LD-FTMS spectra

A simple example of the use of LD/FTMS for surface analysis may be found in the analysis of blue stain on the surface of a copper part. In order to determine the nature of the stain, we obtained LD/FTMS spectra for samples of both stained and unstained copper. Both samples were mounted on the automatically rotated sample insertion probe on the FTMS-2000. The samples were rotated after each laser shot to expose a fresh surface at the laser focus. Approximately twenty-five laser shots were signal averaged for each spectrum, in order to increase signal-to-noise, and to provide a spectrum which would represent the averaged composition of the surface. 

Determinations of MM in relatively low MM polymer samples (up to a mass limit of about 10,000 Da) have appeared in the last decades, by a number of soft ionization MS techniques as static SIMS-TOF, LD-FTMS, DCC FD, FAB, ESI. The ESl-TOF technique, which for proteins is capable of providing high MM measurements, in the case of synthetic polymers yields spectra only below 5000 Da, due to chain entanglement. ... 

Figure 1.13 Comparison of positive ion spectra of DLTDP acquired by (a) FAB, (b) CO2 LD-FTMS and (c) Nd YAG LD-FTMS Reproduced from Johlman and co-workers, American Chemical Society [63]...

Wilkins et al. [210] have used LD-FTMS to characterise a series of synthetic linear epoxypolyacenes, which are difficult to analyse by FAB due to then-limited solubility. In this case, electron ionisation leads to extensive decomposition LD-FTMS yields abundant molecular ions and some fragment ions in the negative ion spectra. Similarly, LD-FTMS has been used to analyse intractable solids such as poly(jn-phenylene)s (PPP) [211] and conducting heterocyclic polymers. Kotsuka et al. [190] have given other examples for LD-FTMS for PDMS, Oxypruf-20, and PPG. 

An interesting method was presented for the analysis of perfluorinated polyethers (PFPE) by Cromwell et al. The fluorinated polymers are commonly used as lubricants because of their low vapor pressures, chemical inertness, and thermal stability. Samples were examined in a cubic trap FTMS-2000 system using a 4.3 T magnetic field. Both a Kr/F excimer laser and a Nd/YAG laser were used for infernal LD. The fwo-step procedure involved using the 248-nm excimer laser for desorption of the polymer and, immediately following, a second more tighfly focused 532 nm laser ablation pulse to ablate metal cations from fhe surface beneath the polymer sample. Thus, cationization could be controlled, and the dynamics of the process are discussed. Mass spectra extended up to 10,000 Da are shown. 

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