TY - GEN A1 - Mix, Renate A1 - Falkenhagen, Jana A1 - Schulze, Rolf-Dieter A1 - Gerstung, Vanessa A1 - Friedrich, Jörg Florian ED - K.L. Mittal, T1 - Plasma homo- and copolymerization of allyl alcohol and styrene KW - Plasma polymerization KW - Surface functionalization KW - Molar masses PY - 2009 SN - 978-90-04-16590-8 VL - 5 SP - 317 EP - 340 PB - Koninklijke Brill NV CY - Leiden, The Netherlands AN - OPUS4-19606 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Advances in characterization of polymer heterogeneity by coupling of chromatographic and spectroscopic methods T2 - International Discussion Meeting, Deutsche Bunsen-Gesellschaft für Physikalische Chemie CY - Mainz, Germany DA - 1999-03-15 PY - 1999 AN - OPUS4-3282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Is Liquid Chromatography at Critical Conditions already a routine technique? T2 - Int. Symp. on GPC/SEC and Related Techniques CY - Frankfurt/Main DA - 2014-09-30 PY - 2014 AN - OPUS4-32000 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Charakterisierung von Polymeren durch Kombination von HPLC und MALDI-TOF-MS T2 - Statusseminar des ACA CY - Berlin, Germany DA - 1996-11-05 PY - 1996 AN - OPUS4-2228 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Moser, Marko A1 - Behnke, Thomas A1 - Hamers-Allin, Carolina A1 - Klein-Hartwig, Karin A1 - Falkenhagen, Jana A1 - Resch-Genger, Ute T1 - Quantification of PEG-maleimide ligands and coupling efficiencies on nanoparticles with Ellman's reagent N2 - The surface modification of nanometer- and micrometer-sized particles and planar substrates with polyethylene glycol (PEG) ligands of varying length is a very common strategy to tune the hydrophilicity and biocompatibility of such materials, minimize unspecific interactions, improve biofunctionalization efficiencies, and enhance blood circulation times. Nevertheless, simple methods for the quantification of PEG ligands are comparatively rare. Here, we present a new concept for the quantification of PEG ligands for maleimide-functionalized PEG molecules and the determination of PEG coupling efficiencies, exploiting the quantitative reaction of maleimide with ʟ-cysteine, and the subsequent determination of the unreacted thiol with the photometric Ellman's test. This is shown for heterobifunctional PEG spacers of varying length and amino-functionalized polystyrene nanoparticles (PS NP) without and with differently charged encoding dyes. The reaction of ʟ-cysteine with the Ellman's reagent was monitored photometrically and with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) to derive the reaction mechanism and to obtain the stoichiometry factor for ʟ-cysteine quantification. Mass balances and quantification of ʟ-cysteine via its sulfur concentration using elemental analysis and inductively coupled plasma mass spectrometry (ICP-MS) confirmed the accuracy and reliability of this approach that can be extended to other surface groups and ligands. KW - Photometric assay KW - Surface analysis KW - Nanoparticle KW - Polyethylene glycol KW - PEG quantification KW - Ellman's test PY - 2015 DO - https://doi.org/10.1021/acs.analchem.5b02173 SN - 0003-2700 SN - 1520-6882 VL - 87 IS - 18 SP - 9376 EP - 9383 PB - American Chemical Society CY - Washington, DC AN - OPUS4-34468 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Liquid Chromatography at Critical Conditions - advantages and shortcomings T2 - Arbeitskreis Polymeranalytik CY - Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF Darmstadt DA - 2015-03-20 PY - 2015 AN - OPUS4-32937 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Characterization of polylactides by coupling of chromatographic methods with MALDI-TOF-MS T2 - ISPAC CY - Enschede, Netherlands DA - 2002-06-17 PY - 2002 AN - OPUS4-3454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Barner‐Kowollik, C. A1 - Falkenhagen, Jana A1 - Gründling, T. A1 - Weidner, Steffen ED - Barner-Kowollik, C. ED - Gründling, T. ED - Falkenhagen, Jana ED - Weidner, Steffen T1 - Introduction N2 - The book opens with an overview of the available mass analyzers. Special consideration is given by the authors Steven Blanksby and Gene Hart-Smith to their uses in polymer chemistry. Various ionization techniques applicable in polymer mass spectrometry are then explored in-depth by Anthony Gies. Chrys Wesdemiotis subsequently takes a close look at tandem mass spectrometry, a highly important tool for the elucidation of polymer structure and one of the major contemporary fields of development in the mass spectrometry sector. Sarah Trimpin and colleagues follow with their contribution, describing gas-phase ion-separation procedures as applied to synthetic polymers. The ionization process of polymers via the MALDI approach requires a careful design of the sample preparation procedures. Scott Hanton and Kevin Owens therefore provide a close look at how polymer samples are best prepared. Synthetic polymers are not only important materials in their own right, but are also frequently employed to (covalently) modify variable surfaces. Surface analysis is notoriously challenging and a range of techniques have to be employed to map the chemical characteristics of surface-bound macromolecules. Christine Mahoney and Steffen Weidner provide a detailed description of the part which surface-sensitive mass spectrometric techniques play in elucidating a polymer surface’s structure. Soft ionization mass spectrometry techniques can be especially powerful when combined with chromatographic techniques such as size exclusion chromatography (SEC), liquid adsorption chromatography at critical conditions (LACCCs) or both. Jana Falkenhagen and Steffen Weidner explore the wide variety of so-called hyphenated techniques and impressively demonstrate the information depth that can be attained by employing such technologies. While arguably the majority of molecular weight determination is carried out via SEC often equipped with refractive index as well as light scattering detectors, Till Gruendling, William Wallace, and colleagues demonstrate how MALDI-MS as well as SEC coupled to ESI-MS can be employed to deduce absolute molecular weight distributions. The chapter also provides an overview of contemporary automated data processing techniques for mass spectrometric data. Most polymers generated are arguably copolymers and it thus is mandatory to dedicate an entire chapter to the analysis of copolymers via mass spectrometry — Ulrich Schubert and Anna Crecelius provide an in-depth analysis. The field of living/controlled radical polymerization provides fascinating high precision avenues for the construction of complex macromolecular architectures and enables the generation of polymers with a high degree of end-group fidelity, which are often employed in cross-discipline applications (e.g., in biosynthetic conjugates). Soft ionization mass spectrometry plays an integral part in unravelling the mechanism of living/controlled radical polymerization processes as well as in the characterization of macromolecular building blocks: Christopher Barner-Kowollik and colleagues take a close look at the current state-of-the-art. Similarly, polymers generated via conventional radical polymerization can be readily investigated via mass spectrometry. Here, especially the investigation of the initiation process and of the generated end-group type is of high importance — Michael Buback, Greg Russell, and colleagues report. Finally, Grazyna Adamus and Marek Kowalczuk survey the field of mass spectrometry applied to polymers prepared via nonradical methods such as coordination polymerization, polycondensation, and polyaddition. The question of polymer stability and a detailed understanding of polymer degradation processes on a molecular level are of paramount importance for an evaluation of the performance of a polymer in chemical applications or as a material. Sabrina Carroccio and colleagues survey the field of soft ionization mass spectrometry applied to the molecular study of degradation processes at the book’s conclusion. KW - Mass spectrometry KW - Polymers PY - 2012 SN - 978-3-527-32924-3 SN - 978-3-527-64182-6 DO - https://doi.org/10.1002/9783527641826.ch SP - 1 EP - 4 PB - Wiley-VCH CY - Weinheim AN - OPUS4-65732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Challenges of SEC and the necessity of round robin tests N2 - Size exclusion chromatography (SEC) is still the method of choice for determining the molar mass and molar mass distribution of macromolecules. It is a liquid chromatographic technique that separates molecules based on their size, respectively their hydrodynamic volume using a porous stationary phase that allows smaller molecules to pass through the pores while excluding larger molecules. The chromatogram from the size separation can be calibrated using polymers of known molar mass resulting in a relative molar mass distribution curve. From this distribution curve molar mass averages and the oligomer content (percentage of peak area smaller than 1000 g/mol and 500 g/mol) of polymers can be derived. The determination of oligomer content is important, because it is often used in regulatory contexts as a measure of small, mobile and potentially more toxic parts of the polymer. Polymer regulations are of increasing political and societal importance. Regulations often strive for narrow limits. But SEC has rather large error margins of 10-20% for the molar mass determination performed in different laboratories or on different instruments. These variances are well known to all experts and users and have been investigated in several round robin tests in the past. These resulted in DIN and ISO standards which, in our opinion, no longer meet today's requirements. Gaps have been identified that require further harmonization. Different polymer types or classes require different methods. On the other hand, as far as we know, the margins of error in determining oligomer content have not yet been investigated. It is expected that the variation will be rather high. This is because it depends on many factors related to the experimental conditions (column sets used, solvent, temperatures, sample preparation) on the one hand, and the data evaluation mechanisms (choice of baseline and peak limits) on the other. In order to actually measure the error margins and to support this with actual data a round robin test has been performed from June to November 2024 with approx. 40 participating laboratories. Three different solvents were selected, namely THF, DMAc or DMF and water. The samples were selected taking into account a wide range of practical aspects far from narrowly distributed standards: e.g higher distribution range, reduced solubility, included side components, copolymers and dispersions with gel content. In this contribution we will present the detailed concept of this round robin test and first impressions. T2 - 11th International Symposium on the Separation and Characterization of Natural and Synthetic Macromolecules CY - Amsterdam, Netherlands DA - 21.01.2025 KW - Size exclusion chromatography KW - Round robin tests PY - 2025 AN - OPUS4-62533 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Falkenhagen, Jana T1 - Error margins in the Determination of Molar Mass and Oligomer Content of Polymers N2 - Size exclusion chromatography (SEC) is still the method of choice for determining the molar mass and molar mass distribution of macromolecules. It is a liquid chromatographic technique that separates molecules based on their size, respectively their hydrodynamic volume using a porous stationary phase that allows smaller molecules to pass through the pores while excluding larger molecules. The chromatogram from the size separation can be calibrated using polymers of known molar mass resulting in a relative molar mass distribution curve. From this distribution curve molar mass averages and the oligomer content (percentage of peak area smaller than 1000 g/mol and 500 g/mol) of polymers can be derived. The determination of oligomer content is important, because it is often used in regulatory contexts as a measure of small, mobile and potentially more toxic parts of the polymer. Polymer regulations are of increasing political and social importance. Regulations often set very narrow limits. SEC has rather large error margins of 10-20% for the molar mass determination performed in different laboratories or on different instruments. These variances are well known to all experts and users and have been investigated in several round robin tests in the past. These resulted in DIN and ISO standards which, in our opinion, no longer meet today's requirements. As far as we know, the margins of error in determining oligomer content have not yet been investigated. It is expected that the variation will be rather high. This is because it depends on many factors related to the experimental conditions (column sets used, solvent, temperatures, sample preparation) on the one hand, and the data evaluation mechanisms (choice of baseline and peak limits) on the other. In order to actually measure the error margins and to support this with actual data a round robin test has been performed from June to November 2024 with approx. 40 participating laboratories. Three different solvents were selected, namely THF, DMAc or DMF and water. The samples were selected together with all the experts, taking into account a wide range of practical aspects far from narrowly distributed standards: e.g higher distribution range, reduced solubility, included side components, copolymers and dispersions with gel content. In this contribution we will present the detailed concept of this round robin test and first results. T2 - SETAC Europe 35th Annual Meeting CY - Vienna, Austria DA - 11.05.2025 KW - Size exclusion chromatography KW - REACH KW - Polymers KW - Round Robin Tests PY - 2025 AN - OPUS4-63307 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Moser, Marko A1 - Schneider, Ralf A1 - Behnke, Thomas A1 - Schneider, Thomas A1 - Falkenhagen, Jana A1 - Resch-Genger, Ute T1 - Ellman’s and aldrithiol assay as versatile and complementary tools for the quantification of thiol groups and ligands on nanomaterials N2 - Simple, fast, and versatile methods for the quantification of thiol groups are of considerable interest not only for protein analysis but also for the characterization of the surface chemistry of nanomaterials stabilized with thiol ligands or bearing thiol groups for the subsequent (bio-) functionalization via maleimide−thiol chemistry. Here, we compare two simple colorimetric assays, the widely used Ellman’s assay performed at alkaline pH and the aldrithiol assay executed at acidic and neutral pH, with respect to their potential for the quantification of thiol groups and thiol ligands on different types of nanoparticles like polystyrene nanoparticles, semiconductor nanocrystals (SC NC), and noble metal particles, and we derive criteria for their use. In order to assess the underlying reaction mechanisms and to obtain stoichiometry factors mandatory for reliable thiol quantification, both methods were studied photometrically and with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), thereby demonstrating the influence of different thiols on the reaction mechanism. Our results underline the suitability of both methods for the quantification of directly accessible thiol groups or ligands on the surface of 2D- and 3D-supports, here exemplarily polystyrene nanoparticles. Moreover, we could derive strategies for the use of these simple assays for the determination of masked (i.e., not directly accessible) thiol groups like disulfides such as lipoic acid and thiol stabilizing ligands coordinatively bound to Cd and/or Hg surface atoms of II/VI and ternary SC NC and to gold and silver nanoparticles. KW - Nanoparticles KW - Ligands KW - Ellman KW - Aldrithiol KW - Quantification PY - 2016 DO - https://doi.org/10.1021/acs.analchem.6b01798 SN - 0003-2700 SN - 1520-6882 VL - 88 IS - 17 SP - 8624 EP - 8631 PB - ACS Publications CY - Washington AN - OPUS4-37561 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -