TY - JOUR A1 - Weidner, Steffen A1 - Knappe, Patrick A1 - Panne, Ulrich T1 - MALDI-TOF imaging mass spectrometry of artifacts in 'dried droplet' polymer samples N2 - Matrix-assisted laser desorption/ionization-timeof-flight (MALDI-TOF) imaging of polystyrenes with various molecular masses was applied to study spatial molecular mass distribution of polymers in sample spots prepared by the 'dried droplet' method. When different solvents and target surfaces were examined, a segregation of single homologous polymers was observed depending upon the evaporation rate of the solvent. For the observed Patterns left by the evaporating droplet, a hypothesis is offered taking into account different hydrodynamic interactions and diffusion. The results illustrate that spot preparation using the conventionally 'dried droplet' method is prone to artifacts and should be avoided for reliable and reproducible MALDI mass spectrometry experiments with regards to the Determination of molecular masses and mass distributions. KW - MALDI KW - Mass spectrometry imaging KW - Polymer KW - Droplet PY - 2011 U6 - https://doi.org/10.1007/s00216-011-4773-1 SN - 1618-2642 SN - 1618-2650 VL - 401 IS - 1 SP - 127 EP - 134 PB - Springer CY - Berlin AN - OPUS4-24538 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leiterer, Jork A1 - Panne, Ulrich A1 - Thünemann, Andreas A1 - Weidner, Steffen T1 - Container-less polymerization in acoustically levitated droplets: an analytical study by GPC and MALDI-TOF mass spectrometry N2 - Molecular masses and end groups of polystyrene (PS) formed in a novel container-less polymerization strategy, based on levitated droplets in an acoustic trap, were determined by Gel Permeation Chromatography (GPC) and Matrix-assisted Laser Desorption/Ionization Time of Flight Mass spectrometry (MALDI-TOF MS). KW - Ultraschallfalle KW - MALDI Massenspektrometrie KW - Polymerisation PY - 2011 U6 - https://doi.org/10.1039/c0ay00390e SN - 1759-9660 SN - 1759-9679 VL - 3 IS - 1 SP - 70 EP - 73 PB - RSC Publ. CY - Cambridge AN - OPUS4-23655 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Benjamin Christoph A1 - Seifert, Stephan A1 - Panne, Ulrich A1 - Kneipp, Janina A1 - Weidner, Steffen T1 - Matrix-assisted laser desorption/ionization mass spectrometric investigation of pollen and their classification by multivariate statistics N2 - RATIONALE A fast and reliable online identification of pollen is not yet available. The identification of pollen is based mainly on the evaluation of morphological data obtained by microscopic methods. METHODS Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) was applied to the analysis of extracts and milled pollen samples. The obtained MALDI data were explored for characteristic peak patterns which could be subjected to a multivariate statistical analysis. RESULTS Two sample preparation methods are presented, which require only minimal or no chemical extraction of the pollen. MALDI pollen spectra could be recorded showing various peak patterns. A multivariate statistics approach allowed the classification of pollen into clusters indicating similarities and differences between various species. CONCLUSIONS These results demonstrate the potential and the reliability of MALDI-TOF MS for the identification and, in combination with multivariate statistics, also for the classification of pollen. KW - MALDI TOF mass spectrometry KW - Pollen KW - Multivariate statistics PY - 2012 U6 - https://doi.org/10.1002/rcm.6202 SN - 0951-4198 SN - 1097-0231 VL - 26 IS - 9 SP - 1032 EP - 1038 PB - Wiley CY - Chichester AN - OPUS4-25648 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gabriel, Stefan A1 - Pfeifer, Dietmar A1 - Schwarzinger, C. A1 - Panne, Ulrich A1 - Weidner, Steffen T1 - Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric imaging of synthetic polymer sample spots prepared using ionic liquid matrices N2 - RATIONALE Polymer sample spots for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) prepared by the dried-droplet method often reveal ring formation accompanied by possible segregation of matrix and sample molecules as well as of the polymer homologs itself. Since the majority of sample spots are prepared by this simple and fast method, a matrix or sample preparation method that excludes such segregation has to be found. METHODS Three different ionic liquid matrices based on conventionally used aromatic compounds for MALDI-TOF MS were prepared. The formation of ionic liquids was proven by 1H NMR spectroscopy. MALDI-Imaging mass spectrometry was applied to monitor the homogeneity. RESULTS Our results show a superior sample spot homogeneity using ionic liquid matrices. Spots could be sampled several times without visible differences in the mass spectra. A frequently observed loss of matrix in the mass spectrometer vacuum was not observed. The necessary laser irradiance was reduced, which resulted in less polymer fragmentation. CONCLUSIONS Ionic liquid matrices can be used to overcome segregation, a typical drawback of conventional MALDI dried-droplet preparations. Homogeneous sample spots are easy to prepare, stable in the MS vacuum and, thereby, improve the reproducibility of MALDI. PY - 2014 U6 - https://doi.org/10.1002/rcm.6810 SN - 0951-4198 SN - 1097-0231 VL - 28 IS - 5 SP - 489 EP - 498 PB - Wiley CY - Chichester AN - OPUS4-30267 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gabriel, Stefan A1 - Schwarzinger, C. A1 - Schwarzinger, B. A1 - Panne, Ulrich A1 - Weidner, Steffen T1 - Matrix segregation as the major cause for sample inhomogeneity in MALDI dried droplet spots N2 - The segregation in dried droplet MALDI sample spots was analyzed with regard to the matrix-to-sample ratio using optical microscopy, MALDI imaging mass spectrometry (MALDI MSI) and IR imaging spectroscopy. In this context, different polymer/matrix/solvent systems usually applied in the analysis of synthetic polymers were investigated. The use of typical matrix concentrations (10 mg mL-1) in almost every case resulted in ring patterns, whereas higher concentrated matrix solutions always led to homogeneous sample spot layers. The data revealed that segregation is predominantly caused by matrix transport in the drying droplet, whereas polymer segregation seems to be only secondary. KW - MALDI KW - Imaging MS KW - Matrix segregation KW - Dried droplet KW - Sample preparation KW - Polymers PY - 2014 U6 - https://doi.org/10.1007/s13361-014-0913-0 SN - 1044-0305 VL - 25 IS - 8 SP - 1356 EP - 1363 PB - American Society for Mass Spectrometry CY - New York, NY AN - OPUS4-32582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gabriel, Stefan A1 - Steinhoff, R.F. A1 - Pabst, M. A1 - Schwarzinger, C. A1 - Zenobi, R. A1 - Panne, Ulrich A1 - Weidner, Steffen T1 - Improved analysis of ultra-high molecular mass polystyrenes in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using DCTB matrix and caesium salts N2 - Rationale The ionization of polystyrenes in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is typically achieved by the use of silver salts. Since silver salts can cause severe problems, such as cluster formation, fragmentation of polymer chains and end group cleavage, their substitution by alkali salts is highly desirable. Methods The influence of various cations (Ag+, Cs+ and Rb+) on the MALDI process of polystyrene (PS) mixtures and high mass polystyrenes was examined. The sample preparation was kept as straightforward as possible. Consequently, no recrystallization or other cleaning procedures were applied. Results The investigation of a polystyrene mixture showed that higher molecular polystyrenes could be more easily ionized using caesium, rather than rubidium or silver salts. In combination with the use of DCTB as matrix a high-mass polymer analysis could be achieved, which was demonstrated by the detection of a 1.1 MDa PS. Conclusions A fast, simple and robust MALDI sample preparation method for the analysis of ultra-high molecular weight polystyrenes based on the use of DCTB and caesium salts has been presented. The suitability of the presented method has been validated by using different mass spectrometers and detectors. KW - MALDI KW - Mega-dalton KW - Ionization KW - Caesium KW - Polystyrene KW - DCTB PY - 2015 UR - http://onlinelibrary.wiley.com/doi/10.1002/rcm.7197/full U6 - https://doi.org/10.1002/rcm.7197 SN - 0951-4198 SN - 1097-0231 VL - 29 IS - 11 SP - 1039 EP - 1046 PB - Wiley CY - Chichester AN - OPUS4-33191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sötebier, Carina A1 - Bierkandt, Frank A1 - Rades, Steffi A1 - Jakubowski, Norbert A1 - Panne, Ulrich A1 - Weidner, Steffen T1 - Sample loss in asymmetric flow field-flow fractionation coupled to inductively coupled plasma-mass spectrometry of silver nanoparticles N2 - In this work, sample losses of silver nanoparticles (Ag NPs) in asymmetrical flow field-flow fractionation (AF4) have been systematically investigated with the main focus on instrumental conditions like focusing and cross-flow parameters as well as sample concentration and buffer composition. Special attention was drawn to the AF4 membrane. For monitoring possible silver depositions on the membrane, imaging laser ablation coupled to inductively coupled plasma mass spectrometry (LA-ICP-MS) was used. Our results show that the sample residue on the membrane was below 0.6% of the total injected amount and therefore could be almost completely avoided at low sample concentrations and optimized conditions. By investigation of the AF4 flows using inductively coupled plasma mass spectrometry (ICP-MS), we found the recovery rate in the detector flow under optimized conditions to be nearly 90%, while the cross-flow, slot-outlet flow and purge flow showed negligible amounts of under 0.5%. The analysis of an aqueous ionic Ag standard solution resulted in recovery rates of over 6% and the ionic Ag content in the sample was found to be nearly 8%. Therefore, we were able to indicate the ionic Ag content as the most important source of sample loss in this study. KW - Asymmetric flow filed-flow fractionation KW - ICP-MS KW - Nanoparticles KW - Sample loss KW - Quantification PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-336171 SN - 0267-9477 SN - 1364-5544 VL - 30 IS - 10 SP - 2214 EP - 2222 PB - Royal Society of Chemistry CY - London AN - OPUS4-33617 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seifert, Stephan A1 - Weidner, Steffen A1 - Panne, Ulrich A1 - Kneipp, Janina T1 - Taxonomic relationship of pollen from MALDI TOF MS data using multivariate statistics N2 - Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been suggested as a promising tool for the investigation of pollen, but the usefulness of this approach for classification and identification of pollen species has to be proven by an application to samples of varying taxonomic relations. KW - MALDI mass spectrometry KW - Pollen KW - Multivariate statistics PY - 2015 U6 - https://doi.org/10.1002/rcm.7207 SN - 0951-4198 SN - 1097-0231 VL - 29 SP - 1145 EP - 1154 PB - Wiley CY - Chichester AN - OPUS4-35296 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sötebier, Carina A. A1 - Weidner, Steffen A1 - Jakubowski, Norbert A1 - Panne, Ulrich A1 - Bettmer, J. T1 - Separation and quantification of silver nanoparticles and silver ions using reversed phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry in combination with isotope dilution analysis N2 - A reversed phase high performance liquid chromatography coupled to an inductively coupled Plasma mass spectrometer (HPLC–ICP-MS) approach in combination with isotope dilution analysis (IDA) for the separation and parallel quantification of nanostructured and ionic silver (Ag) is presented. The main Focus of this work was the determination of the ionic Ag concentration. For a sufficient stabilization of the Ions without dissolving the nanoparticles (NPs), the eluent had to be initially optimized. The determined Ag ion concentration was in a good agreement with results obtained using ultrafiltration. Further, the mechanism of the NP separation in the HPLC column was investigated. Typical size exclusion effects were found by comparing results from columns with different pore sizes. Since the recovery rates decreased with increasing Ag NP size and large Ag NPs did not elute from the column, additional interactions of the particles with the stationary phase were assumed. Our results reveal that the presented method is not only applicable to Ag NPs, but also to gold and polystyrene NPs. Finally, IDA-HPLC-ICP-MS experiments in single particle mode were performed to determine the particle cut-off size. The comparison with conventional spICP-MS experiments resulted in a similar diameter and particle size distribution. KW - ICP-MS KW - Silver nanoparticles KW - Speciation KW - High performance liquid chromatography KW - Isotope dilution analysis PY - 2016 U6 - https://doi.org/10.1016/j.chroma.2016.09.028 SN - 0021-9673 VL - 1468 SP - 102 EP - 108 AN - OPUS4-37652 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sötebier, Carina A1 - Weidner, Steffen A1 - Jakubowski, Norbert A1 - Panne, Ulrich A1 - Bettmer, J. T1 - Separation and quantification of silver nanoparticles and silver ions using reversed phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry in combination with isotope dilution analysis N2 - A reversed phase high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICP-MS) approach in combination with isotope dilution analysis (IDA) for the separation and parallel quantification of nanostructured and ionic silver (Ag) is presented. The main focus of this work was the determination of the ionic Ag concentration. For a sufficient stabilization of the ions without dissolving the nanoparticles (NPs), the eluent had to be initially optimized. The determined Ag ion concentration was in a good agreement with results obtained using ultrafiltration. Further, the mechanism of the NP separation in the HPLC column was investigated. Typical size exclusion effects were found by comparing results from columns with different pore sizes. Since the recovery rates decreased with increasing Ag NP size and large Ag NPs did not elute from the column, additional interactions of the particles with the stationary phase were assumed. Our results reveal that the presented method is not only applicable to Ag NPs, but also to gold and polystyrene NPs. Finally, IDA-HPLC-ICP-MS experiments in single particle mode were performed to determine the particle cut-off size. The comparison with conventional spICP-MS experiments resulted in a similar diameter and particle size distribution. KW - ICP-MS KW - Silver nanoparticles KW - HPLC KW - Isotope dilution analysis KW - Field flow fractionation KW - Toxicology PY - 2016 U6 - https://doi.org/10.1016/j.chroma.2016.09.028 SN - 0021-9673 VL - 1468 SP - 102 EP - 108 PB - Elsevier B.V. AN - OPUS4-38642 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -