Matrix-assisted laser desorption/ionization molar masses

Mass spectroscopy is a useful technique for the characterization of dendrimers because it can be used to determine relative molar mass. Also, from the fragmentation pattern, the details of the monomer assembly in the branches can be confirmed. A variety of mass spectroscopic techniques have been used for this, including electron impact, fast atom bombardment and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy. 

C. Puglisi, F. Samperi, S. Carroccio, and G. Montaudo. Analysis of Poly(bisphenol A Carbonate) by Size Exclusion Chromatography/Matrix-Assisted Laser Desorption/ Ionization. I. End Group and Molar Mass Determination. Rapid Communications in Mass Spectrometry, 13(1999) 2260-2267. 

MALDI-MS refers to matrix-assisted laser desorption-ionization mass spectroscopy, It is also called MALFI-TOF, because the mass spectrometer is a time-of-flight version. In this technique, the polymer is mixed with a molar excess of a salt, for cationization, and deposited on a probe surface. A UV laser is pulsed... 

RP-18 column and an eluent composition of acetonitrile-water 70 30 v/v, a technical alkoxy PEO is separated into the PEG, C13H27- and CijHai-PEO fractions. In addition to the functionality separation, within the functionality fractions a separation into oligomers is obtained. After identification of the peaks by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), the molar masses of the individual fractions are calculated via a conventional SEC calibration [33]. 

Montaudo, G., Montaudo, M.S., Puglisi, C., and Samp>eri, F., Molar Mass Distribution and Hydrodjmamic Interactions in Random Copolyesters Investigated by Size Exclusion Chromatography Matrix Assisted Laser Desorption/Ionization, Macromolecules, 31, 3839 (1998). 

The introduction of Matrix-Assisted Laser Desorption/Ionization (MALDI) and Electrospray Ionization (ESI) (Chapter 1) has dramatically increased the mass range for molar mass analyses by mass spectrometry. In principle, both techniques are able to produce intact quasi-molecular ions of polymers with high molar mass (>100,000 Da). 

Karas, M., Bahr, U., Deppe, A., Stahl, B., and Hillenkamp, R, Molar Mass Determination of Macromolecular Compounds by Matrix-assisted Laser Desorption Ionization Mass Spectrometry Makromol. Ghent., Macrontol. Symp., 61, 397,1992. 

Pasch, FI. and Rode, K., Use of Matrix-assisted Laser Desorption/Ionization Mass Spectrometry for Molar Mass-sensitive Detection in Liquid Chromatography of polymers, /. Chromatogr., 699, 21, 1995. 

S.T., and Owens, K.G. (2005) Molar mass distributions of polymers from size exclusion chromatography and matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry methods for comparison. J. Appl. Polym. Set, 97, 627-539. 

The properties of polycarbonate beside its molar mass distribution (D=Mw/Mn) depend often of type and amount of end groups, cycles, additives and branch. In particular the end chains constitute the fingerprints of its polymerization procedure, of its thermal and mechanical history and of their environmental use. Several tools such as NMR, FT-IR and Mass Spectrometry were used to determine these peculiar characteristics of PC. In particular the matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has successfully been applied to obtain these information (49,50). MALDI-TOF technique is able to look each molecule even in a complex mixture (51-53), to obtain information on the end groups and structure (linear, cyclic or branched) of the macromlecular chains as a function of the synthesis and processing conditions. 

Molar weight of the dendrimers measured by MALDl-TOF (matrix assisted laser desorption ionization-time-of-flight mass spectrometry)... 

Pasch H, Rode K. Use of matrix-assisted laser-desorption/ionization mass-spec-trometry for molar mass-sensitive detection in Uquid-chromatography of polymers. J Chromatogr A 1995 699 21-9. 

The use of MALDI (Matrix-Assisted Laser Desorption Ionization) equipped with a time of flight (TOP) spectrometer offers an elegant and effective method for the precise and absolute determination of polymer molar masses. Initially designed for the characterization of biomolecules, MALDI-TOF spectrometry is now extensively applied to synthetic polymers in this technique the polymer to be studied is dispersed in an organic matrix that is volatilized under the effect of a laser radiation whose wavelength is in the absorption range of the matrix. Owing to the specific molecular interactions between polymer and matrix—which plays an important role in the chain desorption—each polymer requires a suitable matrix. For example, 1,8,9-trihydroxyanthracene is well suited to poly(methyl methacrylate). 

Pasch, H., K. Rode, Matrix-assisted laser desorption/ionization MS for molar mass-sensitive detection in LC of polymers, / Chromatogr. A, 1995,699, 21-29. 

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