Laser ablation mass spectrometry , polymer

The nanostructuring is achieved by directing a pulse from a frequency-tripled Nd YAG laser with a pulse width of 35 ps, a wavelength of 355 nm, and up to 250 pj pulse energy through a near-field optical tip. The tip had a diameter aperture of around 170 nm, creating ablation craters with about the same diameter (see below). Molecular crystals (the same bis-triazene that was used as model compound for the triazene polymers in other studies, shown in Scheme 7) were applied as substrates, because the main goal of this study was the development of nanoscale atmospheric-pressure laser ablation-mass spectrometry [390]. 

Ruch, D., Boes, C., Zimmer, R., Migeon, H.-N., Muller, J.-F. (2003) Surface oxidation of styrene butadiene copolymers study by laser ablation and secondary ion mass spectrometry. Journal of applied Polymer Science, 87,1910-1917. Ruch, D., Muller, J.-E, Migeon, H.-N., Boes, C., Zimmer, R. (2003) Secondary ion and laser ablation mass spectrometry... 

Applications employing laser ablation of polymers include film deposition and the synthesis of certain organic compounds. Laser beam ablation in conjunction with mass spectrometry is an important tool for polymer analysis, which is referred to as laser desorption mass spectrometry (LDMS). One particular type of LDMS, termed matrix-assisted laser desorption/ionization (MALDI), has contributed essentially to the analysis of proteins (Nobel prize for chemistry to K. Tanaka in 2002) [126,127]. Further information on this subject is available in Ref [4]. 

Dobney AM. Mank AJG, Conneely P, Grobecker K-H, de Roster CG (2000) Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a tool for studying heterogeneity within polymers. Submitted for publication... 

Among the various mass spectrometry techniques, MALDI is probably the most important as it provides an absolute method for molar mass determination and molar mass distribution, as well as information on end groups and copolymer composition. The MALDI process consists of the ablation of the polymer molecules dispersed in a matrix typically made up of aromatic organic acids. The matrix needs to be able to absorb at the wavelength of a laser (usually 337 nm). This process excites the matrix molecules, which vaporize at the same time, the polymer molecules desorb into the gas phase, where they are ionized. Thus, the role of the matrix is that of transferring the laser energy to the polymer molecnles. 

Resano, M., Garcfa-Ruiz, E., Vanhaecke, E (2005) Laser ablation-inductively coupled plasma-dynamic reaction cell-mass spectrometry for the multi-element analysis of polymers. Spectrochimica Acta Part B, 60,1472-1481. 

Analytical pyrolysis coupled to mass spectrometry is widely used for identification of thermal decomposition products of polymers, and pyrolysis reaction mechanisms are frequently postulated on the basis of the products obtained. PyMS, in its simplest form, compared to other more sophisticated techniques, such as direct FIMS, laser ablation-MS, and FAB, already provides data which, with sufficiently wide databases, can give useful information about structure. Zoller et al [706] analysed the polymer structure of LLDPF/30 wt.% CB and LLDPF/20 wt.% silica by means of Py-PIMS. The mass spectrum of LLDPF/CB was indistinguish-... 

Rabek [51] and others [52] have described laser-induced decomposition of polymers. Comprehensive reviews have appeared on the interaction of laser radiation with solid materials and its significance in analytical chemistry [53,53a]. Various reviews cover the subjects of optical and mass spectrometry performed directly on the laser plume [54,55]. Moenke-Blankenburg [38] has described laser ablation for sample introduction. Advances in laser ablation of materials were recently reported [56,57]. 

Due to their extremely low concentration, the identification and quantitative determination of the molecular groups located at the chain ends is very difficult. Mass spectrometry by ablation of a matrix in which the polymer is dispersed by a laser radiation (MALDI) has opened very promising prospects for the resolution of this problem (see Section 6.3). 

Gill, C. G. and Blades, M. W. (1993) Laser ablation ion-trap mass-spectrometry - atomic and molecular mass-spectrometry of metal, ceramic and polymer samples. J. Anal. At. Spectrom., 8(2), 261-7. 

---