alle Methoden wurden hinsichtlich der Linearit{\"a}t innerhalb des Arbeitsbereiches sowie der Wiederholpr{\"a}zision charakterisiert. Es wurde eine gute Reproduzierbarkeit gefunden. Die Nachweis- und Bestimmungsgrenzen der untersuchten Verunreinigungen lagen bei einem Level von je 0.1 \%. Durch gezielte Variation wurde der Einfluss wechselnder Trenntemperaturen sowie schwankender pH-Werte der jeweiligen mobilen Phase und die hieraus resultierenden Effekte untersucht. Hierbei zeigte sich, dass die Methoden sehr robust gegen{\"u}ber diesen Einflussgr{\"o}ßen sind und somit f{\"u}r die Anwendung mit einfach ausgestatteten HPLC-Systemen sowie besonders f{\"u}r den Einsatz in tropische Gebieten mit wechselnden klimatischen Bedingungen gut geeignet sind. Fl{\"u}ssigchromatographische Methoden spielen heute in der pharmazeutischen Analytik vor allem zur Bestimmung der Reinheit eines Arzneistoffes eine herausragende Rolle und sind in nahezu jeder Monographie der wichtigsten Arzneib{\"u}cher (z. B. im Ph. Eur.) zu finden. Einfach durch-f{\"u}hrbare Untersuchungsmethoden, wie beispielsweise die im GPHF-Minilab® angewandte D{\"u}nnschichtchromatographie, erfordern im Vergleich zur HPLC weniger komplexe und teure Instrumente und k{\"o}nnen selbst in entlegenen Gebieten ohne Laboratorium durchf{\"u}hrt werden. Sie verf{\"u}gen allerdings {\"u}ber eine nur sehr geringe Genauigkeit und Reproduzierbarkeit, da sowohl die praktische Durchf{\"u}hrung als auch die anschließende Auswertung rein manuell bzw. visuell erfolgt und somit in hohem Maße einer Beeinflussung durch den jeweiligen Analytiker unterworfen ist. Die entwickelten HPLC-Methoden wurden mit d{\"u}nnschichtchromatographischen Verfahren verglichen, hierbei besonders unter dem Aspekt der visuellen und der instrumentellen Auswertung der Chromatogramme zur Bestimmung des Gehaltes einer unbekannten Probe. Hierbei konnte aufgezeigt werden, dass die D{\"u}nnschichtchromatographie der Fl{\"u}ssigchromatographie eindeutig unterlegen ist, insbesondere wenn die Auswertung nicht mittels eines entsprechenden Scanners sondern rein visuell erfolgt: Nur in den wenigsten F{\"a}llen ist es m{\"o}glich, eine ann{\"a}hernd pr{\"a}zise Aussage {\"u}ber den Gehalt zu treffen und zudem ist die Bestimmung der Verwandten Substanzen nur sehr bedingt m{\"o}glich. Durch den Einsatz von Auftrageger{\"a}ten bzw. Plattenscannern kann die Genauigkeit zwar signifikant erh{\"o}ht werden, allerdings sind solche Instrumente im Verh{\"a}ltnis wesentlich teurer als einfache, modulare HPLC-Systeme und z{\"a}hlen heute in den wenigsten Laboratorien zum Standardinventar. Vereinfachte chromatographische Methoden k{\"o}nnen ein wichtiges Hilfsmittel f{\"u}r Kontrolllaboratorien in Entwicklungsl{\"a}ndern sein, wenn komplexe, etablierte Protokolle nur eingeschr{\"a}nkt angewendet werden k{\"o}nnen. Durch die Kombination aus d{\"u}nnschichtchromatographischer Basisanalytik und einer fl{\"a}chendeckenden Untersuchung mittels HPLC l{\"a}sst sich die Arzneimittelqualit{\"a}t sehr gut {\"u}berpr{\"u}fen, die regulatorischen Organe eines Landes entsprechend zu entlasten und die Versorgung der Bev{\"o}lkerung mit qualitativ einwandfreien Medikamenten zu gew{\"a}hrleisten. Ein weiterer Teil der Arbeit befasst sich mit der Stabilit{\"a}tsanalytik individuell hergestellter, Noradrenalin-haltiger Injektionsl{\"o}sungen. Solche Rezepturen werden oftmals in Krankenhausapotheken im Rahmen der Defektur auf Vorrat durch Verd{\"u}nnen der entsprechenden kommerzieller Fertigarzneimittel mit isotonischer Kochsalzl{\"o}sung zubereitet, um z. B. f{\"u}r Notfallsituationen am Wochenende die Rezepturen vorr{\"a}tig zu haben. Durch die Untersuchungen wurde gepr{\"u}ft, inwieweit der {\"u}bliche Verd{\"u}nnungsgrad von 0.1 \% einen Einfluss auf die Stabilit{\"a}t des Noradrenalins hat und welche Lagerungsbedingungen f{\"u}r die Zubereitungen empfohlen werden k{\"o}nnen. Nach der Lagerung unter verschiedenen Bedingungen (gek{\"u}hlt, bei Raumtemperatur sowie jeweils mit bzw. ohne Lichtschutz) konnte gezeigt werden, dass die Gehalte an Noradrenalin bei keiner der untersuchten Lagerungsbedingungen unter einen Wert von 99.0 \% fielen. Individuell hergestellte Noradrenalin-Injektionsl{\"o}sungen k{\"o}nnen somit bis zu sieben Tage im Voraus hergestellt und f{\"u}r die Anwendung am Patienten bereit gehalten werden. Die L{\"o}sungen sollten dennoch gek{\"u}hlt und unter Lichtschutz aufbewahrt werden, um den Abbau des Arzneistoffes und eine mikrobielle Kontamination zu minimieren.},
  subject      = {HPLC},
  language  = {de}
}
@phdthesis{JakobRodamer2014,
  author    = {Jakob-Rodamer, Verena},
  title     = {Development and validation of LC-MS/MS methods to determine PK/PD parameters of anti-infectives},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-109215},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2014},
  abstract  = {In the present thesis the development and validation of bioanalytical LC-MS/MS methods for the quantification of erythromycin A, erythromycin ethylsuccinate, roxithromycin, clarithromycin, 14 hydroxy clarithromycin, flucloxacillin, piperacillin and moxifloxacin in human plasma and human urine (piperacillin) is introduced. All methods were applied to analyze human plasma and urine samples from clinical trials and therefore, have been validated according to international guidelines. The methods were reliable in these studies and fulfilled all regulatory requirements known at the time of the study conduct. Moreover, the validation data of the macrolides were compared on three different mass spectrometers (API III Plus, API 3000™, API 5000™). The new innovations in the ion source (horizontal versus vertical electrospray), the ionpath (skimmer, QJet) and the diameter of the orifice resulted in better sensitivity and a larger linearity range for the majority of the analytes. Sensitivity was improved up to a factor of 12 (for clarithromycin) between API III Plus to API 3000™ and up to a factor of 8 (for erythromycin and roxithromycin) between API 3000™ and API 5000™, keeping the accuracy and precision data at about the same level. The high sensitivity was a benefit for example for the flucloxacillin study, because concentrations from all subject samples were detectable up to approximately eight half-lives, i.e. no concentrations needed to be reported below the quantification limit. Also the linearity range were extended from two orders of magnitude to up to four orders of magnitude, which increases the likelihood to allow to analyze all samples from a pharmacokinetic study in the same run. This is especially useful if a large concentration range needs to be analysed, for example, if the method shall be applied in an ascending dose study. Then, all low concentrations from the beginning of the study can be determined, as well as all high concentrations, without the need to dilute and analyse single samples repeatedly. The pharmacokinetic data were compared to previously reported literature data and correlated graphically with MIC values of popular microorganisms which might be a starting point for further PK/PD investigations. The PK/PD theory is a very helpful tool for prediction of the efficacy of given drugs against certain micro-organisms. Depending on the pharmacodynamic processes, e. g. the mode of action, three classes of drugs have been identified. In the same way this applies to adverse effects, which need to be minimised by reducing plasma concentrations. These coherences are not well-investigated, yet, and are not discussed further in this thesis. Still, a lot of research has to be done in this interdisciplinary field to minimise uncertainty in single values, like an AUC/MIC. These include: Improve accuracy and precision of bioanalytical methods determining total and free concentration data in biological matrices for calculation of AUC and Cmax These parameters are related to the MIC in pharmacodynamic considerations. Since the determination of the MIC often underlies significant variations and also differences between microbiological laboratories, the determination of concentrations of anti-infectives is particular important, being achievable by scientific exact techniques. Finally, from the volume of distribution of antibiotics can be used to derive information about intracellular concentrations and effectivity of antiinfectives.},
  subject      = {Antimikrobieller Wirkstoff},
  language  = {en}
}
@phdthesis{Leistner2023,
  author    = {Leistner, Adrian Dieter},
  title     = {Improving the quality analysis of monographed drugs - dapsone, baclofen, acarbose and other selected APIs},
  doi       = {10.25972/OPUS-30331},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-303318},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {All presented studies aimed on the improvement of the quality analysis of already monographed drugs. Thereby different LC methods were applied and coupled to i.e., the UV/VIS detector, the CAD or a hyphenation of these detectors, respectively. The choice of the chromatographic system including the detector was largely dependent on the physicochemical properties of the respective analytes. With the risk-assessment report on the API cetirizine we presented an exemplary tool, that can help to minimize the risk of the occurrence of unexpected impurities. An in- deep analysis of each step within synthesis pathway by means of reaction matrices of all compounds was performed. It is essential to understand the complete impurity profile of all reactants, solvents, and catalysts and to include them in the matrix. Finally, the API of this synthesis was checked if all impurities are identified by this tool. Of note, a shortcoming of such a targeted approach is that impurities can still occur, but they are not captured. This disadvantage can be partially compensated by non-targeted approaches if they are performed in parallel with the other studies that represent most of the impurities. However, this work also shows that even in a supposedly simple synthesis, potentially hundreds of by-products can be formed. For each of them, it must be decided individually whether their formation is probable or how their quantity can be minimized in order to obtain APIs, that are as pure as possible. In the dapsone project it was aimed to replace the existing old Ph. Eur. TLC method with a modern RP-HPLC method. This was successful and since Ph. Eur. 10.6, the method developed in this work, became a valid monograph. Within the revision process of the monograph, the individual limits for impurities were tightened. However, this new method needs HPLC instrumentation, suitable to perform gradients. As this is not always available in all control laboratories, we also developed an alternative, more simple method using two different isocratic runs for the impurity analysis. The obtained batch results of both, the new pharmacopoeial method and the more simple one, were in a comparable order of magnitude. Furthermore, within the method development stage of the Ph. Eur. method, we could identify one unknown impurity of the impurity reference by high-resolution MS/MS analysis. Also, in the baclofen project it was aimed to replace the existing Ph. Eur. method with the introduction of an additional impurity to be quantified. A corresponding method was developed and validated. However, due to the harmonization process of the pharmacopoeias, it is currently not used. In addition, we tried to find further, non- 116 SUMMARY chromophoric impurities by means of the CAD. However, except for one counterion of an impurity, no further impurities were found. Also, the aforementioned new impurity could not be detected above the reporting threshold in the batches analyzed. As the only individually specified impurity A is also present at a low level, it can be concluded that the examined batches of baclofen are very pure. The use of universal detectors, such as the CAD can be particularly interesting for compounds with no chromophore or those with only a weak chromophore. Therefore, we decided to take a closer look at the impurity profile of acarbose. Currently, acarbose and its impurities are being studied by low wavelength UV detection at 210 nm. Therefore, the question arose whether there are no other impurities in the API that do not show absorption at this wavelength. CAD, which offers consistent detection properties for all non-volatile compounds, is ideally suited for this purpose. However, it was not so easy to use the CAD together with the UV detector, for example, as a hyphenated detection technique, because the Ph. Eur. method uses phosphate buffers. However, this is non-volatile and therefore inappropriate for the CAD. Therefore, an attempt was made to replace the buffer with a volatile one. However, since this did not lead to satisfactory results and rather the self-degradation process of the stationary phase used could be observed by means of the CAD, it was decided to switch to alternative stationary phases. A column screening also revealed further difficulties with acarbose and its impurities: they show an epimerization reaction at the end of the sugar chain. However, since one wanted to have uniform peaks in the corresponding chromatograms, one had to accelerate this reaction significantly to obtain only one peak for each component. This was best achieved by using two stationary phases: PGC and Amide-HILIC. Impurity-profiling methods could be developed on each of the two phases. In addition, as expected, new impurities could be detected, albeit at a low level. Two of them could even be identified by spiking experiments as the sugar fragments maltose and maltotriose. Taken together, it can be concluded, that this work has contributed significantly to the improvement of the quality analysis of monographed drugs. In addition to the presented general tool for the identification of potential impurities, one of the methods developed, had already been implemented to the Ph. Eur. In an effort to improve the CAD's universal detection capabilities, additional methods have also been developed. Further, new improved methods for the impurity profiling are ready to use.},
  subject      = {Instrumentelle Analytik},
  language  = {en}
}
@article{SalgarellaZahoranovaŠramkovaetal.2018,
  author    = {Salgarella, Alice Rita and Zahoranov{\´a}, Anna and Šr{\´a}mkov{\´a}, Petra and Majerč{\´i}kov{\´a}, Monika and Pavlova, Ewa and Luxenhofer, Robert and Kronek, Juraj and Lac{\´i}k, Igor and Ricotti, Leonardo},
  title     = {Investigation of drug release modulation from poly(2-oxazoline) micelles through ultrasound},
  series = {Scientific Reports},
  volume    = {8},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-018-28140-3},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-227277},
  pages     = {9893, 1-13},
  year      = {2018},
  abstract  = {Among external stimuli used to trigger release of a drug from a polymeric carrier, ultrasound has gained increasing attention due to its non-invasive nature, safety and low cost. Despite this attention, there is only limited knowledge about how materials available for the preparation of drug carriers respond to ultrasound. This study investigates the effect of ultrasound on the release of a hydrophobic drug, dexamethasone, from poly(2-oxazoline)-based micelles. Spontaneous and ultrasound-mediated release of dexamethasone from five types of micelles made of poly(2-oxazoline) block copolymers, composed of hydrophilic poly(2-methyl-2-oxazoline) and hydrophobic poly(2-n-propyl-2-oxazoline) or poly(2-butyl-2-oxazoline-co-2-(3-butenyl)-2-oxazoline), was studied. The release profiles were fitted by zeroorder and Ritger-Peppas models. The ultrasound increased the amount of released dexamethasone by 6\% to 105\% depending on the type of copolymer, the amount of loaded dexamethasone, and the stimulation time point. This study investigates for the first time the interaction between different poly(2-oxazoline)-based micelle formulations and ultrasound waves, quantifying the efficacy of such stimulation in modulating dexamethasone release from these nanocarriers.},
  language  = {en}
}
@phdthesis{Schmidt2023,
  author    = {Schmidt, Sebastian},
  title     = {A closer look at long-established drugs: enantioselective protein binding and stability studies},
  doi       = {10.25972/OPUS-34594},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-345945},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {The aim of this work was to investigate older, established drugs. The extent of the protein binding of chiral ephedra alkaloids to AGP and of ketamine to albumin was determined. Since enantiomers of these drugs are individual available, the focus was on possible enantioselective binding and structural moieties involved in the binding. Previously published work suggested that ephedrine and pseudoephedrine can bind stereoselectively to proteins other than albumin in serum. For the determination of the extent of protein binding, the established ultrafiltration with subsequent chiral CE analysis was used. To determine the influence of basicity on binding, the drugs methylephedrine and norephedrine were also analyzed. Drug binding to AGP increased with increasing basicity as follows: norephedrine < methylephedrine < ephedrine < pseudoephedrine. pKaff was determined both graphically using the Klotz plot and mathematical indicating a low affinity of the ephedra alkaloids to AGP. Using STD-NMR spectroscopy experiments the aromatic protons and the C-CH3 side chain were shown to be most strongly involved in binding, which could be confirmed by molecular docking experiments in more detail. For all drugs, van der Waals-, π π , cationic interactions, hydrogen bonds, and a formation of a salt bridge were observed. The individual enantiomers showed no significant differences and thus the binding of ephedra alkaloids to AGP is not significant. In contrast to the ephedra alkaloids, the possible enantioselective binding to albumin was investigated for R and S ketamine. Again, ultrafiltration followed by CE analysis was performed. The binding of ketamine to one main binding site could be identified. A non-linear fit was used for the determination of pKaff. Using the NMR methods STD-NMR, waterLOGSY-NMR, and CPMG-NMRspectroscopy: the aromatic protons as well as the protons of the NCH3 methyl group showed the largest signal intensity changes, while the cyclohexanone protons showed the smallest changes. pKaff was also determined by the change in the chemical shift at different drug-protein ratios. These obtained values confirm the values obtained from ultrafiltration. Based on this, ketamine is classified as a low-affinity ligand to albumin. There were no significant differences between the individual enantiomers and thus the binding of ketamine to albumin is not a stereoselective process. Using statistical design of experiments an efficient chiral CE method for determining the extent of protein binding of R and S ketamine to albumin was developed and validated according to ICH Q2 (R1) guideline. The stability of ketamine was also investigated because a yellowish discoloration of an aqueous solution of ketamine developed under heat. XRPD investigations showed the same crystal structure for all batches examined. An untargeted screening using LC HRMS as well as LC UV measurements showed no degradation of ketamine or the presence of impurities in stress and non-stressed ketamine solutions, confirming the stability of ketamine under the stress conditions investigated. The lower the quality of the water used in the stress tests, the more intense the yellow discoloration occurred. The impurity or the mechanism that causes the yellow discoloration could not be identified.},
  subject      = {Proteinbindung},
  language  = {en}
}
@phdthesis{Bach2017,
  author    = {Bach, Tobias},
  title     = {Electromechanical interactions in lithium-ion batteries: Aging effects and analytical use},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-153325},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {In the first part of his work, the causes for the sudden degradation of useable capacity of lithium-ion cells have been studied by means of complementary methods such as computed tomography, Post-Mortem studies and electrochemical analyses. The results obtained point unanimously to heterogeneous aging as a key-factor for the sudden degradation of cell capacity, which in turn is triggered by differences in local compression. At high states of health, the capacity fade rate is moderate but some areas of the graphite electrode degrade faster than others. Still, the localized changes are hardly noticeable on cell level due to averaging effects. Lithium plating occurs first in unevenly compressed areas, creating patterns visible to the human eye. As lithium plating leads to rapid consumption of active lithium, a sudden drop in capacity is observed on cell level. Lithium plating appears to spread out from the initial areas over the whole graphite electrode, quickly consuming the remaining useful lithium and active graphite. It can be hypothesized that a self-amplifying circle of reciprocal acceleration of local lithium loss and material loss causes rapid local degradation. Battery cell designers can improve cycle life by homogeneous pressure distribution in the cell and using negative active materials that are resilient to elevated discharge potentials such as improved carbons or lithium titanate. Also, a sufficiently oversized negative electrode and suitable electrolyte additives can help to avoid lithium plating. When packs are designed, care must be taken not to exert local pressure on parts of cells and to avoid both very high and low states of charge. In the second part of this dissertation the resilience of cylindrical and pouchbag cells to shocks and different vibrations was investigated. Stresses inflicted by vibration and shock tests according to the widely recognized UN38.3 transport test were compared to a long-time test that exposed cells to a 186 days long ordeal of sine sweep vibrations with a profile based on real-world applications. All cells passed visual and electric inspection performed by TU M{\"u}nchen after the vibration tests. Only cylindrical cells subjected to long-term vibrations in axial direction showed an increase in impedance and a loss of capacity that could be recuperated in part. The detailed analyses presented in this thesis gave more details on the damages inflicted by vibrations and shocks and revealed drastic damages in some cases. In cylindrical cells, only movement in axial direction caused damage. Long term vibrations were found to be especially detrimental. No damage whatsoever could be detected for pouch cells, regardless of the test protocol and the direction of movement. The extreme resilience of pouchbag cells shows that the electrode stack of lithium-ion cells is resistant to vibrations, and that damages are caused by design imperfections that can be improved at low cost. The findings of this work, and the general state of research show that it is most crucial to control the lithiation and thus potential of the graphite electrode. In the last part of this work, a new, direct method for charge estimation based on changing transmission is presented. A correlation between transmission of short ultrasonic pulses and state of charge is found. This new technology allows direct measurement of the state of charge. The method is demonstrated for batteries with different positive active materials, showing its versatility. As the observed changes can be traced to the lithiation of graphite, it can be determined without a reference electrode. Already at this early stage of development, the found correlations allow estimation of state of charge. The present hysteresis in the signal height of the slow wave, which is unneglectable especially during discharging at higher currents, will be subject to further investigation. The observed effects can be explained by effects on different length scales. Biot's theory explains the second wave's slowness based on the active material particles size in the range of 0.01 mm and electrolyte-filled pores. Lithiation of graphite changes the porosity of the electrode and thereby the velocity and wavelength of the impulse. When the wavelength approaches the length scale of the layers, 0.1 mm, scattering effects dampen the transmitted signal. Finally, the wavelength of the pulse should be shorter than the transducers diameter to obtain a homogeneous wave front. To conclude, the new method allows the control of each individual cell in a pack independent from the electrical connections of the cells. As the method shows great promise, further studies regarding factors such as long-term behavior, temperature and current rates should be conducted. In this thesis hysteresis was observed and a deeper understanding of the reasons behind it may allow further improvements of measurement precision.},
  subject      = {Lithium-Ionen-Akkumulator},
  language  = {en}
}
@phdthesis{Vogg2023,
  author    = {Vogg, Nora Johanna},
  title     = {Mass spectrometry-based quantification of steroids for the diagnostic workup of adrenal tumors},
  doi       = {10.25972/OPUS-29343},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293438},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Tumors of the adrenal gland belong to the most frequent neoplasms in humans with a prevalence of 3-10 \% in adults. The aim of the diagnostic workup is the identification of potentially hormone-secreting and / or malignant tumors, because most of these tumors will require surgical resection. Malignant adrenocortical carcinomas (ACC) are very rare and associated with a poor prognosis in advanced stages, therefore, an early and accurate diagnosis is crucial. Within this thesis, two liquid chromatography tandem mass spectrometry (LC-MS/MS) methods for the quantification of steroids in different biomaterials were developed to improve the diagnostic workup of adrenal tumors. First, an LC-MS/MS method for the simultaneous quantification of cortisol and dexamethasone in serum samples after dexamethasone suppression test (DST) was developed, validated, and applied to 400 clinical samples. Newly established method-specific threshold concentrations for cortisol and dexamethasone increased DST specificity from 67.5 \% to 92.4 \% while preserving 100 \% sensitivity. Second, an LC-MS/MS method for the quantification of eleven urinary steroids was developed and validated to improve the differentiation between ACC and adrenocortical adenomas (ACA). A decision tree requiring only two steroids was trained for classification and tested based on 24 h urine samples from 268 patients with adrenal tumor. Malignancy was excluded with a negative predictive value of 100 \% in an independent validation cohort of 84 samples of 24-h urine. A newly proposed simplified diagnostic workflow with urinary steroid profiling as first tier test could obviate additional adrenal-specific imaging in 42 of 64 patients with ACA. The new DST method is already in clinical use at the University Hospital W{\"u}rzburg, whereas the classification model based on urinary steroid profiling will require prospective validation in a larger cohort.},
  subject      = {Nebennierentumor},
  language  = {en}
}