The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Steffen M Weidner - One of the best experts on this subject based on the ideXlab platform.
-
matrix assisted laser desorption ionization time of flight mass spectrometric imaging of synthetic Polymer Sample spots prepared using ionic liquid matrices
Rapid Communications in Mass Spectrometry, 2014Co-Authors: Stefan J Gabriel, Dietmar Pfeifer, Clemens Schwarzinger, Ulrich Panne, Steffen M WeidnerAbstract: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 (1) H 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.
Hajime Ohtani - One of the best experts on this subject based on the ideXlab platform.
-
end group analysis of styrene butyl acrylate coPolymers initiated with benzoyl peroxide by stepwise chemolysis pyrolysis gas chromatography
Journal of Analytical and Applied Pyrolysis, 2017Co-Authors: Hajime Ohtani, Kaoru Takeuchi, Yoshinori Iiguni, Asako Kaneko, Masaaki Kiura, Hikaru MomoseAbstract:Abstract End groups in a series of styrene (St)-butyl acrylate (BA) coPolymer Samples (St:BA, 80:20 molar feed ratio) prepared through radical Polymerization with various amounts (1.5–10 wt%) of benzoyl peroxide (BPO) as an initiator were characterized. Two types of end groups originated from the BPO initiator—benzoyloxy and phenyl terminal groups—were individually determined by stepwise chemolysis-pyrolysis gas chromatography (Py-GC) using a double-shot furnace pyrolyzer. In the first (chemolysis) step, the coPolymer Sample was mixed with tetramethylammonium hydroxide and introduced into the pyrolyzer at 250 °C for 10 min. During this step, the benzoyloxy terminal groups were selectively and quantitatively decomposed into methyl benzoate through the thermally assisted hydrolysis and methylation of ester linkages, which was clearly observed in the pyrogram. In the second step, the residual Polymer Sample was analyzed by ordinary Py-GC at 600 °C. In the observed pyrogram, benzene and C 14 H 12 were separately detected as the key products reflecting the phenyl terminal groups among the various pyrolyzates of the Polymer main chain. Based on the peak intensities of these characteristic products, the relative contents of both types of the end groups from BPO were estimated to be almost proportional to the feed amounts of BPO. Moreover, it was determined that the number of benzoyloxy end groups was roughly twice of that of the phenyl terminal groups.
-
development of new pyrolysis gc ms system incorporated with on line micro ultraviolet irradiation for rapid evaluation of photo thermal and oxidative degradation of Polymers
Polymer Degradation and Stability, 2009Co-Authors: Chuichi Watanabe, Shin Tsuge, Hajime OhtaniAbstract:Abstract A new pyrolysis–GC/MS system incorporating with on-line micro-ultraviolet (UV) irradiation was developed to make rapid evaluation of the synergistic material deterioration during UV irradiation under thermal and oxidative atmospheres. The basic effectiveness of the system was demonstrated by polystyrene, polypropylene and polycarbonate as the test Samples. The volatile products evolved during deterioration of the Polymers were analyzed on-line by thermal desorption GC/MS, and then the residual degraded Polymers were analyzed by evolved gas analysis (EGA) and/or Py–GC/MS to obtain specific thermograms and pyrograms. Based on these results, the deterioration mechanism of the Polymeric materials during irradiation under thermal and oxidative atmosphere can be evaluated using a sub-milligram Polymer Sample within a relatively short period of time.
Ulrich Panne - One of the best experts on this subject based on the ideXlab platform.
-
matrix assisted laser desorption ionization time of flight mass spectrometric imaging of synthetic Polymer Sample spots prepared using ionic liquid matrices
Rapid Communications in Mass Spectrometry, 2014Co-Authors: Stefan J Gabriel, Dietmar Pfeifer, Clemens Schwarzinger, Ulrich Panne, Steffen M WeidnerAbstract: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 (1) H 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.
Charles L Wilkins - One of the best experts on this subject based on the ideXlab platform.
-
determination of molecular weight distributions of Polymers by maldi ftms
Analytical Chemistry, 1995Co-Authors: Michael Dey, John A Castoro, Charles L WilkinsAbstract:The advantages of matrix-assisted laser desorption/ionization (MALDI) and Fourier transform mass spectrometry (FTMS) are combined to create a powerful tool for the characterization of power Samples. MALDI permits generation of intact, singly charged, high-mass (m/z 10 3 -10 4 ) ions of polar and nonpolar analytes, while GTMS provides unique high resolution and mass accuracy. Use of a gated deceleration potential allows for FTMS detection of MALDI-generated ions. However, when a single delay time is used between desorption/ionization and restoration of normal trapping potentials, mass discrimination is apparent for broad power distributions. Here, an integral method for obtaining molecular weight distributions of Polymers by MALDI-FTMS is presented. By means of a simple procedure of averaging time domain transients obtained from a series of Polymer Sample spectra recorded at systematically varied gated deceleration times, accurate power distributions are obtained. The technique is demonstrated with several poly(ethylene glycol) Samples containing oligomers with masses covering a 10 kDa mass range
Joseph A Gardella - One of the best experts on this subject based on the ideXlab platform.
-
spatial analysis of time of flight secondary ion mass spectrometric images by ordinary kriging and inverse distance weighted interpolation techniques
Analytical Chemistry, 2008Co-Authors: Tammy M Milillo, Joseph A GardellaAbstract:Ordinary kriging and inverse distance weighted (IDW) are two interpolation methods for spatial analysis of data and are commonly used to analyze macroscopic spatial data in the fields of remote sensing, geography, and geology. In this study, these two interpolation techniques were compared and used to analyze microscopic chemical images created from time of flight−secondary ion mass spectrometry images from a patterned Polymer Sample of fluorocarbon (CxFy) and poly(aminopropyl siloxane) (APS, a.k.a. siloxane). Data was eliminated from the original high-resolution data set by successive random removal, and the image file was interpolated and reconstructed with a random subset of points using both methods. The statistical validity of the reconstructed image was determined by both standard geographic information system (GIS) validation statistics and evaluating the resolution across an image boundary using ASTM depth and image resolution methodology. The results show that both ordinary kriging and IDW techni...