Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is an important technique to characterize many different materials, including synthetic polymers. MALDI mass spectral data can be used to determine the polymer average molecular weights, repeat units, and end groups. One of the key issues in traditional MALDI sample preparation is making good solutions of the analyte and the matrix. Solvent-free sample preparation methods have been developed to address these issues. Previous results of solvent-free or dry prepared samples show some advantages over traditional wet sample preparation methods. Although the results of the published solvent-free sample preparation methods produced excellent mass spectra, we found the method to be very time-consuming, with significant tool cleaning, which presents a significant possibility of cross contamination. To address these issues, we developed an extension of the solvent-free method that replaces the mortar and pestle grinding with ball milling the sample in a glass vial with two small steel balls. This new method generates mass spectra with equal quality of the previous methods, but has significant advantages in productivity, eliminates cross contamination, and is applicable to liquid and soft or waxy analytes. (J Am Soc Mass Spectrom 2005, 16, 90 -93)

The results of fast atom bombardment (FAB), time-of-flight secondary ion mass spectrometry (ToF-SIMS), matrix-assisted laser desorption/ionization (MALD/I), electrospray ionization (ESI), and field desorption (FD) analyses of ethoxylated oligomers of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Surfynol(®) 104) were compared.Each of these desorption mass spectrometry (MS) techniques can produce spectra of unfragmented cationized oligomers. From the observed ion series we calculate average molecular weight information. We have compared the results of mass spectrometric analyses of a series of ethoxylated Surfynol surfactants. Our data indicate that FAB, ToF-SIMS, MALDI/I, and ESI produce similar results for the lower molecular weight species, but that as the average molecular weight increases FAB and SIMS produce slightly lower results than MALD/I and FD. This could be due to increased fragmentation. ESI produced a result similar to FAB and SIMS for the highest average molecular weight material. Further experiments compare the mass spectral results with gas chromatographic quantitative data. Although gas chromatography is not expected to accurately analyze the higher mass oligomers, we observe significant differences in intensities of the short-chain oligomers (especially the 0- and 1-mers) when compared to the desorption mass spectrometer results. These differences may reflect poor cationization efficiency for very short oligomer chains in the mass spectrometric analyses.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has become an important technique to characterize the chemical structure of industrial polymer materials. MALDI methods have been developed to address a broad variety of different polymer materials containing different chemistries. One of the key aspects of the typical MALDI experiment is the generation of intact ions. The development of Atmospheric Pressure (AP) MALDI quadrupole ion trap (QIT) instruments has opened another channel to obtaining MS/MS experiments for polymer samples. These experiments provide a new method to obtain chemical structure information from MALDI experiments. Collision-Induced Dissociation (CID) provides an improved MALDI MS/MS experiment that can be done on readily available mass spectrometers. AP MALDI QIT techniques have been successfully applied to a variety of synthetic polymers. This work explores the applicability of AP MALDI QIT methods to relatively low molecular weight ethoxylated surfactants. In these experiments we show the CID fragmentation mass spectra on some ethoxylated surfactants, and demonstrate the existence of analyte matrix clusters. [5][6][7]. MALDI can generate important data on the telomer repeat units, end groups, and average molecular weights of these materials. MALDI methods have been developed to address a broad variety of different polymer materials containing different chemistries. One of the key aspects of the typical MALDI experiment is the generation of intact ions. MALDI mass spectra generally show little fragmentation. The production of intact ions is vital for the quantitation of average molecular weights, but limits the amount of chemical structural information that can be obtained from the data.The development of MALDI post-source decay (PSD) techniques has opened a new method to obtain chemical structure information from MALDI experiments [8 -10]. Unfortunately, PSD experiments are relatively crude MS/MS experiments. The range of masses submitted for the fragmentation is broad, the mass resolution and mass accuracy of the fragment spectra is not as good as the MALDI data, and there is very limited control of the energy deposition into the fragmentation process.The development of atmospheric pressure (AP) MALDI instruments has enabled the utilization of different mass analyzers for MALDI [11,12]., One of the key benefits to changing the mass analyzer in a MALDI experiment is to significantly improve the MS/MS capability. A quadrupole ion trap (QIT) mass spectrometer is an excellent choice in this regard. Some early work showed examples of high quality MS/MS experiments on MALDI generated peptides [13][14][15][16]. The ability to analyze synthetic polymers using AP MALDI methods on a QIT have also been demonstrated [17].With a QIT mass spectrometer we can accomplish high quality collision-induced dissociation (CID) MS/ MS. The instrument is capable of selecting an individual ion from the mass spectrum for fragmentation. The fragmentation gas and relative energy can be controlled...

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One-dimensional nuclear magnetic resonance (NMR) Is a valuable tool for structural elucidation of perfluorinated materials. The value of ieF 1-D NMR diminishes, however, In multicomponent systems due to rapidly Increasing spectral complexity. The alternative of separatlon/purtflcatlon of these complex liquid mixtures can be prohibitively costly and time consuming. Physical-chemical property similarities potentially prohibit component purification using standard chromatographic techniques. The application of two-dimensional 19F NMR techniques to complex perfluorinated liquid mixtures has provided previously unobtainable Information about the number and structure of components. The Impact of homonuclear Hartmann Hahn (HOHAHA) and homonuclear relayed coherence transfer (COSYRCT) on component Identification In Isomer mixtures was explored. With component Identification and subsequent 1-D 19F spectral assignments completed, quantitation via routine methods could be performed. The ability to extract one-dlmenslonal 19F spectra of "pure" Individual components from both the 2-D HOHAHA and COSYRCT experimental spectra and their unique advantages, disadvantages, and limitations as tools for spectroscopic separation of complex liquid mixtures were demonstrated.

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Two fragmentations of (CH3)3SiO-CR2-X-CR2-OSi(CH3)3, where X is a rigid group such as a triple bond or an aromatic ring, are losses of a methyl or R group (where R is H or alkyl). The metastable-ion dissociations of [M-R]+ and [M-CH3]+ ions include the rearrangement of a trimethylsilyl (TMS) cation and a (CH3)2Si = O neutral species through an ion-neutral complex. On the basis of tandem mass spectrometry (MS/MS), exact mass measurement and isotopic labeling experiments, it has been established that the two trimethylsilyloxy groups in the TMS ethers interact across a wide range of distances via an ion-neutral complex. The migration of a TMS cation occurs when the group that is bound to carbon is expelled as a radical by an oxygen-directed cleavage to give a trimethylsilylated oxonium ion. If, on the other hand, a methyl radical is lost from the silicon atom, then (CH3)2Si = O migrates. The mobilities of the TMS cation and the neutral (CH3)2Si = O are governed by the capability of the rigid group to delocalize charge.