Mass spectrometry polymer characterization using

Polymers are not easily converted to gas-phase ions but this is a requirement for compounds analyzed by mass spectrometry. Despite this difficulty, mass spectrometry has been utilized to study various aspects of polymers polymers can be characterized - among others - with respect to their chemical composition, to their end groups, and to their molecular weight. Moreover, mass spectrometry can be used to study polymer surfaces. 

Applications of FAB have been succesfully performed in the characterization of a wide range of compounds (dyes, surfactants, polymers...) but little attention has been devoted to the capabilities of this technique to solve environmental concerns, such as organic pollutants identification in water. The widespread use of surfactants in the environment has required the emplo yment of both sensitive and specific methods for their determination at trace levels. GC/MS and HPLC procedures has been used for the determination of anionic (LAB s) and non ionic surfactants (NPEO) in water (1-4). Levsen et al (5) identified cationic and anionic sirrfactants in surface water by combined field desorption/ collisionally activated decomposition mass spectrometry (FD/CAD), whereas FAB mass spectrometry has been used for the characterization of pine industrial surfactants (6-8). 

Large molecules, such as proteins and polymers, do not have the thermal stability to vaporize without decomposing. Desorption ionization sources permit the direct ionization of solids, facilitating the analysis of large molecules. There are several types of desorption sources in which solid samples are adsorbed or placed on a support and then ionized by bombardment with ions or photons. Desorption Cl, one form of desorption ionization, has aheady been described. The important technique of secondary ion mass spectrometry (SIMS) is used for surface analysis as well as characterization of large molecules SIMS is covered in detail in Chapter 14, Section 14.4. Several other important desorption sources are described subsequently. 

A variety of volatilization/ionization methods have been applied to polymers a recent review or key paper is cited here for each. Extensive reviews that include mass spectrometry of pol5mrers can be found in Analytical Chemistry Other to )ical reviews are field desorption, laser desorption, plasma desorption, fast-atom bombardment, pyrolysis, and electrospray ionization. The present review will focus on polymer characterization using secondary-ion mass spectrometry (SIMS) in the high mass range comparison with other methods will be presented where appropriate. 

McEwen, C, Jackson, C and Larsen, B, (1996) The fundamentals of characterizing polymers using MALDI mass spectrometry. Polym. Preprints (Am. Chem. Soc., Division of Polymer Chemistry), 37, 314-315. 

There are a number of detection options, some used primarily for GPC and others that have use for GPC as well as other modes of HPLC. The differential refractometer, viscometer, and light-scattering detectors are associated mostly with GPC, while absorbance detectors such as the UV/ visible or photodiode array (PDA) are widely used in all HPLC modes, including GPC. The UV/visible and PDA are especially useful for characterizing polymers and oligomers with chromophoric groups and for HPLC analyses of additives. Mass spectrometry is also used for some analyses. This is described in Sec. ILF. 

By far the largest, most successful applications of PGC have been to the characterization of synthetic polymer microstructure. PGCs of these compounds yield information such as monomer identity and content, purity, and presence of additives. PGC is even more powerful for solving these types of problems when coupled with spectroscopic detectors. For example, Sahota et al. (48) showed that single-step PGC coupled with mass spectrometry could be used to measure the DNA content of cultnred mammalian cells. 

The enormous temperatures attained on resistively heated sample holders can also be used to intentionally enforce the decomposition of non-volatile samples, thereby yielding characteristic pyrolysis products. Pyrolysis mass spectrometry (Py-MS) can be applied to synthetic polymers, [54] fossil biomaterial, [55] food [56] and soil [57] analysis and even to characterize whole bacteria. [58]... 

A frequent complication in the use of an insoluble polymeric support lies in the on-bead characterization of intermediates. Although techniques such as MAS NMR, gel-phase NMR, and single bead IR have had a tremendous effect on the rapid characterization of solid-phase intermediates [27-30], the inherent heterogeneity of solid-phase systems precludes the use of many traditional analytical methods. Liquid-phase synthesis does not suffer from this drawback and permits product characterization on soluble polymer supports by routine analytical methods including UV/visible, IR, and NMR spectroscopies as well as high resolution mass spectrometry. Even traditional synthetic methods such as TLC may be used to monitor reactions without requiring preliminary cleavage from the polymer support [10, 18, 19]. Moreover, aliquots taken for characterization may be returned to the reaction flask upon recovery from these nondestructive... 

Even if relatively new, HF FIFFF has been used to separate supramicrometer particles, proteins, water-soluble polymers, and synthetic organic-soluble polymers. Particle separation in HF FIFFF has recently been improved, reaching the level of efficiency normally achieved by conventional, rectangular FIFFF channels. With these channel-optimized HF FIFFF systems, separation speed and the resolution of nanosized particles have been increased. HF FIFFF has recently been examined as a means for off-line and on-line protein characterization by using the mass spectrometry (MS) through matrix-assisted laser desorption ionization time-of-flight mass spectrometry (M ALDl-TOF MS) and electrospray ionization (ESl)-TOF MS, as specific detectors. On-line HF FIFFF and ESl-TOF MS analysis has demonstrated the viability of fractionating proteins by HF FIFFF followed by direct analysis of the protein ions in MS [38]. 

Finally, another method commonly used to characterize these copolymeric materials is that of matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. When using this technique, it is possible to investigate the molecular weight distributions, end groups, and polymer constitution of low-molecular-weight samples [63], MALDI-TOF may also provide vital... 

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